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Arousal and memory

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Title:
Arousal and memory effects of aging
Alternate title:
Effects of aging
Creator:
Schramke, Carol Joann, 1959-
Publication Date:
Language:
English
Physical Description:
vi, 106 leaves : ill. ; 29 cm.

Subjects

Subjects / Keywords:
Age groups ( jstor )
Amnesia ( jstor )
Anxiety ( jstor )
Cognitive psychology ( jstor )
Lesions ( jstor )
Memory ( jstor )
Memory retrieval ( jstor )
Older adults ( jstor )
Psychology ( jstor )
Psychophysiology ( jstor )
Aging ( mesh )
Arousal -- physiology ( mesh )
Department of Clinical and Health Psychology thesis Ph.D ( mesh )
Dissertations, Academic -- College of Health Related Professions -- Department of Clinical and Health Psychology -- UF ( mesh )
Memory, Short-term ( mesh )
Mental Recall -- Adult ( mesh )
Mental Recall -- Aged ( mesh )
Psychophysiology ( mesh )
Research ( mesh )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Thesis (Ph.D.)--University of Florida, 1990.
Bibliography:
Bibliography: leaves 97-105.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Carol J. Schramke.

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Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
025784781 ( ALEPH )
24641677 ( OCLC )
AHK5059 ( NOTIS )

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Full Text














AROUSAL AND MEMORY: EFFECTS OF AGING


By

CAROL J. SCHRAMKE










A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


1990




AROUSAL AND MEMORY: EFFECTS OF AGING
By
CAROL J. SCHRAMKE
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1990


ACKNOWLEDGEMENTS
This dissertation is dedicated to my maternal
grandmother, Frances Gendregske Frost, who cannot understand
why my studies are so important to me, but loves me
unconditionally nevertheless. Many thanks must go to my
husband, Carson Lane, who has moved from Michigan to Florida
and then to Oregon with few complaints and who encouraged me
and believed in me whenever I needed his support. I am also
indebted to the many older adults who were enthusiastic
about my project and my interest in aging and who braved the
horrible parking situation at Shands in order to participate
in my research. Finally, I am grateful to Beverly
Funderburk, who was my legs when I was 3,000 miles away,
making the completion of this endeavor possible.
I am also wish to acknowledge my committee members Walt
Cunningham, Jaber Gubruim, Kenneth Heilman, Michael
Robinson, Robin West, and especially Russell Bauer, my
chair, for their patience and their assistance in making
this a better research project. This research was funded,
in part, by NIMH National Research Fellowship Award Number
5F31MH09640-02.
ii


TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS iv
ABSTRACT V
BACKGROUND 1
Introduction 1
Aging and Memory 4
Aging and Arousal 10
Arousal and Memory: Interactions 13
Changes in Brain Physiology with Aging 18
Neuropsychological Mechanisms in Aging and Memory.. 20
Aging, Arousal, and Memory 28
EXPERIMENT 1: METHODS 31
Induced Amnesia for Pictures Before and After a
Critical Event: Overview and Rationale 31
Subjects 3 2
Materials 33
Procedure 35
EXPERIMENT 1: RESULTS 3 8
Psychometric Test Performance 3 8
List Effects 42
Overall Recall and Recognition Performance 4 3
Effect of Item Position and the
Critical Event on Memory 44
Response Types 52
Electrodermal Recognition of Recognized
and Unrecognized Targets 55
EXPERIMENT 1: DISCUSSION 58
EXPERIMENT 2: METHODS 65
The Interaction of Age and Increased Tonic Arousal
on a Supraspan List Learning Task: Overview and
Rationale 65
Subjects 67
iii


Experimental Conditions 67
Materials and Apparatus 67
Procedure 69
EXPERIMENT 2: RESULTS 71
Psychometric Test Performance 71
Free Recall, Cued Recall, and Recognition 72
Effects of Exercise, Rest, and Distractor Tasks
on Measures of Arousal 74
Exercise Condition and Memory 78
EXPERIMENT 2: DISCUSSION 81
GENERAL DISCUSSION 84
APPENDICES
A Screening Questionnaire 93
B Modified California Verbal Learning Test 95
REFERENCES 97
BIOGRAPHICAL SKETCH 106
iv


Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
AROUSAL AND MEMORY: EFFECTS OF AGING
By
Carol J. Schramke
August 1990
Chairman: Russell M. Bauer, Ph.D.
Major Department: Clinical and Health Psychology
These studies examine the influence of phasic and tonic
arousal on memory performance in younger and older adults.
Subjects in Experiment One were asked to learn a list of 25
simple line drawings during Session One and 24 drawings with
a unique item (i.e., the critical event) in the center
position (photograph of either a normal or starving child)
during Session Two. Previous research has demonstrated that
younger adults' memory for a critical event increases, while
memory for items surrounding the critical event is
disrupted, presumably because of phasic arousal elicited by
the distinctive item. This phenomena had not been
replicated with older adults. In this study, while both
younger and older adults demonstrated increased recall of
v


the critical event, only younger adults' recall for
surrounding stimuli was disrupted. Younger adults also
demonstrated greater disruption in memory when the
photograph was subjectively more disturbing (i.e., emaciated
rather than normal child), while older adults showed similar
memory patterns for surrounding items regardless of the
nature of the center item.
In the second study, state dependent learning was
examined by manipulating physiologic arousal. Subjects
either rested or exercised immediately prior to learning a
modified version of the California Verbal Learning Test, and
then engaged in either the same or the alternate activity
immediately prior to delayed recall. Both younger and older
adults showed clear state dependent learning effects, as
well as increased semantic clustering, when in the same
state at both acquisition and recall. Age by type of memory
test interactions were found in both studies, with age
differences on recall but not recognition tasks. No age by
arousal state interactions were suggested; young and old
were equally affected by state dependent learning, and
neither group was affected by overall level of arousal
during the learn or recall phase. Brain areas implicated as
important in explaining the age differences and similarities
found include the amygdala, frontal lobes, and hippocampus.
vi


BACKGROUND
Introduction
Neuropsychology has traditionally studied brain changes
resulting from brain injury or diseases of the brain and
attempted to provide guidelines for separating normal
variation in performance from variations induced by brain
pathology. In studying aging, neuropsychologists can
contribute by clarifying the differences and similarities in
performance between young and old and by speculating as to
what brain changes these behavioral findings suggest.
Normal aging is associated with changes in both the brain
and behavior; exploring these changes offers an opportunity
for understanding how the brain influences behavior.
This paper will focus on aging and how it influences
memory and arousal. This will be accomplished by describing
the behavioral changes that have been associated with aging
in memory and arousal, how memory and arousal are believed
to interact in normal young adults, which brain areas are
believed to be most important for memory and arousal, and
reviewing why the brain changes associated with aging may
alter this interaction. Two studies that examine how memory
performance in young and old is influenced by manipulations
1


2
in arousal are then described. Finally, the implications of
these studies for understanding the neuropsychology of
memory and aging will be discussed.
Arousal has been conceptualized, and will be discussed
herein, as an index of attention or processing and as an
index of the state of an individual. Arousal, in the
neurological literature, is often associated with cortical
desynchrony that can be measured by electroencephalography.
This activation may be linked with an alteration in
affective state. Although it has been suggested that
physical arousal and an alteration in cognitive state are
necessary for the normal experience of emotion, an
alteration in arousal is not believed to be sufficient to
induce an emotional state (Schacter & Singer, 1962, Heilman,
Watson, & Bowers, 1983).
In the psychological literature arousal has been
conceptualized in a number of different ways. For example,
Eysenck (1976) defines arousal as an elevation in body
function that is both nonspecific and noninformational. He
acknowledges that conceptually arousal can be separated into
electrocortical, autonomic, and behavioral arousal, while
arguing that it can also be treated as a unitary phenomenon
and has been so treated historically. Psychological studies
of arousal have relied on indicators such as changes in
heart rate, skin conductance response, and blood pressure to
verify alterations in activation; no studies to date have
examined what effects this alteration in physical arousal


3
has on cortical activity, except through task performance.
The physical activation resulting from exercise has been
shown to have effects on performance of many cognitive tasks
(Tomporowski & Ellis, 1986), although there is no
verification in these studies that electrocortical activity
is systematically altered.
Although increasing or decreasing different types of
arousal may produce similar performance effects, there is
sufficient evidence to argue against treating arousal as a
unitary concept. At a minimum arousal can be divided into
tonic versus phasic arousal and electrocortical versus
autonomic arousal. Electrocortical activation may also be
different if it is associated with processing rather than
orienting to a shocking or novel stimulus or if it reflects
an emotional response to a stimulus or situation.
Although these different types of arousal and how they
effect memory have been studied in young adults, patterns of
tonic and phasic arousal may change with age and could
influence memory in older adults differently than they do in
young adults. The age-related neurophysiologic changes
responsible for these alterations in arousal still need to
be determined, but also may be clarified through the study
of the behavioral differences between younger and older
adults.
Memory processes are known to change with age, and
memory studies have come to dominate psychological research
on aging (Poon, 1985). A review of the aging and memory


4
literature finds many theories about the nature of this
decline. Information-processing models, which examine
specific stages or processes necessary for memory, have been
used to examine the changes in memory of the elderly as well
as brain-injured populations. More general cognitive
functions, such as speed and one's ability to attend, are
also necessary for an individual engaging in the various
stages of information processing, and changes in these
functions may influence memory performance. Both processing
changes and alterations in attention and arousal have been
suggested as possible mechanisms to explain age-related
memory change.
Aging and Memory
Age-related alterations in memory include older adults'
general slowing, poorer performance on supraspan memory
tasks, and much worse performance on tasks requiring recall
rather than recognition when compared to younger adults
(Poon, 1985). Age differences in cross-sectional studies
can be minimized by instructing the elderly on techniques
that can improve memory (e.g., imagery) and by providing
organization of to-be-remembered material (Poon, 1985).
Most models and theories about these changes invoke
psychological or biological factors.
Psychological factors that have been suggested as
possible contributors to this decline in memory performance
include depression, anxiety, task familiarity, and levels of
motivation (Poon, 1985). An increased incidence of


5
depression among the elderly may interfere with performance
on memory tests or be related to increased memory complaints
(e.g., Niederehe & Camp, 1985; West, Boatwright, & Schleser,
1984). It also has been suggested that the elderly are less
proximally familiar with laboratory procedures or other new
learning tasks. Because of this they may analyze the tasks
differently and use a less efficient approach; or they may
view the tasks as more threatening, which could increase
their anxiety. Either of these factors could negatively
influence performance (Langer, Rodin, Beck, Weinman, &
Spitzer, 1979; Perlmutter, 1978). Although these factors
may contribute to poorer performance of the elderly on
laboratory tests of memory, Burke and Light (1981) argue
that these factors should affect all memory tasks
equivalently and they are not sufficient explanations to
account for the relatively select age differences found with
some memory tasks but not others.
In information-processing models, memory is typically
conceptualized as occurring in three stages: acquisition,
retention, and retrieval of information. Attempts to
isolate the memory difficulties associated with aging have
examined all three levels of this model. Because of the
difficultly in isolating each facet of the model, deficits
can often be explained by invoking more than one stage of
processing.
Evidence for acquisition deficits comes from studies
that show that older subjects do not spontaneously use


6
mnemonic strategies. These studies have shown that the
performance of older adults can improve, and age differences
can be minimized, when older adults are specifically
instructed to use these strategies (Rankin & Collins, 1985;
Thomas & Ruben, 1973 reported in Poon, 1984). For example,
in the Thomas and Ruben (1973) study, visual imagery
instructions, cartoon mnemonics (in which unusual
relationships between the stimulus and cue were depicted),
and a no-instruction condition were compared in a paired-
associate memory task. They found that the relatively large
differences between young and old seen under the no
instruction condition were greatly reduced when instructions
were provided. This suggests that older subjects benefit
more than the young when given instructions or organization
to assist in remembering.
Hess (1984) conducted two studies to examine
differences that result from manipulations at the
acquisition phase. In the first study, he presented
semantically related word pairs during the acquisition phase
(e.g., copper-iron) and during the test phase presented
either the same pair, a pair that suggested a new
interpretation of the test word (e.g., clothes-iron), or a
new context word that was similar to the original pair
(e.g., bronze-iron) in a yes/no recognition paradigm. In
the second study, word pairs were also presented but they
were all semantically unrelated. Hess found that older
adults used context information primarily when it activated


7
old learning (i.e., they did not recognize the target words
when the words were in the new context condition as well as
the younger subjects). Older subjects also had more false
positive errors for cues from the old context, making more
semantic confusion errors. This may reflect more general
and less distinctive encoding.
Results of Rabinowitz, Craik, and Ackerman's (1982)
study are also consistent with the hypothesis of less
distinctive encoding in the elderly. In this study, recall
for words to which subjects had previously generated their
own specific associates were compared to performance when
the associate or a general category cue was given during
retrieval. Older adults did not benefit as much from the
specific retrieval cues when compared with their younger
cohorts, but did equally well when provided with the more
generalized cues.
There is little evidence to support age-related
decreases in retention ability. Generally, researchers
interested in this phenomenon look for increased
interference, either proactive or retroactive, or an
increased rate of forgetting (Poon, 1985). These problems
have not been reliably demonstrated in the elderly (e.g.,
Poon and Fozard, 1980; Craik, 1977).
Proponents of a retrieval deficit theory often cite the
differences between performance on recall and recognition
tasks as supportive evidence. Young subjects do much better
on recall tests, while on recognition tasks older subjects


8
improve dramatically and the age difference in performance
levels is greatly minimized (Schonfield, 1965, Schonfield
and Robertson, 1966; Erber, 1974). It has been argued that
the older adults' ability to recognize information suggests
that the information is stored, so the problem must
therefore be one of retrieval. Poon (1985) contends it is
nearly impossible to separate retrieval problems from
acquisition difficulties, and differences between free
recall and recognition could also be explained by
inefficient encoding that would subsequently interfere with
retrieval. Poon (1985) notes that age differences can be
minimized if category cues are given at acquisition, but
these cues are not as effective when only given at the
retrieval stage. This finding leads him to argue that,
although retrieval deficits may be present, they are
probably not sufficient to account totally for the age
differences seen.
Other researchers have suggested that an age-related
slowing in performance that accompanies aging can account
for many changes in cognitive functioning, including changes
in performance on many memory tasks (e.g., Birren, 1974;
Salthouse, 1980). For example, it is noted that age
differences typically increase when time limitations are
given and are minimized when unlimited time is allowed
(Poon, 1985). Age-related slowing is noted to affect each
stage of information processing and could be responsible for
the differences seen between young and old at both


9
acquisition and retrieval (Salthouse and Somberg, 1982).
Supporters of this explanation argue that this provides one
of the most parsimonious explanations for the alterations
seen with aging, is a biologically based explanation that
should not be influenced by cohort effects, and can explain
why more complex cognitive tasks show more pronounced age
differences (Salthouse, 1985). However, although few would
argue that slowing does not influence memory performance, it
probably is not a sufficient explanation for all changes
seen in memory. Although memory differences between young
and old are typically increased when time limitations are
given, differences are maintained in many tasks even with
unlimited time. Speed explanations also have difficulty
accounting for some of the variable differences in different
types of memory tasks (Poon, 1985).
Although current findings are not conclusive, some
research suggests that part of the difference in memory
performance between young and old may be due to a difference
in response bias or response tendencies, with older adults
being more conservative. This response bias has been
demonstrated on both recall and recognition tasks, with
older adults being more likely to make errors of omission on
recall tasks and more likely to have false negative rather
than false positive errors on recognition tasks (Botwinick,
1984). Studies using signal detection analysis for
recognition of sensory stimuli have not consistently
supported the idea that older adults have a different


10
response bias (Botwinick, 1984). Memory studies, such as
Poon and Fozard's (1980) study on word recognition, have
provided some support for suggestions that older adults are
more cautious when responding in memory tasks, with older
adults in their study exhibiting a lower hit rate and
response sensitivity. The inconsistency of the research has
led some to argue that cautiousness cannot fully explain the
differences in memory performance, but differences in
response tendencies may contribute to differences in some
cases (Burke and Light, 1981).
Information processing and biological explanations for
the differences in memory performance between young and old
should not be viewed as separate from psychological and
cognitive theories. Some researchers have focused on the
patterns of cell loss to explain these deficits. This has
resulted in comparisons between normal aging and dementias,
as well as comparisons between normal aging and more focal
types of brain damage.
Aging and Arousal
Patterns of physiologic arousal are known to change
with increasing age. Woodruff (1985) and Marsh and Thompson
(1977) provide the most recent reviews of this literature.
A large number of studies have examined EEG changes and
aging. Woodruff (1985) summarizes the major findings from
these studies including changes in frequency and abundance
of alpha rhythm, changes in the incidence of beta activity,


11
diffuse slowing, focal slowing and abnormal activity in the
temporal lobes.
Autonomic nervous system changes also have been
documented. For example, changes in heart rate and
electrodermal skin conductance response that occur with
aging have frequently been used to argue for an under
arousal hypothesis of aging (Albert & Kaplan, 1980).
Classical conditioning studies using skin conductance
responses have shown the elderly to condition less readily
and extinguish more quickly (Botwinick & Kornetsky,
1959,1960). Older subjects also showed overall less
responsivity during the habituation period. Heart rate
deceleration in a warned reaction time procedure is believed
to be an index of filtering out irrelevant stimuli when
subjects are alert but relaxed while waiting for the
stimulus (Kahneman, 1973). In older subjects the magnitude
of the heart rate deceleration during the foreperiod is also
reduced, supporting the notion of under-arousal (Thompson &
Nowlin, 1973).
Woodruff (1985) notes, however, that many of these
studies involved passive responses to stimuli, and these
results may be quite different in situations calling for
active intentional processing. Kahneman (1973) points out
that demands on an individual's attention alters arousal,
while the level of arousal also influences how attention is
allocated. He cites the original Yerkes-Dodson studies
completed in 1908 that demonstrated that increased levels of


12
arousal improve performance on a learning task only up to a
point, and then additional arousal results in declines in
learning performance. Studies with sleep-deprived subjects,
who are considered under-aroused, typically show that
increasing motivation can improve performance to normal
levels (Kahnemen, 1973). This suggests that tonic arousal
and task demands interact to influence performance.
Others have suggested that the elderly are "over
aroused." Supporters of this hypothesis have relied on
biochemical measures of nervous system functioning such as
free fatty acid (FFA) in blood plasma, which is believed to
be highly correlated with the level of autonomic nervous
system activity (Woodruff, 1985). After stressful tasks the
elderly show greater FFA concentrations in comparison to
baseline measures than do the young, which led Eisdorfer,
Nowlin, and Wilkie (1970) to suggest that over-arousal
interferes with elderly performance. To test this
hypothesis they administered propranolol, an adrenergic
blocking agent, and tested an elderly population's memory
performance. They found better performance of elderly
subjects who received this drug compared with another group
who did not. However, there was no younger group with which
to compare performances, and a subsequent effort to
replicate this study using a within subjects design was
unsuccessful (Froehling, 1974) .
Studies attempting to manipulate arousal and to measure
the effects on elderly performance have produced mixed


13
results. Although not concerned with memory tasks per se,
Falk and Kline (1978) found that white noise selectively
impaired elderly performance on a critical flicker fusion
task. In contrast, Woods' (1980) study, in which body
position was used to increase arousal, found an older
group's performance was selectively enhanced on a reaction
time task. This difference may be due to the difference in
manipulations to increase arousal; arousal induced by
changes in body position may not be equivalent to change
induced by white noise.
Arousal and Memory: Interactions
Research on the interaction between arousal and memory
has a long and sometimes confusing history. Though arousal
has often been treated as a unitary phenomenon in the memory
literature, there are many important distinctions that
should be made. One of the most elementary distinctions in
arousal is the separation of event-related (phasic) arousal
from state (tonic) arousal (i.e. the overall activation
level of an organism). Phasic arousal refers to the
reaction of a organism to particular stimuli, while tonic
arousal refers to the resting (background) state of the
organism. It is also useful, within phasic arousal, to
distinguish between the arousal that indexes cognitive
processing, and the arousal that results from exposure to
highly shocking or emotional stimuli. Within tonic arousal
there may be differences in alterations induced by physical
activation, induction of mood states, and white noise.


14
Physiological arousal also may be separable from
electrocortical or central arousal.
The influence of phasic arousal on memory functions in
college students has been studied extensively, and fairly
consistent results have been obtained. Eysenck (1976,1977)
and Levonian (1972) provide reviews of this literature. In
the majority of studies the magnitude of phasic arousal at
acquisition has different effects on immediate and long-term
recall. Most studies use electrodermal skin conductance
response as the measure of phasic arousal, and find that low
arousal items are remembered best immediately but are not
recalled as well after a delay; high arousal items are not
recalled as well immediately but are recalled better after a
delay (e.g. Parkin, 1982, McLean, 1969, Levonian, 1967,
Kleinsmith & Kaplan, 1964,1963, Levinger & Clark, 1961). In
the few studies that did not produce this result, no
correction for order of presentation was instituted,
habituation to the testing situation was not achieved prior
to the start of presentation, or individual variation in
response to the stimuli was not taken into account
(Levonian, 1972).
In the earliest studies "arousal" was equated with
"emotion," and this memory pattern was interpreted as
"repression of trauma." In these studies emotional words
were used and suggested to be traumatic, but later studies
demonstrated that arousal from non-emotional stimuli could
also produce this pattern of recall (Eysenck, 1977). Most


15
recently, arousal during exposure to stimuli has been
suggested to represent the amount or depth of processing
that occurs and increased processing of arousing stimuli is
what causes the increase in delayed recall as well as
increased recognition (Pribram & McGuinness, 1975, Stelmack,
Plouffe, & Winogron, 1983). Information ultimately stored
in memory may not be as accessible immediately if the highly
arousing stimuli requires more time to be consolidated.
Other authors have focused attention on the interfering
effects of arousal on memory performance. The "von Restorff
effect" (Wallace, 1965) refers to the phenomenon in which
one novel stimulus embedded in a group of homogeneous items
is remembered better than other items (e.g. the word
"blood", embedded in a list of furniture items, will be
remembered better than the furniture items). In a variation
of this procedure Tulving (1969) demonstrated that the items
immediately preceding the novel stimulus were not remembered
as well as the other items more distant from the novel
stimulus. Tulving labeled this phenomenon "induced
retrograde amnesia" and likened it to retrograde amnesia
seen after trauma. This effect has been replicated with
both words and pictures, and it has been shown that the
amnesia can be seen for stimuli both immediately preceding
and following the novel stimuli (e.g. Saufley & Winograd,
1970, Schultz, 1971, Erdelyi & Blumenthal, 1973).
The mechanism by which this amnesia occurs continues to
be debated. Many theorists invoke concepts borrowed from


16
information processing models (see Detterman & Ellis, 1972;
Spear, 1978, Tulving, 1969). Christianson and Nilson (1984)
presented a list of normal faces interrupted by one grossly
deformed face. They measured skin conductance and ratings
of unpleasantness and noted that a large change in arousal
accompanied the critical event. They suggested this phasic
change in arousal interfered with acquisition of surrounding
information (i.e., an "encoding" defect affecting the
acquisition, not the retrieval, stage). Other researchers
argue against this separatist explanation and instead
contend that retrieval and encoding are interdependent
processes (e.g. Crowder, 1982, Cermak, 1982, Schacter &
Tulving, 1982).
The influence of tonic arousal on memory is more
complicated, perhaps in part because it is a more complex
multidimensional phenomenon. Tonic arousal is often
associated with the mood or state of an organism or an
overall orientation of the organism to a specific situation.
The extremes of arousal are seen when the organism is asleep
or awake. Although sometimes viewed as a unitary state,
tonic arousal is influenced by numerous factors and varies
widely across subjects and situations.
Tonic arousal can be manipulated by white noise,
increased physical activity prior to learning, or by mood
induction. It is not clear from the literature whether
these manipulations influence just physiological arousal or
both physiological and psychological aspects of arousal.


17
Many memory studies report results similar to those seen in
the phasic arousal literature, including the differences in
immediate versus delayed recall of high-arousal and low-
arousal conditions. Eysenck (1976) argues that sampling
only two points (high versus low) of the arousal continuum
may be misleading. He suggests that an inverted U shaped
relationship between immediate memory and arousal may exist,
but this cannot be demonstrated with only two points
sampled. Studies involving recall have at times yielded
conflicting results, and both semantic and phonemic
clustering have also been found to be influenced by tonic
arousal. One study demonstrated a decline in semantic
clustering in a white noise condition (Hormann & Osterkamp,
1966 as quoted in Eysenck, 1976) and Schwartz (1975)
demonstrated that white noise during learning could be used
to decrease semantic clustering in free recall, while
improving performance on phonemically related words.
Being in the same mood or arousal state at retrieval as
in acquisition has also been found to improve memory
performance in college-aged subjects (e.g. Bower, Monteiro,
& Gilligan, 1978, Clark, Milberg, & Ross, 1983). Many
theories continue to be debated, but some authors suggest
physiological arousal may play an important role. Clark,
Milberg, and Ross (1983) manipulated subjects' level of
arousal by having subjects either exercise or relax for
seven minutes, had subjects learn phrases, and then tested
them for recall in either the same or different arousal


18
State. They found that subjects consistently recalled more
information when they were tested in the same state at test
and acquisition. From this they proposed that one's state
of arousal (i.e., level of tonic arousal) is one of the many
pieces of information retained along with the stimulus
content in any learning situation, and being in the same
state provides additional cues for later accessing that
information.
Changes in Brain Physiology with Aging
Physiological and biological changes that accompany
senescence are well known and have been documented over the
last fifty years. These include a loss of total brain
weight and reductions in specific populations of neurons, an
increase in senile plaques and neurofibrillary tangles, and
changes in levels of various neurotransmitters (Brizzee,
Ordy, Knox, & Jirge, 1980; Berry, 1975). Although plaques
and tangles are generally present in normal aging, their
significance has been disputed when pathological cases are
excluded (e.g., Tomlinson, 1972). How these changes
influence memory functions remains controversial.
Cotman and Holets (1985) review the human and animal
literature on structural changes in the brain with age.
They delineate some of the problems that have plagued this
area of research and note that variable results are
frequently obtained even when researchers sample the same
brain region. Because of this, links between behavioral
changes and physiological changes must be made with caution.


19
Some researchers have documented widespread changes such as
overall decreased water content in the brain, decreased
oxygen uptake, decreased glucose utilization, and
circulatory changes, while there is some suggestion that the
cell loss that accompanies aging is probably regionally
specific (Timiras, 1988). Evidence exists for significant
cell loss in the cerebral cortex, the locus coeruleus, the
substantia nigra, the cerebellum, and the hippocampus
(Kubanis & Zornetzer, 1981). Findings of cortical and
hippocampal cell loss may be linked to the changes in both
arousal and memory seen in the elderly.
Neurotransmitters have also been suggested as important
in the study of memory. The information about the role of
acetylcholine in memory performance comes from studies such
as Drachman and Leavitt (1972), who administered
scopolamine, an acetylcholine antagonist, to a group of
healthy young adults. They found scopolamine produced
transient dose-related memory problems similar to those
found in the elderly. These effects in the young could
easily be reversed with the administration of an
acetylcholine agonist. Neurotransmitters changes associated
with aging are difficult to study, but using animal models
and indirect measuring techniques some alterations that
appear to specifically accompany aging have been discovered.
There is little evidence for changes in the overall
level of most neurotransmitters, but there has been more
evidence regarding alterations in both levels of


20
neurotransmitters and receptors in particular brain regions
(Kubanis & Zornetzer, 1981) The catecholamines have been
widely studied and some age differences have been found.
Choline acetyltransferase (CAT) is the synthesizing enzyme
for acetylcholine and is easier to study because it is much
more stable in postmortem studies than acetylcholine
(Katzman & Terry, 1983). This enzyme decreases in activity
with age, especially in the hippocampus and temporal
neocortex, two brain areas repeatedly suggested as important
in memory (Katzman & Terry, 1983).
The implication of these findings is that acetylcholine
agonists, which increase the amount of acetylcholine
available at the synapse, could be used to improve memory in
the elderly. Experimental administrations of acetylcholine
agonists, however, have failed to produce dramatic changes
in memory functioning in the elderly, suggesting that a
simple lack of acetylcholine is not a sufficient explanation
for the memory problems seen in elderly subjects (Katzman &
Terry, 1983).
Neuropsychological Mechanisms in Arousal and Memory
Brain areas typically associated with the mechanism of
arousal and attention are the reticular activating system,
the diencephalon, and hypothalamus (Pribram & McGuiness,
1975). Research on arousal and the brain stem has a long
history, with earliest studies focusing on animals and sleep
and wake cycles. The brain stem has been of interest since
as early as 1949 when Moruzzi and Magoun noted that


21
electrical stimulation of the reticular formation would
increase arousal. Additional studies have demonstrated that
animals with lesions of the reticular formation can be
momentarily aroused but are typically unable to maintain
high levels of arousal (Carlson, 1977). Nolte (1988)
describes the reticular formation as being important in many
different psychological functions, diffusely organized, and
characterized by a great deal of convergence and divergence
in patterns of connectivity.
The reticular formation has a lateral portion and a
medial portion (Nolte, 1988). The gigantocellular reticular
nucleus is located in the medial zone in the rostral
medulla. In the pons, the medial zone is divided into the
oral pontine and the caudal pontine reticular nuclei. The
raphe nuclei are in the center of the reticular formation as
it goes through the medulla, pons, and midbrain.
Projections from the reticular formation to the thalamus,
hypothalamus, and basal ganglia are believed to be important
in the regulation of consciousness. These projections
terminate in the intralaminar nuclei, which has connections
throughout the cortex. Bilateral disruption of these fibers
produces prolonged unconsciousness. The pathway to the
thalamus is believed to be especially important in
maintenance of tonic arousal.
Carlson (1977) cites evidence from two animal studies
that suggests that the forebrain, defined as the cortex,
basal ganglia, limbic system, thalamus and hypothalamus, is


22
capable of producing arousal, independent of brain stem
mechanisms. First, Genovesi, Moruzzi, Palestini, Rossi, and
Zanchetti (1956) demonstrated that when the brain stem was
lesioned gradually over time, the animals were not comatose
but showed periodic signs of arousal. Batsel (1960) is also
cited in which EEG evidence demonstrated a gradual recovery
of desynchronized activity after a single brain stem lesion
in dogs. Hypothalamic lesions have also been shown to
consistently result in lethargy and hypoactivity (Nauta &
Feirtag, 1986).
Pribram and McGuinness (1975) conclude that the
behavioral evidence from both animal and human studies
supports three "neurally distinct and separate" systems of
attention. They propose three basic attentional control
mechanisms in which arousal after input is mediated
primarily by the amygdala, activation in preparation for
response is mediated by the basal ganglia, and state that
the hippocampal circuit coordinates the two.
Pribram and McGuinness (1975) locate arousal mechanisms
in the brain stem, reticular formation as well as in the
diencephalon and into the hypothalamus, and suggest that the
amygdala and related frontal cortex are important in
attentional control of the structures implicated in basic
arousal. They note that behavioral habituation will not
occur in animals with amygdala or bifrontal damage. Humans
with bilateral amgydala lesions have been noted to exhibit a
decrease in aggressive behavior, and there may be


23
differences between animals and humans in the effect of
these lesions (Carpenter & Sutin, 1983). Dorsolateral
frontal lesions have been shown to eliminate the
visceroautonomic orienting responses (Carpenter & Sutin,
1983) .
Pribram and McGuinness (1975) argue for the existence
of reciprocal systems, one in the dorsolateral frontal
cortex and the other with opposite function in orbitofrontal
region to regulate the orienting response. The existence of
this reciprocal system is used to argue for a locus of
control, which they hypothesize to be located in the
hypothalamic region. This is supported by the results of
electrical stimulation of the hypothalamus resulting in
episodes of fighting or fleeing and lesions which disrupt
the cessation of drinking and eating behavior once
initiated.
Heilman, Watson, and Valenstein (1985) define arousal
as the "physiologic state of preparing to process a
stimuli", which they separate from motor activation which
involves preparing to act or "intention". Heilman, Watson,
and Bowers (1983) summarize evidence that the right
hemisphere may play an important role in the mediation of
activation and arousal, as well as emotional behavior.
Nauta and Feirtag (1986) summarize additional evidence
that suggests that the hypothalamus is also critical in the
mediation of emotional behavior, affect, and motivation.
Their summary includes studies in which electrical


24
stimulation of the cat's hypothalamus results in increased
agitation and aggressive behavior, while weak stimulation of
the hypothalamus appears to be experienced as extremely
pleasurable or extremely aversive depending on the site
within the hypothalamus. Its connections to the limbic
system, especially the hippocampus, are suggested as
exceedingly important in memory and the determination of
what is memorable.
Hippocampal lesions, which are known to produce
profound amnesia, also influence patterns of arousal
response. The famous H.M. is the most well-studied patient
with severe amnesia that resulted from surgery to relieve
intractable epilepsy. This surgery involved bilateral
destruction of the anterior two-thirds of the hippocampus,
the hippocampal gyrus, and the amygdala (Scoville & Milner,
1957; Penfield & Milner, 1958). Despite relatively intact
old learning and social skills, H.M. is unable to overtly
recall material if there is any significant delay between
learning and recall (Milner, Corkin, & Teuber, 1968). In
addition, H.M. shows no electrodermal response (EDR) to
shock that normal subjects find painful, and he appears
unaware of internal states such as hunger, thirst, pain, and
fatigue (Hebben, Shedlack, Eichenbaum, and Corkin, 1981).
Animal studies suggest that in animals with hippocampal
lesions, phasic EDR returns to normal more rapidly, which
may represent less processing. These animals also seem
abnormally indistractable when absorbed in performing a task


25
(Pribram & McGuinness, 1975). Stimulation of the
hippocampus in cats has been associated with facial
expression suggestive of increased attention, increased
anxiety, and bewilderment (Brodal, 1981). Just as in
humans, however, overt responses can be differentiated from
covert responses on some learning tasks. Hippocampectomized
monkeys are noted to be perceptually distractible, failing
to habituate to a distractor, while behaviorally able to
cease overt responses to the distractor (Douglas & Pribram,
1969). Pribram and McGuiness (1975) conclude that more
effortful processes are abandoned in favor of more primitive
or simple relationships that do not require central control
operations when the hippocampus has been removed from the
system.
Brain lesions believed to be associated with amnesia or
deficits in the acquisition of new information include the
temporal lobes and the hippocampus, the diencephalon, and
the frontal lobes (Squire, 1982). Deficits in immediate or
short term memory have been associated with lesions in the
parietal lobes (Kolb & Whishaw, 1985). Squire (1982) notes
that investigations of the specific pattern of memory
performance of patients with lesions in different brain
areas reveals that amnesia is not a unitary disorder, that
different brain lesions are associated with different types
of memory deficits, and that some of the behavioral deficits
seen in amnesic subjects may not to be related to the
amnesia at all. Investigations finding different rates of


26
forgetting among patients with bitemporal versus
diencephalic amnesias have led to suggestions that these
amnesias represent separate types of amnesia (Huppert &
Piercy, 1977); for one group the amnesia may be related to
storage deficits, while the other amnesia may be the result
of a disruption in retrieval abilities. Changes in memory
performance seen after frontal lobe lesions include
increased proactive interference (PI) and a lack of release
from PI, increased errors of intrusions and omissions, and
specific difficulty with memory for temporal order (Kolb &
Whisaw, 1985).
Problems demonstrating the anatomical distinctions
between different types of memory problems are inherent in
the study of brain pathology in humans, since lesions
resulting from diseases or brain insult are rarely limited
to one specific brain area. In addition, limitations in our
ability to evaluate the structural integrity of a living
human brain, despite the advances in brain-imaging
techniques, continue to make specifying an exact extent and
location of areas of pathology or lesions difficult.
Attention and activation are recognized as crucial
components in memory, and both are frequently impaired in
human brain-injured populations. In the elderly, attention
is also thought to be compromised, and Kinsbourne (1982)
suggests this is due both to diffuse neuronal depletion and
to more focalized cell loss. He suggests that neuronal
depletion throughout the cortex may effect one area


27
important in an opponent process, which will disrupt the
entire system. He contends the diffuse damage should result
in the preservation of specific functions with an overall
slowing of responses, lack of vigilance, and resistance to
changes in mental set. The disruption of opponent
processing could easily interfere with attention in general,
and focalized lesions would determine the nature of an
individual's cognitive deficits. Kinsbourne (1980) suggests
that this model best fits the deficits seen in the elderly,
who show increased variability in performance compared to
younger adults as well as a more generalized decline.
Albert and Kaplan (1980) argue for more focalized
frontal deficits in the elderly, and use comparisons with
brain-damaged patients to support this contention. Two
areas they suggest may illustrate focalized impairment are
the elderly's alteration in attention/arousal and type of
difficulties they demonstrate in visuospatial performance.
They review both the electrophysiological literature and the
cognitive psychology literature for support of the deficits
in attention, and provide a qualitative analysis of the
elderly's performance on visuospatial tasks. They note that
different measures of arousal in the elderly can suggest
either under- or over-arousal and summarize some possible
explanations for these discrepancies. For example, there
may be problems in equating physiologic measures of arousal
in young and old, since it is known that the end organs
change with age. This could result in these measures no


28
longer accurately reflecting arousal in older adults.
Alternately, they also note that it may not be absolute
arousal, but the degree of congruence of arousal between the
central nervous system and the autonomic nervous system that
may change with age. Behavioral studies cited include
studies of divided attention, studies in which subjects are
required to ignore irrelevant cues, and studies which
measure central nervous functioning while engaging in these
tasks. They argue that all these differences may be related
to changes in frontal lobe functioning.
Aging, Arousal, and Memory
Overall, the arousal, aging, and memory literature
suggests that arousal is altered with increased age and that
these alterations could be important factors in the memory
performance of aging individuals. Comparisons of memory
performance between the young and old subjects suggest that
the elderly may encode information more generally and may
have difficulties in both acquisition and retrieval of new
information (Poon, 1984). Relationships between arousal and
memory have been studied almost exclusively in the young,
and in this population phasic arousal appears to be a useful
index of depth of processing, while tonic arousal has been
suggested as a cue that can be used in retrieving
information. High levels of both item specific-phasic and
tonic arousal have also been shown to interfere with memory.
It has been hypothesized that this occurs by item specific
phasic arousal interfering with acquisition of surrounding


29
information and by increased tonic arousal decreasing deep
and increasing superficial processing. Brain areas that
have been shown to be important in both arousal and memory
appear to change with increasing age in both animal and
human studies. Both over-arousal and under-arousal theories
have been suggested as important in memory performance of
the elderly.
This relationship between arousal and older adults'
memory is probably not due simply to under- or over-arousal,
but to changes in the overall mechanism of arousal and
arousal regulation. Kubanis and Zornetzer (1981), for
example, suggest that difficulties with organization and
memory strategies may be secondary to over-arousal and
changes in homeostatic control of arousal that accompanies
aging. Research to date suggests that age differences in
phasic and/or tonic autonomic arousal may be related to age
differences in memory ability.
The nature of the memory-arousal relationship is the
focus of this study. The general hypothesis which guides
these studies is that alterations of autonomic and central
arousal may be important mediators of the declining memory
performance that accompanies aging. By manipulating item
specific phasic arousal in Experiment 1 and by manipulating
physiologic arousal in Experiment 2, four questions are
specifically addressed. First, are arousal and memory
performance related the same in the elderly as in the young
with regard to both phasic and tonic arousal? Second, do


30
the effects of arousal on memory performance in elderly
support a particular information processing model of age-
related memory decline? Third, how can this interaction be
used to help understand human memory performance at all
ages? Fourth, how do these performance differences relate
to known alterations in brain pathology that accompanies
aging?


EXPERIMENT ONE: METHODS
Induced Amnesia for Pictures
Before and After a Critical Event:
Overview and Rationale
A distinctive stimulus embedded in a group of
otherwise generic verbal or nonverbal stimuli has been shown
to interfere with retention of the stimuli surrounding the
critical event (Tulving, 1969). This critical event is
known to cause physiological arousal and this arousal, may
play a role in the concomitant interference with memory
(Erdelyi & Blumenthal, 1973). Since it is also known that
older adults tend to have smaller but longer lasting
physiological responses to novelty, this study focuses on
whether this pattern of interference is altered in an older
adult age group. Subjects were asked to remember two sets
of 25 pictures. All items were simple line drawings of
easily identifiable objects, except for the center item or
critical event in the second list, which was a photograph of
either a normal or emaciated child. If the older group's
performance was disrupted significantly more than the
younger group's by the critical event, this would support
the notion that over-arousal is a problem of some cognitive
significance for the elderly as has been suggested by
Eysenck (1977). In contrast, if the older adult's memory
31


32
performance was less disrupted, this would support the
notion of under-arousal or a more complex model of
regulation of arousal as suggested by Woodruff (1985).
Subjects
30 normal younger adults and 30 normal older adults
were recruited to participate in this study. There were 18
women and 12 men in the younger sample and 21 women and 9
men in the older sample. Older subjects were volunteers
recruited through local volunteer and senior citizen
organizations and were paid $10 for their participation.
Younger subjects either were recruited though the psychology
subject pool and received course credit for their
participation or were recruited through advertisements
asking for volunteers posted at Shands Teaching Hospital and
were paid $10 for their participation. Subjects in the
younger group were between the ages of 18 and 38
(mean=23.56, S.D.=5.78). Subjects in the older group were
between the ages of 60 and 80 (mean=69.56, S.D.=5.82). All
subjects were screened for neurological, psychiatric, and
medical disorders, as well as substance abuse problems or
medications that could alter their performance on memory
tasks via a questionnaire (see Appendix A). Subjects were
excluded if they had a history of stroke, uncontrolled
diabetes, epilepsy, drug abuse, a learning disability, or a
head injury that resulted in loss of consciousness for more
than one hour or hospitalization for concussion.


33
Younger adults reported having completed between 11 and
19 years of education (Mean=14.63, S.D.=2.22) and older
adults reported having completed between 8 and 20 years of
education (Mean=15.36, S.D.=3.36).
Materials
Materials for this experiment consisted of two lists of
24 line drawings with a "critical" 25th item placed at item
position 13. Both lists contained 24 sketches of easily
identifiable objects selected from a standardized set of
pictures assembled by Snodgrass and Vanderwart (1980) that
have been normed for name agreement, image agreement,
familiarity and visual complexity. The sketches chosen were
of the highest familiarity. Half the subjects saw List A
during Session 1 while the other half saw List B during
Session 1. All subjects saw the alternate list during
Session 2. For all subjects, during Session 1, a line
drawing of a snowman (Control Condition) was shown at
position 13. During Session 2, all subjects saw a
photograph (Critical Event) at item position 13. Half the
subjects were shown a muted color photograph of a normal
child holding a cup (Distinct Critical Event) while the
other half were shown a brightly colored photograph of an
extremely emaciated child (Disturbing Critical Event). The
two lists were presented a minimum of one week but not more
than two weeks apart.
Target and distractor items used for the recognition
test were chosen from the same pool of line drawings and


34
were balanced for familiarity. Correct recall was based on
acceptance of both dominant and nondominant names so that
subjects were not penalized for naming items differently
(e.g., plane, jet, and airplane were all equally acceptable
for line drawing of an airplane).
Subjects also were administered the Vocabulary Subtest
of the WAIS-R (Wechsler, 1981), the Center for
Epidemiological Studies Depression Scale (CES-D) (Radloff,
1977) and the State Trait Anxiety Inventory (STAI),
(Spielberger, Gorsuch, & Lushene, 1970). The WAIS-R
provided a screening measure which was used to compare the
young and old groups for differences in overall intelligence
as measured by a standardized instrument. The WAIS-R
Vocabulary subtest was chosen because it is relatively
insensitive to age differences, can be administered quickly,
and correlates highly with Full Scale IQ (Matarazzo, 1972).
The CES-D and STAI were administered to rule out increased
anxiety or depression in the older adults as an alternate
explanation for age-related differences in memory
performance. The CES-D was chosen as the measure of
depression because it has been normed on both young and old
adults and does not rely heavily on the somatic symptoms of
depression that may not indicate depression in the elderly
but may be represent normal physiologic changes that
accompany normal aging (Ensel, 1986).


35
Procedure
After passing initial screening subjects were scheduled
for an appointment. Upon arrival they were seated in a
recliner, given a brief description of what they would be
doing for the study, and then read and signed a consent
form.
Slides were presented by means of a slide projector
with an electronic shutter. Exposure duration was 500
milliseconds with a 500 millisecond inter-trial interval.
Prior to list presentation, subjects were asked to try to
remember what they were about to see, but were not warned
about the distinctive stimulus that was to be presented
during Session 2. Retention was tested with immediate free
recall and, after a thirty minute delay, free recall
followed by a yes/no recognition test. During the 30 minute
delay period the WAIS-R Vocabulary Subtest, the STAI, and
the CES-D were administered, as time allowed. Only two
older adult subjects were unable to finish these tasks
during the delay, and they completed the CES-D at the end of
the testing session. Most subjects completed these measures
and sat and talked with the examiner until a sufficient
delay period had elapsed.
Electrodes and transducers for psychophysiological
recording were also attached during the delay period,
approximately 20 minutes after the target slides were shown.
Electrodermal response (EDR) is frequently used as a measure
of phasic sympathetic arousal (e.g., Kleinsmith & Kaplan,


36
1963; Corteen, 1969) and has been suggested by Kahneman to
be correlated highly with attention and amount of effortful
processing. In this study EDR was measured to test for
differences in patterns of arousal to targets versus
distractors between the young and old. EDR was monitored by
Beckman instruments standard Ag/AgCl electrodes attached to
thenar and hypothenar eminences of the nondominant palm.
The analog signal was processed by a Coulbourn Model S71-22
Skin Conductance Module. This is a constant voltage system
which passes 0.5 volts across the palm during recording.
The analog signal was sampled and digitized every five
milliseconds by a Data Translation DT-2805 Analog to Digital
Converter (12-bit) housed within an IBM PC/XT microcomputer.
The digital signal was then processed by customized
software, yielding a EDR measure (in micromho units) every
50 milliseconds.
Following a five-minute adaptation period (Meyers &
Craighead, 1978) subjects were told the recognition portion
of the procedure would begin. They were instructed
initially, and reminded just prior to exposure, to avoid
deep breaths or movements that might alter the physiological
measurements. EDR's were averaged every second during the
presentation of each of the lists. The EDR was defined as
the difference in peak conductance from tonic to phasic, and
was calculated by subtracting the tonic mean from the phasic
peak for each picture. Positive scores thus reflect
conductance increases. Each EDR was also corrected for


37
range of individual responding as recommended by Lykken
(1972). To do this, each EDR was expressed as a proportion
of the magnitude of the subject's largest response during
the session. Using range corrected EDR corrects for
possible group differences in basic differences in phasic
arousal levels and allows a better measure of covert
processing.
Immediately after list presentation and after the
thirty minute delay subjects were asked to report all the
slides that they remembered seeing (i.e., free recall).
During the delayed recognition, 16 of the original target
items (i.e., those shown initially) were randomly
interspersed with 14 distractor items. Subjects were asked
to say "yes" if a slide had been shown before and "no" if it
had not. They were also asked to give a confidence rating,
on a scale from one to five, as to how confident they were
about their answer. A rating of "1" indicated they were not
certain and felt their answer was a "wild guess" while a
rating of "5" indicated that they were totally certain about
their answer.


EXPERIMENT 1: RESULTS
Psychometric Test Performance
On the WAIS-R Vocabulary Subtest younger adults
obtained raw scores between 25 and 66 (Mean=52.9, S.D.=8.3)
with age scaled scores between 8 and 15 (Mean=12.26,
S.D.=2.04). Older adults achieved raw scores between 27 and
67 (Mean=55.63, S.D.=9.95) with age scaled scores between 7
and 17 (Mean=12.8/ S.D.=2.64). The two groups were not
significantly different from each other in education
(t(50)=.99, p=.32), Raw Vocabulary Score (t(58)=1.14,
p=.25), or Age Scaled Vocabulary Score (t(58)=87, p=.39).
These data suggest that both the younger and older adults
tended to be of high average intelligence and represent a
highly educated sample.
Results of subjects' responses on the STAI and the CES-
D are presented in Table 1. Some researchers have suggested
that older adults tend to be more anxious than younger
adults and that this anxiety may partially account for the
differences in memory performance (Poon, 1985). The State
Scores from the STAI and CES-D were subjected to two
separate repeated measures ANOVA's. Analysis of the State
scores revealed no Age Group by Session interaction
(F=(l,57)=1.106, p=.30) or main effect for Session
38


39
(F(1,57)=.136, p=.71), and only a main effect for Age Group
(F (1,57) =7.19 p=. 0096, tv^.095). Analysis of the CES-D
showed the same pattern, again with no Group by Session
interaction (F(1,58)=1.6357, p=.2060) or main effect of
Session (F(1,58)=.0906, p=.7645), with only a main effect of
Age Group (F(l,58)=10.16, p=.0023, w2=.132). A t-test on
the Trait portion of the STAI also revealed Age Group
differences on this measure (t(58)=3.0467, p=.0035). The
differences in responses on the STAI and CES-D suggest that
the younger adults consistently rated themselves as more
anxious and more depressed both during the individual
testing sessions (State) and in general (Trait) than did the
older subjects. Neither young nor old changed their ratings
of their level of anxiety or depression appreciably between
Session 1 and Session 2.
Table 1
Anxiety and Depression Scores of
Younger and Older Adults
Session 1 Session 2
State
Trait
CES-D
State
CES-D
Young
36
40
13.7
37.1
15.1
(7.7)
(9.3)
(8.3)
(9.3)
(8.2)
Old
31.7
32.8
00

CO
31
8.0
(10.4)
(9.3)
(8.6)
(8.6)
(7.2)
In the literature, memory impairments suggested as
related to increased levels of depression include: decreased


40
acquisition and recall, increased errors of omission,
transposition errors, miss pairings, and reversals of
stimulus target words, decreased strategy use and
organization of to be remembered material, increased access
to sad memories, altered guessing strategies, and decreased
attention and reaction time (Salzman & Gutfreund, 1986).
Depressed individuals, probably because of their increased
tendency for omission errors, may also perform worse on
recall in comparison to recognition tasks (Niederehe, 1986) .
Of these deficits, the impairments that would be most
relevant to these data are the decrease in acquisition and
recall and the larger impairment in recall compared to
recognition memory. The literature also suggests that
increased anxiety is associated with lower performance on
both recall and recognition measures (Seigel & Loftus,
1978) .
Since older adults typically perform worse than younger
adults on tests of memory and it has been hypothesized that
a higher level of anxiety and depression may contribute to
these differences, the STAI and CES-D were included to
insure that the older adult sample was not significantly
more anxious or depressed than the younger adults. This was
clearly not the case and the differences seen between young
and old were not large. The CES-D scores were below all
recommended cutoffs scores suggestive of depression (Ensel,
1986) and the mean STAI scores were at approximately the
50th percentile for the younger adults and at the 40th


41
percentile for the older adults (Speilberger, 1970). This
suggests that although the differences are statistically
significant, both older and younger groups were scoring in
the normal range on both anxiety and depression measures.
The younger adults who were reporting both more
symptoms of anxiety and more symptoms of depression, were
also more likely to perform at a higher level on virtually
all memory measures. Few of the depression studies have
been completed looking at the effect of self report of
depression on memory performance with subjects within the
normal range of depression; the majority of the studies have
compared subjects within the depressed range to subjects
within the normal range on measures of depression (Johnson,
Magraro, 1987; Weingartner, 1986). West, Boatwright, and
Schleser (1984), in examining the correlation between self
report of affective status with memory performance and
ratings of memory performance, found a correlation between
self report of depression and self report of memory
problems, but found no significant relationship between
actual memory performance and self report of depression. A
modest negative correlation was found between self report of
anxiety and memory performance.
It is most probable that these difference in anxiety
and depression are due to a sampling bias secondary to
recruiting a number of younger subjects currently in school
and completing a course requirement, which could be
associated with increased stress, in contrast to recruiting


42
many older adults who were retired and volunteered to
participate in psychological studies, frequently because
they found such participation interesting. Although the age
difference is statistically significant, it is unlikely to
be practically significant in the context of this study
since these differences are likely to minimize rather than
accentuate any age differences.
List Effects
All subjects were exposed to two lists, half seeing
List A at Session 1 and half seeing List B at Session 1,
with all subjects seeing the alternate list (B or A) at
Session 2. Although these lists were both constructed from
the same pool of items and each item was assigned to one
list or the other randomly, analyses were completed before
combining the data from the two lists to insure that there
were no significant list effects. Three separate Age Group
by Session by Test ANOVA's were performed to test for
effects on overall immediate and delayed recall, overall
recognition, or percent recall of each item position. The
only significant interaction was between List and Session in
the immediate and delayed recall ANOVA (List x Session:
F(1,56)=4.24, p=.04, w2=.052; List: F(1,56)=2.16, p=.1470,
w2=.0180; Session: F(1,56)=1.52, p=.2224, ^=.0083) and
there were no main effects of List in any of the analyses.
The significant interaction between List and Session on
total recall revealed that subjects who were shown List A
first recalled an average of 1.6% more items on immediate


43
recall and .04% more items on delayed recall from Session 1
to Session 2, while subjects who saw list two first,
recalled an average of 2.3% fewer items on immediate recall
and 4.8% fewer items on delay recall. Although
statistically significant, this difference was very small
and was not practically significant within the context of
this study. Since there were no interactions between the
position effects or age group membership and list, the two
lists were combined for all subsequent analyses.
Overall Recall and Recognition Performance
Performance of Young and Old Adults on tests of recall
and recognition are presented in Table 2. Previous research
with comparisons between younger and older adults on tests
of recall and recognition have found that the older adults
tend to do less well than younger adults on tests of recall,
but tend to do as well as younger adults on tests of
recognition and decay over a delay. Table 2 reveals that
this pattern of performance was also found in this study.
A 2(Age Group) x 2(Session) x 2(Immediate vs. Delayed
Recall) Repeated Measures ANOVA with the Recall Score and
Session as the repeated measures revealed a significant
effect for Immediate versus Delayed Recall (F(1,57)=1.06,
p=.0001, w^=.781) and a significant main effect of Age Group
(F(l,57)=5.24, p=.026, w^=.067). Both young and old
recalled fewer words after a delay and older adults recalled
fewer items than the younger adult groups on both recall


tasks. There were no other significant main effects or
interactions.
44
Table 2
Performance on Recall and Recognition
Session
1
Session 2
Immediate
Recall
Delayed
Recall
Recoa-
nition
Immediate
Recall
Delayed
Recall
Recoa-
nition
Young 11.0
(2.7)
8.4
(2.9)
24.7
(2.9)
11.0
(3.3)
8.4
(2.9)
24.2
(2.8)
Old 9.8
(2.7)
7.3
(2.8)
25.5
(2.5)
9.6
(2.6)
6.5
(3.0)
24.5
(2.4)
In contrast, a 2(Age Group) by 2(Session) Repeated
Measures ANOVA on recognition scores suggested no Age by
Session interaction (F(1,58)=.39, p=.53) and no main effect
of Age Group (F(1,58)=.87, p=.35). The main effect of
Session approached significance (F(1,58)=3.86, p=.054,
w^=.045), with both younger and older adults correctly
recognizing slightly more items during Session 1.
Effect of Item Position and
the Critical Event on Memory
Because of the large number of positions, and because a
priori it was predicted that the distinctive stimulus would
primarily influence recall for the immediately surrounding


45
groups of items, recall for items was collapsed across item
positions with items 1-3 designated "Primacy" items, items
4-7, 8-11, 15-18, and 19-22 designated "Intermediate" items,
items 12-14 designated "Middle" items, and items 23-25
considered "Recency" items for Session 1. For Session 2,
items 12, 13, and 14 are considered separately in order to
test for the effect of the Critical Event. These points are
plotted for each age group in Figures 1 and 2 A
9(Position) by 2(Age Group) by 2(Session: without vs. with
critical event) repeated measures ANOVA revealed a
significant Position by Age Group by Session interaction
(Position x Age x Session: F(8,51)=2.08, p=.04, ^=.015;
Age: F(l,58)=3.44, p=.0687, w^=.0390; Session: F(1,58)=6.79,
p=.0117, w^=.087) and Session by Position interaction
(Session x Position: F(8,51)=11.94, p=.0001, ^=.152;
Position: F(8,51)=16.11, p=.0001, v^.197).
Since an a priori prediction was that the Critical
Event would effect items immediately surrounding it, Dunn's
test or a Bonferroni t test was used to determine whether
the Session 2 critical event was significantly better
remembered than Session 1 middle items, and whether Item 12
(immediately preceding the CE), and Item 14 (immediately
following the CE), were remembered less well than Session 1
center items. Since the ANOVA suggested that each age group
was affected differently, each was tested separately and p
values needed for significance were corrected for the number
of comparisons (i.e., 3 comparisons per age group). This


P o
100
p
e
r
c
e
n
t
R
e
1
1
Figure 1. Immediate Recall Performance of Younger Adults at Time 1 and
Time 2.



p
e
r
c
e
n
t
R
e
c
a
1
1
100
80
60
40
20
25
0
0
5
10 15
Item Position
20
Figure 2. Immediate Recall Performance of Older Adults at Time 1 and
Time 2.
-j


48
analysis suggested that the CE was remembered significantly
better than Session 1 middle items for both young and old
(Young: t(29)=4.0, pc.Ol; Old: t(29)=3.61, p< .01), and that
item 12 was remembered significantly less well by the
younger adults (t(29)=4.0, pc.Ol). Although the decline in
memory for item 14 approached significance for the young
adults (t(29)=1.88, p>.05), older adults' memory for items
12 and 14 was not significantly impaired (Item 12 t(29)=.53,
p>.60, Item 14 t(29)=.12; p>.90).
To avoid a loss of power and to avoid increasing
experimentwise Type I error, only center positions were
tested for age differences. However, it appears that both
younger and older adults showed similar primacy and recency
effects. Both young and old had a significant increase in
their memory for the critical item, but only the younger
adults showed a reduction in memory for items immediately
surrounding the critical item. Only the item immediately
preceding the critical item was significantly effected.
Older adults reported the CE less frequently than did the
younger adults, but this difference was not statistically
significant (t(29)=1.59, p=.ll).
To test for differences between the two different
critical events (i.e., Disturbing: starving child vs.
Distinctive: normal child photograph) an additional ANOVA
was performed. This 2(Age Group) by 2(CE Type: Disturbing
vs. Distinctive) by 3(Item Position: 12, 13, and 14) ANOVA
suggested that there were significant interactions


49
between Item Position and Age Group (Age Group x Item
Position: F(2,55)=4.48, p=.0135, w2=.033/ Age Group:
F(1,55)=.16, p=.3881, w^<.0001; Item Position: F(2,
55)=43.04, p=.0001, w^=.398) as well as between CE Item Type
and Age Group (CE Type x Age Group: F(l,56)=12.11, p=.0010,
w2=.07; CE Type: F(l,55)=.19, p=.9723, w^c.OOOl). No other
main effects or interactions were significant. The majority
of the variance in this model was accounted for by Item
Position, while Age Group and Position and Age Group and CE
Type interactions account for a statistically significant
but relatively small portion of the variance.
The immediate recall performances of the two age groups
for each of the stimuli are presented in Figures 3 and 4.
Inspection of these figures revealed that although older
adults were less likely than younger adults to remember
either critical event, the younger adults were less likely
than older adults to remember items immediately surrounding
the critical item. In addition, although the starving child
or normal child stimuli were equally likely to be remembered
by the younger subjects, the younger adults were less likely
to remember the items immediately surrounding the picture of
the starving child than the items surrounding the normal
child. Older adults had exactly the opposite pattern, being
more likely to remember the items surrounding the photograph
of the starving child. The pattern seen by the younger
adults is consistent with previous research, in which more
disturbing stimuli resulted in more pronounced amnestic


100
p
e
r
c
e
n
t
R
e
c
a
1
1
' Normal Child
Starving Child
Mean Center Items
Figure 3. Comparison of Younger Adult's Recall of the Normal and the
Starving Child and Surrounding Items.
U1
o


]
"I Normal Child
Starving Child
Mean Center Items
Figure 4. Comparison of Older Adult's Recall of the Normal and the
Starving Child and Surrounding Items. .
01


52
effects for surrounding items (Erdelyi and Blumenthal,
1972) The pattern seen by the older adults suggests that
their memory for surrounding events is not as profoundly
disturbed by distinctive stimuli, and in fact may be less
disrupted by what is more disturbing to younger adults.
Although the sample sizes are small, it is also
interesting to compare the memory performance of older
adults who did recall the critical event with older adults
who did not. Figure 5 compares the memory performance on
items 12, 13, and 14 for the 19 older adult subjects who did
recall the critical item with the 11 subjects who did not.
Although the small numbers preclude any meaningful
statistical analysis, these comparisons do not suggest that
older adults who do remember the critical item are
remarkably different from those who do not on the item
immediately preceding the critical item (t(28)=.18, p=.85).
Those who do not recall the critical event may be more
likely to recall the item immediately following the critical
item (t(28)=1.8, p=.08), although this difference is not
statistically significant.
Response Types
Although most previous studies, and this study as well,
found no difference between young and old on the overall
recognition accuracy, it has been suggested that there may
be differences in response styles and the types of errors
each Age Group is likely to make. It has been suggested


100
Recalled Cl
EH
No Recall of Cl
Mean Center Items
J
Figure 5. The Effect of Remembering the Critical Event on Older
Adult's Recall for Surrounding Items.
I
CJ


54
that older adults are more likely to make false negative
responses (i.e., saying they do not recognize a stimulus
they were exposed to), while younger adults are more likely
to make false positive responses (i.e., saying that they
recognize a stimulus they were not exposed to).
The incidence of True Positives, True Negatives, False
Positives, and False Negatives is presented in Table 3. An
Average
Table 3
Number of Each Response Type
True
True
False
False
Positives
Neaatives
Positives
Neaatives
(32 possible)
(28 possible)
(32 possible)
(28 possible)
Young 27.8
24.4
3.6
4.2
(3.0)
(2.7)
(2.7)
(3.0)
Old 26.3
26.3
1.7
5.7
(3.8)
(1.8)
(1.8)
(3.8)
examination of the response types of young and old suggests
that this may have been the case in this recognition task.
Both d' and Beta were calculated for each subject based
on the 60 responses on the recognition tasks administered at
time one and time two. The measure d' is an index of how
sensitive a subject is to a signal or target, while Beta is
an index of response bias. A higher d' indicates that a
subject needs a stronger signal or perhaps needs to be more
certain that a target has been seen before the subject will


55
endorse it as a previously exposed item. A Beta higher than
one indicates that a subject is biased towards saying "no",
that they did not see the stimulus previously, while a Beta
less than one suggests that the subject is biased towards
"yes" responses, that they did see the stimulus previously
(McNicol, 1972).
In this study, both young and old averaged Beta's
slightly greater than one, suggesting a small bias towards
caution for both young and old (Young mean Beta =1.21,
S.D.=.37, Old mean Beta=1.56, S.D.=.84). Comparisons of
these means suggested that older adults were significantly
more cautious and likely to say "no" than the younger
subjects (t(58)=4.15, p=.05). The older adults' d' was also
significantly greater than the young adults, suggesting that
older subjects had a higher response criterion and were more
accurate discriminators (Young mean d'=1.75, S.D=.80, Old
mean d'=2.19, S.D.=.84; t(58)=4.18, p=.05).
Electrodermal Response to Recognized
and Unrecognized Targets
During the recognition phase of this study,
electrodermal response (EDR) was measured, as an index of
sympathetic arousal. A 2(Age Group) x 4(Response Type: true
positives, true negatives, false positives, and false
negatives) ANOVA on the range corrected EDR was not
significant for the overall model (F(7)=1.90, p=.066) and
did not suggest an age by response type interaction or an
overall effect for age group. A separate ANOVA examining


56
the effect of Age Group and Stimulus Type (i.e., target
versus distractor) was significant (F(3,3566)=3.40, p=.017),
suggesting an overall effect of Stimulus Type
(F(1,3566)=9.08, p=.0026, w^.002), but no effect of Age
Group (F(l,l)=.17, p=.69) or interaction (F(l,l)=.96,
p=.33). These data suggest that regardless of a subject's
overt response or age group membership, they show greater
sympathetic activation to targets than to distractors. This
relationship is shown in Figure 6. However, the omega
squared value suggests that whether the stimulus is a target
or distractor accounts for only a very small proportion of
the variance in EDR.


t O H p.dfi-ott''ion
R
a
n
g
e
Figure 6. Electrodermal Response to the Different Response Types.
Ul


EXPERIMENT 1: DISCUSSION
This study examines whether exposure to an arousal
inducing Critical Event (CE) has the same effect on young
and old adults' memory for both the CE itself and the
stimuli immediately surrounding the CE.
It was found that these two age groups did not differ
significantly in education or intelligence, as measured by
the Vocabulary subtest of the WAIS-R, so it is unlikely that
differences in memory performance which did emerge could be
attributed to formal schooling or intelligence. Anxiety and
depression measures were included to insure that the older
age group was not significantly more anxious or more
depressed than the younger, since increased anxiety or
depression has been suggested as one possible explanation
for age differences found between younger and older adults.
In this sample the two groups were significantly different
in their responses on the STAI and the CES-D, but it was the
younger age group that was endorsing items suggestive of
higher levels of anxiety and depression. Since virtually
all the literature on depression and anxiety and memory
performance suggests that more anxious and depressed
subjects will do less well on memory measures, and it was
the younger adults who reported more anxiety and depression
58


and who performed better on the memory measures, it is
likely that these differences would minimize rather than
exaggerate age differences.
59
The pattern of results obtained on recognition and
recall measures, when comparing younger and older adults, is
consistent with previous research in which significant
differences are found on tests of free recall, but small or
insignificant differences are found on tests of recognition.
This supports the notion that the memory patterns seen in
this sample of young and old adults represent reliable,
replicable effects that have been demonstrated across
repeated studies.
Inspection of the effect of item position on recall
shows that, just as in previous research, both younger and
older adults show both primacy and recency effects.
However, the introduction of the CE in the middle of the
list influences the pattern of recall of young and old
differently. While younger and older adults are likely to
remember the critical event, induced retrograde amnesia
appears to be present only in the young adults. One
possible contributor to the lack of amnesia for older adults
was that, although only a trend, fewer older adults recalled
the CE. It was possible that only those older adult
subjects who failed to recall the CE would fail to show
retrograde amnesia, which could have altered the overall
pattern of recall; however, analysis of the recall patterns
of the older adults who did recall the CE compared with


60
those who did not, failed to find a difference in the effect
of the CE between these two subgroups of older adults. Even
the older adults who, like the younger adults, recalled the
CE did not show evidence of retrograde amnesia. This
suggests that item specific processing sufficient to
increase recall is not necessarily sufficient to induce
amnesia in older adults.
Additionally, young and old are affected differently by
different types of CE's. In young adults both CE' s (i.e.,
photograph of a starving child and photograph of a normal
child) resulted in equal recall of the CE, the more
disturbing CE is associated with more pronounced retrograde
and anterograde amnesia. In older adults, even though the
starving child photograph was more likely to be remembered,
there was no evidence that it resulted in a substantial
decline in recall for surrounding items.
This lack of disruption among the elderly is not easy
to explain. These data do not support the notion that older
adults are chronically over-aroused and that their memory
for items are more easily disturbed since they were, in
fact, less likely to exhibit disrupted memory than the
younger adults. It may be that the already lower memory
performance on the center items in the older adults group
may have contributed to a lack of amnesia, since there was
less of a distance for them to decline. But younger adults'
memory for the item immediately preceding the critical event
was even lower than the older adults' memory. Thus, an


61
explanation based on overall level of recall of middle items
does not seem adequate to account for this data.
How arousing stimuli affects memory performance in
older adults does appear to be clearly different from how it
affects memory performance in the young. The younger adults
seem to overfocus on the distinctive stimulus, to the
detriment of memory for surrounding items. This effect is
even more extreme when stimuli are disturbing. Older
adults, whose memory for distinctive items does not increase
as much as younger adults, do not seem to overfocus and lose
surrounding information. This difference however, does not
appear to influence overall recall, but only which items are
recalled. Since it has been suggested that manipulations in
tonic arousal influences total recall performance, the fact
that only the memory for the middle items was influenced by
the CE supports the notion that this experimental
manipulation primarily influenced phasic and not tonic
arousal.
This study also allowed us to examine response types of
younger and older adults on recognition tasks and to compare
electrodermal recognition of items. The analysis of these
results suggest different response biases and types of
errors likely with young as compared to older adults, with
younger adults more likely to have false positive responses
and older adults more accurate discriminators and being more
cautious than the young in endorsing both targets and
distractors. This response bias does not provide a


62
sufficient explanation for the item specific memory
differences found between younger and older adults, since it
was specifically the items immediately surrounding the
critical event that showed greatest differences between
young and old adults. It is possible that the older adults
tendency towards caution contributed to their reporting the
CE less frequently (although again, this difference was not
statistically significant) but cannot explain why the older
adults failed to show a decrement in memory for items
surrounding the CE.
Analysis of EDR suggested that both younger and older
adults tended to respond more strongly to targets than to
distractors, regardless of whether the target was explicitly
recognized, although target versus distractor status
accounted for a very small proportion of the variance in
EDR. No age differences or interactions were demonstrated
in this phenomenon. This suggests that in older and younger
adults, relative sympathetic arousal response to previously
exposed stimulus is an unlikely source for memory
differences. However, these measures were taken only during
the recognition portion of this study and it is noteworthy
that the overt, as well as covert, recognition failed to
demonstrate age differences as well. Differences in arousal
during acquisition or recall may still be present and
contribute to age-related memory differences.
The age differences found in reported levels of anxiety
and depression measures may also reflect the lower level of


63
arousal in older adults and may have contributed to the
different patterns of memory performance found in the two
age groups. The results may be altered with an older adult
group with higher levels of anxiety or depression, or with a
younger adult group with lower levels of anxiety and
depression. Although it is unlikely that the age
differences in anxiety and depression account for the age
differences in memory performance since both groups were
within normal limits on the measures of anxiety and
depression, additional research including samples of
subjects with more variability in tonic arousal would
clarify this issue.
It is also possible for the Yerkes-Dodson curve to
influence age differences in three different ways. First,
older and younger adults, due to cohort differences or
differences in their experience or lifetime experiences or
exposure to disturbing photographs or stimuli may be
responding differently to the photographs presented as the
critical events which could result in arousal levels being
at different points on the curve for the two age groups.
Different photographs or different types of distinctive or
disturbing events may result in arousal levels for young and
old at different places on the Yerkes-Dodson curve that has
been hypothesized to influence performance. Secondly, tonic
arousal differences between young and old may result in the
Yerkes-Dodson curve itself being different for two age
groups. Finally, there could be an interaction between the


64
age-related differences in reaction to the stimuli and the
different curves for the two age groups. It is not possible
to explore this possibility within this study since only two
levels of arousal were sampled, but additional research
sampling more points on the phasic arousal curve could show
a different relationship between arousal and aging.


EXPERIMENT 2: METHODS
The Interaction of Age and Increased
Tonic Arousal on a Suoraspan List Learning Task
Overview and Rationale
Whereas the first experiment manipulated arousal
processes associated with individual items and observed the
resulting effects on item position data, the second study
manipulated overall (tonic) levels of physiologic arousal
and evaluate its effects on general levels of recall and
recognition. Psychophysiological studies of the elderly
have been interpreted to suggest that tonically, the elderly
are both less aroused (e.g., Thompson & Nowlin, 1973) and
more highly aroused than the young (e.g., Woodruff, 1985).
While a low level of white noise and moderate exercise
increase arousal and improved delayed memory performance in
a group of college students (Eysenck, 1977), a white noise
condition has been shown to interfere with the performance
of an elderly group while exercise caused an improvement of
an elderly group's performance on another cognitive task
(Woodruff, 1985). This illustrates that arousal may not be
a single state variable, and that differences may exist
between different kinds of arousal states. Young and old
may be influenced differently by changes in state arousal.
Other studies have suggested that heightened arousal may
65


66
interfere with semantic encoding of information (Eysenck,
1976; Schwartz, 1975). Since changes in strategy use and
semantic clustering has also been suggested as a possible
source of declining memory in the elderly (Poon, 1985), this
raises the possible role of arousal as a moderating variable
in these effects.
This experiment examines the effect on memory of
activities that have been known to moderately increase or
decrease levels of physiological arousal in both young and
old adults. A modified version of the California Verbal
Learning Test (Delis et al., 1983) was used to measure
immediate and delayed recall, recognition, and semantic
clustering. An exercise and a rest condition were used to
alter physiological arousal.
This experiment was designed to provide information on
how tonic arousal interacts with encoding processes in
memory. If the older group's performance improves more with
moderate exercise than with no exercise, this may be
construed as supportive of the under-arousal hypothesis
while if the opposite pattern results that may be more
supportive of the over-arousal hypothesis. In comparison to
the younger group, if they do not improve as much or at all
under the exercise condition, this would suggest that if
under-arousal is indeed a problem, increasing physiological
arousal is not sufficient to solve it.


67
Subi ects
Subjects in this experiment were recruited and screened
as outlined in Experiment 1. Again there was a young and an
old adult group, each containing 48 subjects. The younger
group in this sample were between 18 and 38 years old
(mean=19.61, S.D.=1.70) and had completed between 13 and 16
years of eduction (mean=14.2, S.D.=1.0), while the older
group was between 60 and 80 years old (mean=69.35,
S.D.=5.66) and reported completing between 8 and 20 years of
education (mean=15.6, S.D.=3.0).
Experimental Conditions
Immediately prior to exposure to the word list, 24
subjects from each Age Group were asked to exercise for five
to seven minutes and the 24 were asked to rest for five to
seven minutes. 24 subjects in each of the Age Groups were
then asked to engage in the same activity and 24 were asked
to engage in the alternate activity immediately prior to
delayed recall. During the rest condition subjects remained
seated in a recliner. During the exercise condition
subjects walked inside Shands Teaching Hospital.
Materials and Apparatus
As in experiment 1, the STAI, CES-D, and Vocabulary
subtest of the WAIS-R were administered to test for
differences in reported anxiety or depression or general
intelligence. To measure memory performance a modified
version of the California Verbal Learning Test was
constructed. This test consisted of a 20 item word list,


68
with each item fitting into one of five categories. The
word list was read three times, instead of the standard five
times, and subjects were asked to report all items they
could recall after each presentation. After a thirty minute
delay, free recall, cued recall, and forced choice
recognition were also administered. The forced choice
recognition test consisted or 42 items, the 20 targets and
22 distractors (See Appendix B).
Since it has also been suggested that younger and older
adults may react differently to the testing situation
itself, data was also collected about subject's reactions to
the distractor tasks. In addition to collecting the
physiological measures of arousal before and after engaging
in either rest or exercise, these measures were also taken
at the beginning of the 30 minute delay, and immediately
after learning the word list in order to be compared with
these same measures after engaging in the distractor tasks.
Subjects were also asked to subjectively rate how they
were feeling on the Self Assessment Mannikin or SAM (Hodes,
Cook, & Lang, 1985). This measure asks subjects to place
themselves along a nine point continuum on three different
dimensions: a happy to sad dimension, an excited to calm
dimension, and a feeling in control to feeling out of
control dimension. These measures provide both objective
and subjective information about unintended changes in
arousal produced by participating in this study. Again,
this was used as a manipulation check and to rule out


alternate explanations for the differences seen in memory
performance between young and old.
69
Both immediately before and immediately after this five
to seven minute period blood pressure and pulse rate were
measured. These measures were taken as a check on the
experimental manipulation because they are very responsive
to increased physical activity (Clark, Milberg, & Ross,
1983). Blood pressure and heart rate were chosen because
they can be measured quickly and easily. These measures
were taken using a Dinamap Adult/Pediatric and Neonatal
Vital Signals Monitor, Model 1846 SX. This monitor
automatically provides a measure of systolic and diastolic
blood pressure and pulse rate.
Procedure
After arriving for their appointment, subjects read and
signed a consent form. Baseline blood pressure was taken
after subjects had read and discussed the consent form with
the examiner. Those assigned to the relaxation condition
sat in a chair and were then asked to relax for five to
seven minutes. Those assigned to the exercise condition
walked around the health center with the examiner for five
to seven minutes.
Immediately after the five to seven minute period blood
pressure was taken and the modified CVLT was administered.
A third blood pressure reading was taken after the modified
CVLT was administered. During the thirty minute delay
subjects were administered the Vocabulary subtest from the


70
WAIS-R, the CES-D, and the STAI. After a twenty minute
delay, a fourth blood pressure reading was taken and
subjects were again asked to either relax for five to seven
minutes or exercise for five to seven minutes. Half of the
subjects in each group engaged in the same activity as they
did originally and the other half engaged in the alternate
task. After another blood pressure reading, subjects were
asked to recall all items from the original list, first with
no cues (delayed free recall) and then with category cues
(delayed cued recall). Finally, subjects were read a list
of 42 items and asked to say "yes" if an item had been on
the list and "no" if it had not.
The following dependent measures were collected: 1) The
number of CVLT items correctly recalled after the first,
second, and third repetitions, and after a 30 minute delay.
2) The Observed Semantic Clustering Score for each of the
previously described times. Subjects were given one point
each time they recalled one word after another that was from
the same semantic category. Credit was given for a semantic
cluster only if it was the first time each of the words had
been recalled in that trial and if the word was actually a
target. 3) The Cluster Percentage Scores for each of the
above described times. This was calculated by dividing the
Observed Clustering Score by the maximum number of clusters
possible given the number of correctly recalled items on
that trial.


EXPERIMENT 2: RESULTS
Psychometric Test Performance
On the WAIS-R Vocabulary subtest younger adults
achieved an average raw score of 49.0 (S.D.=7.1) and older
adults achieved an average of 57.7 (S.D.=9.0); with mean age
scale corrected scores being in the high average range for
both younger (mean=11.7, S.D.=1.9) and older adults
(mean=13.4, S.D=2.5). On the STAI the younger group had an
average state score of 36.2 (S.D.=8.1) and an average trait
score of 37.5 (S.D.=9.9) compared to the older groups
average state score of 31.1 (S.D.=8.1) and average trait
score of 32.2 (S.D.=7.0). On the CES-D, younger adults had
an average score of 17 (S.D.=10.6), while older adults
averaged 6.7 (S.D.=6.0).
Education, WAIS-R raw and age corrected scaled scores,
State and Trait portions of the STAI, and CES-D scores were
subjected to t-tests to test for differences between age
groups on these measures. Even when reducing significance
to control for the number of comparisons, the two groups
were significantly different from each other on all these
measures. The older group were more highly educated
(t(94)=3.19, p=.0019), achieved a higher score on the WAIS-R
71


72
vocabulary subtest (raw vocabulary, (t(89)=.15, p=.0001),
and age corrected scaled score, (t(94)=3.66, p=.0004),
reported less anxiety on both state and trait anxiety
measures (state, t(94)=3.06, p=.0029, trait, t(94)=2.97,
p=.0037) and reported fewer symptoms of depression on the
CES-D (t(94)=5.82, pc.0001).
These measures, as in Experiment 1, were for the most
part included to ensure that the older adults were not less
educated, less intelligent, more anxious, or more depressed
since all those factors could contribute to lower
performance on memory measures. As reviewed in the Results
section of Experiment 1, total recall and differences
between recall and recognition have been found to be
influenced in depression, while both total recall and
recognition are thought to be influenced by anxiety. These
age differences however, are likely to have minimized rather
than exaggerated any age differences in memory performance
found in this study.
Free Recall. Cued Recall, and Recognition
The number of items recalled and recognized by the two
age groups are shown in Table 4. A 2(Age Group) by 3(Test)
ANOVA was performed on this data to determine whether the
older and younger adult samples performed similarly to
previously reported studies with largest age differences on
tests of free recall, smaller but still significant
differences on tests of cued recall, and small or no age


73
differences on tests of recognition. This analysis
suggested that this sample did indeed follow this pattern.
Table 4
Means and Standard Deviations for Recall
Performance on Modified CVLT
(20 minute delay)
Free Recall
Cued Recall
Recognition
Young
14.43
14.79
19.06
(2.5)
(2.5)
(0.9)
Old
11.72
12.96
18.45
(3.7)
(2.9)
(1.5)
Although
older adults had
lower average
scores on all
three memory measures, the ANOVA suggested a significant Age
by Test interaction (F(2,93)=10.09, p=.0003, ^=.02) and
significant main effects of Age group (F(l,94)=15.85,
p=.0001, w^=.134) and Test (F(2,188)=341.32, p=.0001,
w2=.l&). Bonferroni t-tests, correcting for the three
comparisons, revealed that younger and older adults are
significantly different on free and cued recall after a 30
minute delay (Free recall: t(83)=4.22, pc.Ol; Cued Recall:
t(94)=3.32, pc.Ol). However, the two groups did not perform
differently on the recognition task (t(82)=2.38, p>.05).
Additional analyses, using Bonferroni t-tests, showed that
while both younger and older adults improved significantly
with recognition memory tests in comparison to both free and
cued recall (all pc.Ol), only the older adults were helped


significantly by cuing (young, t(47)=1.59, p>.ll, old,
t(47)=4.79, p<.01).
74
Effects of Exercise. Rest, and Distractor
Tasks on Measures of Arousal
The average effects of exercise and rest on pulse rate,
in beats per minute, and diastolic and systolic blood
pressure, in millimeters of Mercury, are presented in Table
5. Both absolute change and percent change from baseline
are presented. These data suggest that the exercise
manipulation had its desired effect both before the learn
trials and before final recall of the list.
All three physiologic measures increased after
exercise, but tended to decrease or remain about the same
after resting for five to seven minutes. Changes for the
young and old adults are also presented separately in Table
5. These data were subjected to two separate 2(Age Group)
by 2(Activity: Exercise or Rest) by 3(Physiologic Measures)
ANOVA's for both acquisition and test conditions, first
using the absolute change scores and then using the percent
change from baseline scores.
For the both acquisition ANOVA's, using the absolute
change scores there was a significant interaction between
Age Group and Acquisition Condition only for Systolic Blood
Pressure (F=(l,95)=6.76, p=.01, w2=.Q22). Significant main
effects for activity were found on all three physiologic
measures (Pulse Rate: F(1,95)=100.14, p=.0001, ^=.5065,
Systolic Blood Pressure. F(l,95)= 151.98, p=.0001, w2=.5971,


75
Table 5
Mean Change After Rest and Exercise
Conditions
Response
Pulse Rate
: Measure
Systolic B.P.
Diastolic B.P.
Chance
Chance
Chance
Learn Condition
Exercise
+ 14.9
+21.8
+3.7
(+21%)
( + 6%)
(+17%)
Rest
+ .02
-7.3
-4.3
(+.2%)
(-6%)
(-6%)
Test Condition
Exercise
+ 14.1
+20.1
+4.1
(+20%)
(+7%)
(+17%)
Rest
-1.3
-4.9
-1.9
(-2%)
(-3%)
(-4%)
Learn Condition
Exercise
Young
+ 16.1
+ 17.5
+4.8
(+23%)
(+8%)
(+15%)
Old
+ 13.6
+26.1
+2.5
(+20%)
(+5%)
(+20%)
Rest
Young
+1.1
-5.4
-4.5
(+2%)
(-6%)
(4%)
Old
-1.1
-9.1
-4.0
(-1%)
(-6%)
(-7%)
Test Condition
Exercise
Young
+ 17.1
+ 20.2
+5.6
(+24%)
( + 9%)
(+18%)
Old
+ 11.2
+ 19.9
+2.7
(+16%)
(+4%)
(+16%)
Rest
Young
-0.1
-4.0
-2.0
(-.3%)
(-3%)
(-3%)
Old
-2.3
-5.9
-1.9
(-3%)
(-3%)
(-4%)


76
Diastolic Blood Pressure: F(l,95)= 40.65, p=.0001, w^=.2945)
but there was no main effect for Age Group (.11 < p < .58).
The analysis using the percent change scores was essentially
identical with p values of the same magnitude and omega
square values differing by less than three percent.
An identical ANOVA using the change scores from Test
Condition revealed significant main effects of Test
Condition for all three physiologic measures (Pulse Rate:
F(1,95)=157.80, p=.0001, ^=.5946, Systolic Blood Pressure,
F(1,95)= 143.59, p=.0001, ^=.6015, Diastolic Blood
Pressure: F(l,95)= 32.81, p=.0001, ^=.2458) and a main
effect of Age Group for Pulse rate (F(1,95)=10.68, p=.015,
w^= .0367) was also found. There were no significant
interactions between Test Condition and Age Group. Again,
the analysis using the percent change data was essentially
identical, with similar p values and omega squared values
that differed by less than three percent.
These analyses suggest that the exercise manipulation
significantly increased physiologic arousal, while rest did
not. The main effect of Age Group and the Interaction
between Age Group and Arousal Level were not demonstrated
consistently in the physiologic measures and accounted for a
relatively small percentage of the variance compared with
the amount of variance consistently accounted for by
exercise condition. Young and old were both affected in the
predicted directions by the exercise manipulation, but when
there was an Exercise by Age Group or main effect of Age


77
Group effect, it was the younger adults who tended to show a
greater increase in physiologic arousal.
Because it has also been suggested that older adults
find the act of engaging in psychological tests more
arousing than do younger adults, this was also investigated.
Immediately after learning the word list, the three
physiologic measures were taken and subjects were asked to
complete the Self Assessment Mannikin (SAM) to subjectively
rate their feelings on the valence, arousal, and dominance
dimensions. Change scores were calculated for the three
physiologic measures and three SAM ratings and subjected to
t-tests with Age Group as the between subjects variable.
None of the tests of the physiologic measures suggested
there were significant differences between age groups (.14 <
P < *56), and only on the valence dimension did young and
old differ significantly on SAM (t(75)=2.88, p=.0052), with
younger adults reporting they were happier than older
adults.
From pre- to post- distractor items, the average pulse
rate declined 2.4 beats per minute (bpm) for young and
declined 1.27 bpm for the older adults. Systolic blood
pressure increased an average of 2.8 millimeters of Mercury
(mmHg) for young, and decreased 0.06 (mmHg) for older
adults. Diastolic blood pressure for both young and old
changed less than one mmHg. While younger adults rated
themselves an average of 0.04 points happier, older adults
rated themselves 0.625 points less happy (on a scale of


78
nine) after engaging in the distractor tasks. On average,
both young and old adults rated themselves as approximately
0.5 points less aroused, and 0.6 (young) and 0.8 (old)
points more dominant after engaging in the distractor task.
Overall, both objectively and subjectively this data
suggests that neither young nor old seemed to be
significantly affected either physiologically or emotionally
by the distractor tasks.
Exercise Condition and Memory
The first effect of interest was whether the exercise
versus no exercise manipulation prior to acquisition
affected recall, observed clustering, or cluster percentage
differently for the young and old. A 2(Acquisition State)
by 2(Age Group) by 3(Repetition) repeated measures ANOVA,
with time as the repeated measure, suggested that there was
no Repetition by Age Group by Acquisition State interaction
(F(2,91)=.078, p=.92) and no Age Group by Acquisition State
interaction (F(l,92)=1.5, p=.22). The Repetition main
effect was significant (F(2,91)=359.96, p=.0001, w^=.79)
with all subjects increasing the number of recalled items
over time. A main effect of Age Group was also found (F(l,
92)=10.84, p=.0014, w2=.0933) with older adults consistently
recalling fewer items than younger adults.
Two additional 2(Age Group) by 2(Acquisition State) by
3(Repetition) Repeated Measures ANOVA's were conducted on
the Observed Cluster scores and Cluster Percentage Scores.
For both these analyses, there were no interactions that


79
even approached significance. Again, the Repetition main
effect was significant (Cluster Observed. F(2,91)=92.23,
p=.0001, w^=.4892, Cluster Percentage. F(2,91)=26.81,
p=.0001, w^=.2079). Both Cluster Observed and Cluster
Percentage scores increased over time.
The second effect of interest was whether a "state
dependent" learning effect had been demonstrated and whether
this effect differed between age groups. To test this, data
were reorganized and each subject's data were placed in one
of two cells depending on whether their activities before
acquisition and memory testing was the same or different.
"Same" subjects were subjects whose activities prior to list
acquisition and memory testing were either exercise or rest
(i.e., rest-rest or exercise-exercise). "Different"
subjects were those whose activities prior to learning and
memory testing were different (i.e., rest-exercise or
exercise-rest). These data are presented in Table 6.
Table 6
Encoding/Test Correspondence
Same Different
Group
Free Rcl
Cluster
Clust %
1
1 Free Rcl
Cluster
Clust %
Younger
14.75
6.95
63.09
1
| 14.13
5.21
48.79
Older
12.92
5.63
57.70
1
| 10.54
1
3.88
45.21
After being
organized
in this
way, Free
Recall,
Observed Clustering, and Cluster Percentage data were each


80
subjected to separate 2(Age Group) by 2(Learn-Recall
Correspondence) Repeated Measures ANOVA's. All three
ANOVA's had p values less than .02 for the models, but there
were no significant interactions. For both Delayed Recall
and Clustering Observed there were main effects for both Age
Group (Delayed Recall; F(l, 92)=18.99, p=.0001, w^.1502,
Cluster Observed: F(1,92)=4.05, p=.027, w^=.0379) and Learn-
Recall Correspondence (Delayed Recall: F(l,92)=5.82, p=.018,
w^=.0403, Cluster Observed: F(l,92)=8.7, p=.004, ^=.0721).
However, when Clustering Scores were corrected for the
number of items recalled in the Cluster Percentage analysis,
Age Group as main effect was not significant (F(1,92)=.99,
p=.3218, w^c.OOOl), but Learn-Recall Correspondence remained
significant (F(l,92)=8.84, p=.0038, ^=.0762). This
analysis suggests that while older adults recalled fewer
items than younger adults after a delay, both younger and
older adults tended to recall more items if they were asked
to recall the items after engaging in the same activity as
during the learn phase. Clustering appeared to be
influenced by age only when not corrected for the total
number of items recalled, but both cluster scores tended to
be higher when subjects had engaged in the same activity
immediately before learning the list and immediately before
recalling the list. This suggests both a state dependent
learning and state dependent clustering effect.


EXPERIMENT 2: DISCUSSION
Just as in Experiment 1, anxiety and depression
measures were included to ensure that older adults were not
more anxious or more depressed than younger adults, since
those conditions have been suggested to decrease memory
performance. In this sample, it was also the younger adults
whose responses suggested higher levels of both anxiety and
depression. In addition, the older adults tended to have
slightly higher levels of education and achieved higher
scores on the WAIS-R Vocabulary subtest. These differences
were not judged to be problematic in this study since these
factors would tend to minimize, rather than maximize, age
differences. Despite this, the previously described
patterns of age differences where still found (i.e., largest
age differences on tests of free recall, older adults
benefitting more from cuing than younger adults, and minimal
or no differences found on recognition tests).
Under-arousal theories of aging and memory would have
predicted that the older adults would have benefitted from
the increased arousal associated with exercising prior to
learning the word list. There also had been some
suggestions that increased arousal is associated with
81


82
decreased semantic clustering (Woods, 1975). In this study,
despite physiologic evidence of increased arousal from the
exercise, neither young nor old appeared to benefit from
either rest or exercising immediately prior to learning the
word list, but consistently showed age differences in which
older adults recalled fewer list items than did younger
adults. Both younger and older adults increased the number
of items recalled with each successive exposure to the list,
and showed increased semantic clustering with repetition.
The fact the semantic cluster percentage also increased
after each repetition suggests that this increase cannot be
attributed to increased overall recall levels, but suggests
increased list organization with increased exposure. This
increased organization after each repetition is evident with
both younger and older adults.
The discrepancy between the results of this study and
previous research may be due to differences in how arousal
was manipulated and to the degree in which the to-be-
remembered word list could be organized for later recall.
The results may be different if cortical rather than just
physiological arousal is altered since it is likely that
cortical arousal does not influence memory in the identical
way physiological arousal influences memory performance. It
is also possible that the use of semantic organization
strategies influences memory more strongly than does arousal
state and the effect of arousal could be seen if the list
was not organizable into semantic categories.


83
State dependent learning effects have been demonstrated
repeatedly with younger adults, but have not been
demonstrated previously with older adults. This study
successfully showed that, for both young and old, being in
the same general state of physiological arousal immediately
prior to acquisition and immediately prior to recalling a
list enhances not only learning, but also the amount of
semantic clustering subjects demonstrate. No age
differences or interactions were found, which is consistent
with Hess and Higgin's (1983) study in which older adults
appeared equally competent as younger adults in using
general context to enhance memory performance.
Being in the same state at recall also seems to enhance
semantic clustering for both younger and older adults. If
this was due simply to the increase in number of items
recalled, this increase should disappear in the semantic
cluster percentage (which corrects for the number recalled),
but this was not the case.


GENERAL DISCUSSION
This paper began by describing behavioral changes in
memory and arousal that have been associated with normal
aging, reviewing how memory and arousal are believed to
interact in normal young adults, reviewing the brain areas
believed to be important in memory and arousal, and
suggesting what brain changes associated with aging might
influence this interaction in older adults. Arousal is a
complex phenomenon, comprised of both the background (tonic)
activity and the phasic (stimulus linked) reaction to an
event. The two studies described above examine both phasic
and tonic arousal in an effort to determine if either or
both appear to influence memory differently in older adults.
In these studies, differences between younger and older
adults were found in how phasic (event related) arousal
influenced memory. While a distinctive stimulus was
remembered better by both younger and older adults, memory
for surrounding items was only disrupted in younger adults.
Additionally, a stimulus that was more disturbing to younger
adults and resulted in more profound amnesia (compared to
another distinctive but less disturbing stimulus) did not
affect the memory of older adults at all. Tonic arousal, or
84


85
the state of an individual, seemed to influence older and
younger adults' memories similarly, since both groups
appeared able to use correspondence between acquisition and
retrieval state as a cue to assist in recall. State
dependent learning was present in younger and older adults,
with being in the same state at learning and recall
enhancing both free recall and semantic clustering in both
age groups.
The results of these two studies do not support a
simple over-arousal theory to explain the differences in
young and old on memory tasks. Increasing arousal did not
interfere with memory performance in old adults in
Experiment 2, as one might predict if the older adults were
already over-aroused, although it is possible that even
higher levels of physiologic arousal or alterations in
cortical arousal may influence the two groups differently.
Findings from Experiment 1 would also argue against an over
arousal interpretation since fewer older adults remembered
the arousing distinctive stimulus. Secondly, memory for
surrounding items was less, not more, disturbed for older
adults compared to younger adults, despite speculation that
increased arousal plays an important role in induced amnesia
for surrounding items.
Instead, these data could be used to support an under
arousal explanation for differences between young and old in
memory performance. Although increasing physiologic arousal
also failed to enhance memory in younger adults, it is


86
possible that increasing cortical rather than physiological
arousal might enhance memory. Since it is impossible to be
certain where on the Yerkes-Dodsen curve the experimental
manipulations sampled when only two points are sampled, it
is also possible that arousal was either not increased
enough or increased too much to facilitate memory. The
lower rate of recall of the distinctive stimulus by the
older adults could be explained by the under-arousal
hypothesis or could be due to a smaller reaction to what is
distinct in the older adults. However, this age difference
was only a trend and not statistically significant. Older
adults were also more likely to recall the more disturbing
or distinctive of the two critical items, perhaps suggesting
that they needed higher arousal, compared to younger adults,
in order to remember items at the same level. The fact that
amnesia for surrounding items was not induced, may also
support the notion of lowered arousal in the older adults.
In this instance, it appears to be advantageous for older
adults to be less highly aroused than the younger adults
since their memory for surrounding items was not disturbed,
while younger adults' memories were disrupted. The older
adults lower reported symptoms of anxiety may also reflect
their lower level of tonic arousal.
There were no age differences in the ability to
autonomically discriminate between targets and distractors
in the context of the recognition task. Both younger and
older reacted more strongly to targets than to distractors


87
in a recognition task, and for both groups, responses to
targets were larger regardless of whether the subjects
overtly recalled the items. It has been suggested that this
phenomenon may be another measure of implicit memory or
memory without awareness (Bauer, 1984). Previous research
had suggested that some forms of implicit memory in young
and old adults differ (Chiarello & Hoyer, 1988); the results
of this study suggest this is an area in which young and old
do not differ. It appears that young and old are equally
able to use or ignore physiologic response to stimuli as a
cue for recall, since both patterns of response and overt
recognition were not significantly different in these two
populations.
Although it is difficult to be certain how the patterns
of behavior in this study reflect age-related brain changes,
it is possible to speculate based on the literature reviewed
previously. The amygdala was suggested as important in the
regulation of arousal related to the input of information,
while the basal ganglia is associated with differences in
levels of activation. The results of Experiment 1 may
reflect the age-related changes documented in these two
areas since conditions at input appear to influence memory
differently in the younger and older adults, and the most
likely explanation for this is differences in the amount of
activation or processing each group engages in reaction to
the two distinctive stimuli. The hippocampus is believed to
be important in the mediation of arousal and memory and in


88
determining what is memorable. It is possible that these
studies reflect different hippocampal functions being
variably affected by age. State dependent learning, which
could be considered part of the mediation of memory and
arousal function, is still intact as demonstrated in
experiment 2. Age-related hippocampal differences may be
reflected in Experiment 1 with regard to deciding whether
the CE is memorable relative to surrounding items.
Frontal areas and the orienting response may be changed
with increasing age and this change may be related to the
differences in phasic arousal effects. Changes in the
frontal areas also may be suggested if the failure of older
adults to find the distinctive stimuli as memorable is
attributable to difficulties in releasing from proactive
interference (i.e., older adults are rigidly expecting line
drawings, which would lead to problems in processing the
photograph). One possible explanation for the older adult's
failure to show the same pattern of memory performance as
younger adults in Experiment 1 is that the older subjects
found the Critical Item less distinctive and/or are
distracted from fully processing the Critical Item by the
surrounding items. Either of these explanations could be
related to the frontal lobe changes that Albert and Kaplan
(1980) suggest are at the heart of age-related cognitive
changes.
Age-related changes in the influence of phasic but not
tonic arousal on memory suggest that the previously cited


89
age-related brain changes in the hippocampus and frontal
cortex may have significant effects on how memory and
arousal interact in older adults. Lesions in the reticular
formation have been most closely associated with changes in
tonic arousal in animals, and this brain area has not been
suggested as particularly affected by aging in human autopsy
studies. The results of this study are consistent with this
since the aging process less strongly affects tonic than
phasic arousal. In these two studies age differences were
found only in how phasic arousal influences memory; this
behavioral evidence is consistent with the physiological
findings of these studies.
It is difficult to be certain which brain areas are
specifically affected by aging and how these changes
influence behavior. However, this study is consistent with
previous psychophysiological, physiological, and
psychological studies which implicate frontal lobe changes
and changes in the hippocampus as important in age-related
memory change. To help determine whether the differences
seen in this study between young and old subjects were due
to diffuse brain changes or more specific focal lesions,
such as frontal lobe lesions as suggested by Albert and
Kaplan (1980), repeating experiment one using frontal lobe
patients compared to patients with more diffuse damage, such
as closed head injury patients might be illuminating.
These results also have implications for psychological
theories that have been invoked to explain behavioral age


90
differences. Salthouse (1985) has argued that age-related
general slowing is the most parsimonious explanation for
many differences seen between young and old, including
differences in memory. However, if it is merely slowing
that changes memory, in Experiment 1 it would be predicted
that retrograde amnesia would be more profound in older
adults because they should not have completed encoding of
the previously exposed stimulus by the time the distinctive
slide was shown. It would also be predicted that older
adults would take longer to recover, increasing anterograde
amnesia. Neither of these results was seen here, suggesting
that slowing is not a sufficient explanation for these
behavioral differences.
The role of organization and semantic clustering of
information as an explanation of age differences is less
clear in this study. Although a previous study found that
increased arousal with white noise decreased semantic
clustering (Schwartz, 1975), increasing physiologic arousal
through exercise in this study did not influence the
organization of to-be-remembered material. Differences
between young and old were found in the amount of semantic
clustering, but only when the cluster scores were not
adjusted for the total number of items recalled. When
semantic cluster scores did reflect the number of items
recalled, age differences dropped out, which may call into
question whether the differences in clustering cause the
lower memory performance. In addition, although no


91
instructions to cluster were given during this study, both
young and old increased clustering over time as their recall
increased.
The similarities found in the ability of young and old
to use state as a cue during recall could be seen as
consistent with Hess' (1984) findings that older adults tend
to show more general rather than specific encoding of
information. If the state one is in is viewed as a more
general cue, and this cue was present during encoding, one
would predict no age differences in the ability to use this
information during retrieval. If the phasic changes are
conceptualized as more specific cues, this would also have
predicted greater age differences in the ability of the
older adults to use this as a cue during retrieval.
It is possible that the differences seen between young
and old in their reactions to the Critical Event may be
unique to the Critical Event stimuli chosen or the modality
chosen to test. To examine for these possibilities
additional studies using older adult groups with different
distinctive stimuli would be helpful. Since this pattern of
memory performance is easy to replicate with younger adults
despite variations in stimuli, it is unlikely that a
stimulus change will significantly alter the age differences
and it is most likely that these findings will be
replicated. Replicating this design using verbal rather
than visual stimuli to examine modality specific differences


92
could be more illuminating since modality has been shown to
be an important variable in influencing age differences.
Together, these two studies illustrate ways in which
memory is both different and stays the same across the
lifespan. Although most studies show how age-related memory
changes are detrimental to overall memory performance,
Experiment 1 provides an example of how the differences in
young and old result in the older adults not losing
information relative to younger adults. Additionally, while
a CE or distinctive stimulus and the surrounding items may
be processed differently by young and old, both young and
old appear to be equally influenced by their reaction to
targets and distractors during recognition and their ability
to use their state of arousal to assist in recall. This
argues against the notion that age-related memory
differences can be attributed solely to differences in
retrieval processes. Overall these studies suggest more
questions about the nature of aging and how it may influence
the interaction between memory and arousal than it answers.
However, it also seems to clearly show that arousal and
memory do not interact in exactly the same way in younger
and older adults and that we may be exploring an important
factor in memory and aging.


APPENDIX A: SCREENING QUESTIONNAIRE
Subject Name:
DOB: Education Completed:
1)History of head injury?(LOC?)
2)Neurological Problems? (Epilepsy, stroke, periods of
numbness or tingling or visual disturbances suggestive of
TIA)
3)Psychological problems? (Medication or counselling for
depression, psychiatric hospitalization)
4)History of learning disability?
93


Full Text
UNIVERSITY OF FLORIDA
3 1262 08554 4871


AROUSAL AND MEMORY: EFFECTS OF AGING
By
CAROL J. SCHRAMKE
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1990

ACKNOWLEDGEMENTS
This dissertation is dedicated to my maternal
grandmother, Frances Gendregske Frost, who cannot understand
why my studies are so important to me, but loves me
unconditionally nevertheless. Many thanks must go to my
husband, Carson Lane, who has moved from Michigan to Florida
and then to Oregon with few complaints and who encouraged me
and believed in me whenever I needed his support. I am also
indebted to the many older adults who were enthusiastic
about my project and my interest in aging and who braved the
horrible parking situation at Shands in order to participate
in my research. Finally, I am grateful to Beverly
Funderburk, who was my legs when I was 3,000 miles away,
making the completion of this endeavor possible.
I am also wish to acknowledge my committee members Walt
Cunningham, Jaber Gubruim, Kenneth Heilman, Michael
Robinson, Robin West, and especially Russell Bauer, my
chair, for their patience and their assistance in making
this a better research project. This research was funded,
in part, by NIMH National Research Fellowship Award Number
5F31MH09640-02.
ii

TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS iv
ABSTRACT V
BACKGROUND 1
Introduction 1
Aging and Memory 4
Aging and Arousal 10
Arousal and Memory: Interactions 13
Changes in Brain Physiology with Aging 18
Neuropsychological Mechanisms in Aging and Memory.. 20
Aging, Arousal, and Memory 28
EXPERIMENT 1: METHODS 31
Induced Amnesia for Pictures Before and After a
Critical Event: Overview and Rationale 31
Subjects 3 2
Materials 33
Procedure 35
EXPERIMENT 1: RESULTS 3 8
Psychometric Test Performance 3 8
List Effects 42
Overall Recall and Recognition Performance 4 3
Effect of Item Position and the
Critical Event on Memory 44
Response Types 52
Electrodermal Recognition of Recognized
and Unrecognized Targets 55
EXPERIMENT 1: DISCUSSION 58
EXPERIMENT 2: METHODS 65
The Interaction of Age and Increased Tonic Arousal
on a Supraspan List Learning Task: Overview and
Rationale 65
Subjects 67
iii

Experimental Conditions 67
Materials and Apparatus 67
Procedure 69
EXPERIMENT 2: RESULTS 71
Psychometric Test Performance 71
Free Recall, Cued Recall, and Recognition 72
Effects of Exercise, Rest, and Distractor Tasks
on Measures of Arousal 74
Exercise Condition and Memory 78
EXPERIMENT 2: DISCUSSION 81
GENERAL DISCUSSION 84
APPENDICES
A Screening Questionnaire 93
B Modified California Verbal Learning Test 95
REFERENCES 97
BIOGRAPHICAL SKETCH 106
iv

Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
AROUSAL AND MEMORY: EFFECTS OF AGING
By
Carol J. Schramke
August 1990
Chairman: Russell M. Bauer, Ph.D.
Major Department: Clinical and Health Psychology
These studies examine the influence of phasic and tonic
arousal on memory performance in younger and older adults.
Subjects in Experiment One were asked to learn a list of 25
simple line drawings during Session One and 24 drawings with
a unique item (i.e., the critical event) in the center
position (photograph of either a normal or starving child)
during Session Two. Previous research has demonstrated that
younger adults' memory for a critical event increases, while
memory for items surrounding the critical event is
disrupted, presumably because of phasic arousal elicited by
the distinctive item. This phenomena had not been
replicated with older adults. In this study, while both
younger and older adults demonstrated increased recall of
v

the critical event, only younger adults' recall for
surrounding stimuli was disrupted. Younger adults also
demonstrated greater disruption in memory when the
photograph was subjectively more disturbing (i.e., emaciated
rather than normal child), while older adults showed similar
memory patterns for surrounding items regardless of the
nature of the center item.
In the second study, state dependent learning was
examined by manipulating physiologic arousal. Subjects
either rested or exercised immediately prior to learning a
modified version of the California Verbal Learning Test, and
then engaged in either the same or the alternate activity
immediately prior to delayed recall. Both younger and older
adults showed clear state dependent learning effects, as
well as increased semantic clustering, when in the same
state at both acquisition and recall. Age by type of memory
test interactions were found in both studies, with age
differences on recall but not recognition tasks. No age by
arousal state interactions were suggested; young and old
were equally affected by state dependent learning, and
neither group was affected by overall level of arousal
during the learn or recall phase. Brain areas implicated as
important in explaining the age differences and similarities
found include the amygdala, frontal lobes, and hippocampus.
vi

BACKGROUND
Introduction
Neuropsychology has traditionally studied brain changes
resulting from brain injury or diseases of the brain and
attempted to provide guidelines for separating normal
variation in performance from variations induced by brain
pathology. In studying aging, neuropsychologists can
contribute by clarifying the differences and similarities in
performance between young and old and by speculating as to
what brain changes these behavioral findings suggest.
Normal aging is associated with changes in both the brain
and behavior; exploring these changes offers an opportunity
for understanding how the brain influences behavior.
This paper will focus on aging and how it influences
memory and arousal. This will be accomplished by describing
the behavioral changes that have been associated with aging
in memory and arousal, how memory and arousal are believed
to interact in normal young adults, which brain areas are
believed to be most important for memory and arousal, and
reviewing why the brain changes associated with aging may
alter this interaction. Two studies that examine how memory
performance in young and old is influenced by manipulations
1

2
in arousal are then described. Finally, the implications of
these studies for understanding the neuropsychology of
memory and aging will be discussed.
Arousal has been conceptualized, and will be discussed
herein, as an index of attention or processing and as an
index of the state of an individual. Arousal, in the
neurological literature, is often associated with cortical
desynchrony that can be measured by electroencephalography.
This activation may be linked with an alteration in
affective state. Although it has been suggested that
physical arousal and an alteration in cognitive state are
necessary for the normal experience of emotion, an
alteration in arousal is not believed to be sufficient to
induce an emotional state (Schacter & Singer, 1962, Heilman,
Watson, & Bowers, 1983).
In the psychological literature arousal has been
conceptualized in a number of different ways. For example,
Eysenck (1976) defines arousal as an elevation in body
function that is both nonspecific and noninformational. He
acknowledges that conceptually arousal can be separated into
electrocortical, autonomic, and behavioral arousal, while
arguing that it can also be treated as a unitary phenomenon
and has been so treated historically. Psychological studies
of arousal have relied on indicators such as changes in
heart rate, skin conductance response, and blood pressure to
verify alterations in activation; no studies to date have
examined what effects this alteration in physical arousal

3
has on cortical activity, except through task performance.
The physical activation resulting from exercise has been
shown to have effects on performance of many cognitive tasks
(Tomporowski & Ellis, 1986), although there is no
verification in these studies that electrocortical activity
is systematically altered.
Although increasing or decreasing different types of
arousal may produce similar performance effects, there is
sufficient evidence to argue against treating arousal as a
unitary concept. At a minimum arousal can be divided into
tonic versus phasic arousal and electrocortical versus
autonomic arousal. Electrocortical activation may also be
different if it is associated with processing rather than
orienting to a shocking or novel stimulus or if it reflects
an emotional response to a stimulus or situation.
Although these different types of arousal and how they
effect memory have been studied in young adults, patterns of
tonic and phasic arousal may change with age and could
influence memory in older adults differently than they do in
young adults. The age-related neurophysiologic changes
responsible for these alterations in arousal still need to
be determined, but also may be clarified through the study
of the behavioral differences between younger and older
adults.
Memory processes are known to change with age, and
memory studies have come to dominate psychological research
on aging (Poon, 1985). A review of the aging and memory

4
literature finds many theories about the nature of this
decline. Information-processing models, which examine
specific stages or processes necessary for memory, have been
used to examine the changes in memory of the elderly as well
as brain-injured populations. More general cognitive
functions, such as speed and one's ability to attend, are
also necessary for an individual engaging in the various
stages of information processing, and changes in these
functions may influence memory performance. Both processing
changes and alterations in attention and arousal have been
suggested as possible mechanisms to explain age-related
memory change.
Aging and Memory
Age-related alterations in memory include older adults'
general slowing, poorer performance on supraspan memory
tasks, and much worse performance on tasks requiring recall
rather than recognition when compared to younger adults
(Poon, 1985). Age differences in cross-sectional studies
can be minimized by instructing the elderly on techniques
that can improve memory (e.g., imagery) and by providing
organization of to-be-remembered material (Poon, 1985).
Most models and theories about these changes invoke
psychological or biological factors.
Psychological factors that have been suggested as
possible contributors to this decline in memory performance
include depression, anxiety, task familiarity, and levels of
motivation (Poon, 1985). An increased incidence of

5
depression among the elderly may interfere with performance
on memory tests or be related to increased memory complaints
(e.g., Niederehe & Camp, 1985; West, Boatwright, & Schleser,
1984). It also has been suggested that the elderly are less
proximally familiar with laboratory procedures or other new
learning tasks. Because of this they may analyze the tasks
differently and use a less efficient approach; or they may
view the tasks as more threatening, which could increase
their anxiety. Either of these factors could negatively
influence performance (Langer, Rodin, Beck, Weinman, &
Spitzer, 1979; Perlmutter, 1978). Although these factors
may contribute to poorer performance of the elderly on
laboratory tests of memory, Burke and Light (1981) argue
that these factors should affect all memory tasks
equivalently and they are not sufficient explanations to
account for the relatively select age differences found with
some memory tasks but not others.
In information-processing models, memory is typically
conceptualized as occurring in three stages: acquisition,
retention, and retrieval of information. Attempts to
isolate the memory difficulties associated with aging have
examined all three levels of this model. Because of the
difficultly in isolating each facet of the model, deficits
can often be explained by invoking more than one stage of
processing.
Evidence for acquisition deficits comes from studies
that show that older subjects do not spontaneously use

6
mnemonic strategies. These studies have shown that the
performance of older adults can improve, and age differences
can be minimized, when older adults are specifically
instructed to use these strategies (Rankin & Collins, 1985;
Thomas & Ruben, 1973 reported in Poon, 1984). For example,
in the Thomas and Ruben (1973) study, visual imagery
instructions, cartoon mnemonics (in which unusual
relationships between the stimulus and cue were depicted),
and a no-instruction condition were compared in a paired-
associate memory task. They found that the relatively large
differences between young and old seen under the no¬
instruction condition were greatly reduced when instructions
were provided. This suggests that older subjects benefit
more than the young when given instructions or organization
to assist in remembering.
Hess (1984) conducted two studies to examine
differences that result from manipulations at the
acquisition phase. In the first study, he presented
semantically related word pairs during the acquisition phase
(e.g., copper-iron) and during the test phase presented
either the same pair, a pair that suggested a new
interpretation of the test word (e.g., clothes-iron), or a
new context word that was similar to the original pair
(e.g., bronze-iron) in a yes/no recognition paradigm. In
the second study, word pairs were also presented but they
were all semantically unrelated. Hess found that older
adults used context information primarily when it activated

7
old learning (i.e., they did not recognize the target words
when the words were in the new context condition as well as
the younger subjects). Older subjects also had more false
positive errors for cues from the old context, making more
semantic confusion errors. This may reflect more general
and less distinctive encoding.
Results of Rabinowitz, Craik, and Ackerman's (1982)
study are also consistent with the hypothesis of less
distinctive encoding in the elderly. In this study, recall
for words to which subjects had previously generated their
own specific associates were compared to performance when
the associate or a general category cue was given during
retrieval. Older adults did not benefit as much from the
specific retrieval cues when compared with their younger
cohorts, but did equally well when provided with the more
generalized cues.
There is little evidence to support age-related
decreases in retention ability. Generally, researchers
interested in this phenomenon look for increased
interference, either proactive or retroactive, or an
increased rate of forgetting (Poon, 1985). These problems
have not been reliably demonstrated in the elderly (e.g.,
Poon and Fozard, 1980; Craik, 1977).
Proponents of a retrieval deficit theory often cite the
differences between performance on recall and recognition
tasks as supportive evidence. Young subjects do much better
on recall tests, while on recognition tasks older subjects

8
improve dramatically and the age difference in performance
levels is greatly minimized (Schonfield, 1965, Schonfield
and Robertson, 1966; Erber, 1974). It has been argued that
the older adults' ability to recognize information suggests
that the information is stored, so the problem must
therefore be one of retrieval. Poon (1985) contends it is
nearly impossible to separate retrieval problems from
acguisition difficulties, and differences between free
recall and recognition could also be explained by
inefficient encoding that would subsequently interfere with
retrieval. Poon (1985) notes that age differences can be
minimized if category cues are given at acquisition, but
these cues are not as effective when only given at the
retrieval stage. This finding leads him to argue that,
although retrieval deficits may be present, they are
probably not sufficient to account totally for the age
differences seen.
Other researchers have suggested that an age-related
slowing in performance that accompanies aging can account
for many changes in cognitive functioning, including changes
in performance on many memory tasks (e.g., Birren, 1974;
Salthouse, 1980). For example, it is noted that age
differences typically increase when time limitations are
given and are minimized when unlimited time is allowed
(Poon, 1985). Age-related slowing is noted to affect each
stage of information processing and could be responsible for
the differences seen between young and old at both

9
acquisition and retrieval (Salthouse and Somberg, 1982).
Supporters of this explanation argue that this provides one
of the most parsimonious explanations for the alterations
seen with aging, is a biologically based explanation that
should not be influenced by cohort effects, and can explain
why more complex cognitive tasks show more pronounced age
differences (Salthouse, 1985). However, although few would
argue that slowing does not influence memory performance, it
probably is not a sufficient explanation for all changes
seen in memory. Although memory differences between young
and old are typically increased when time limitations are
given, differences are maintained in many tasks even with
unlimited time. Speed explanations also have difficulty
accounting for some of the variable differences in different
types of memory tasks (Poon, 1985).
Although current findings are not conclusive, some
research suggests that part of the difference in memory
performance between young and old may be due to a difference
in response bias or response tendencies, with older adults
being more conservative. This response bias has been
demonstrated on both recall and recognition tasks, with
older adults being more likely to make errors of omission on
recall tasks and more likely to have false negative rather
than false positive errors on recognition tasks (Botwinick,
1984). Studies using signal detection analysis for
recognition of sensory stimuli have not consistently
supported the idea that older adults have a different

10
response bias (Botwinick, 1984). Memory studies, such as
Poon and Fozard's (1980) study on word recognition, have
provided some support for suggestions that older adults are
more cautious when responding in memory tasks, with older
adults in their study exhibiting a lower hit rate and
response sensitivity. The inconsistency of the research has
led some to argue that cautiousness cannot fully explain the
differences in memory performance, but differences in
response tendencies may contribute to differences in some
cases (Burke and Light, 1981).
Information processing and biological explanations for
the differences in memory performance between young and old
should not be viewed as separate from psychological and
cognitive theories. Some researchers have focused on the
patterns of cell loss to explain these deficits. This has
resulted in comparisons between normal aging and dementias,
as well as comparisons between normal aging and more focal
types of brain damage.
Aging and Arousal
Patterns of physiologic arousal are known to change
with increasing age. Woodruff (1985) and Marsh and Thompson
(1977) provide the most recent reviews of this literature.
A large number of studies have examined EEG changes and
aging. Woodruff (1985) summarizes the major findings from
these studies including changes in frequency and abundance
of alpha rhythm, changes in the incidence of beta activity,

11
diffuse slowing, focal slowing and abnormal activity in the
temporal lobes.
Autonomic nervous system changes also have been
documented. For example, changes in heart rate and
electrodermal skin conductance response that occur with
aging have frequently been used to argue for an under¬
arousal hypothesis of aging (Albert & Kaplan, 1980).
Classical conditioning studies using skin conductance
responses have shown the elderly to condition less readily
and extinguish more quickly (Botwinick & Kornetsky,
1959,1960). Older subjects also showed overall less
responsivity during the habituation period. Heart rate
deceleration in a warned reaction time procedure is believed
to be an index of filtering out irrelevant stimuli when
subjects are alert but relaxed while waiting for the
stimulus (Kahneman, 1973). In older subjects the magnitude
of the heart rate deceleration during the foreperiod is also
reduced, supporting the notion of under-arousal (Thompson &
Nowlin, 1973).
Woodruff (1985) notes, however, that many of these
studies involved passive responses to stimuli, and these
results may be quite different in situations calling for
active intentional processing. Kahneman (1973) points out
that demands on an individual's attention alters arousal,
while the level of arousal also influences how attention is
allocated. He cites the original Yerkes-Dodson studies
completed in 1908 that demonstrated that increased levels of

12
arousal improve performance on a learning task only up to a
point, and then additional arousal results in declines in
learning performance. Studies with sleep-deprived subjects,
who are considered under-aroused, typically show that
increasing motivation can improve performance to normal
levels (Kahnemen, 1973). This suggests that tonic arousal
and task demands interact to influence performance.
Others have suggested that the elderly are "over¬
aroused." Supporters of this hypothesis have relied on
biochemical measures of nervous system functioning such as
free fatty acid (FFA) in blood plasma, which is believed to
be highly correlated with the level of autonomic nervous
system activity (Woodruff, 1985). After stressful tasks the
elderly show greater FFA concentrations in comparison to
baseline measures than do the young, which led Eisdorfer,
Nowlin, and Wilkie (1970) to suggest that over-arousal
interferes with elderly performance. To test this
hypothesis they administered propranolol, an adrenergic
blocking agent, and tested an elderly population's memory
performance. They found better performance of elderly
subjects who received this drug compared with another group
who did not. However, there was no younger group with which
to compare performances, and a subsequent effort to
replicate this study using a within subjects design was
unsuccessful (Froehling, 1974) .
Studies attempting to manipulate arousal and to measure
the effects on elderly performance have produced mixed

13
results. Although not concerned with memory tasks per se,
Falk and Kline (1978) found that white noise selectively
impaired elderly performance on a critical flicker fusion
task. In contrast, Woods' (1980) study, in which body
position was used to increase arousal, found an older
group's performance was selectively enhanced on a reaction
time task. This difference may be due to the difference in
manipulations to increase arousal; arousal induced by
changes in body position may not be equivalent to change
induced by white noise.
Arousal and Memory: Interactions
Research on the interaction between arousal and memory
has a long and sometimes confusing history. Though arousal
has often been treated as a unitary phenomenon in the memory
literature, there are many important distinctions that
should be made. One of the most elementary distinctions in
arousal is the separation of event-related (phasic) arousal
from state (tonic) arousal (i.e. the overall activation
level of an organism). Phasic arousal refers to the
reaction of a organism to particular stimuli, while tonic
arousal refers to the resting (background) state of the
organism. It is also useful, within phasic arousal, to
distinguish between the arousal that indexes cognitive
processing, and the arousal that results from exposure to
highly shocking or emotional stimuli. Within tonic arousal
there may be differences in alterations induced by physical
activation, induction of mood states, and white noise.

14
Physiological arousal also may be separable from
electrocortical or central arousal.
The influence of phasic arousal on memory functions in
college students has been studied extensively, and fairly
consistent results have been obtained. Eysenck (1976,1977)
and Levonian (1972) provide reviews of this literature. In
the majority of studies the magnitude of phasic arousal at
acquisition has different effects on immediate and long-term
recall. Most studies use electrodermal skin conductance
response as the measure of phasic arousal, and find that low
arousal items are remembered best immediately but are not
recalled as well after a delay; high arousal items are not
recalled as well immediately but are recalled better after a
delay (e.g. Parkin, 1982, McLean, 1969, Levonian, 1967,
Kleinsmith & Kaplan, 1964,1963, Levinger & Clark, 1961). In
the few studies that did not produce this result, no
correction for order of presentation was instituted,
habituation to the testing situation was not achieved prior
to the start of presentation, or individual variation in
response to the stimuli was not taken into account
(Levonian, 1972).
In the earliest studies "arousal" was equated with
"emotion," and this memory pattern was interpreted as
"repression of trauma." In these studies emotional words
were used and suggested to be traumatic, but later studies
demonstrated that arousal from non-emotional stimuli could
also produce this pattern of recall (Eysenck, 1977). Most

15
recently, arousal during exposure to stimuli has been
suggested to represent the amount or depth of processing
that occurs and increased processing of arousing stimuli is
what causes the increase in delayed recall as well as
increased recognition (Pribram & McGuinness, 1975, Stelmack,
Plouffe, & Winogron, 1983). Information ultimately stored
in memory may not be as accessible immediately if the highly
arousing stimuli requires more time to be consolidated.
Other authors have focused attention on the interfering
effects of arousal on memory performance. The "von Restorff
effect" (Wallace, 1965) refers to the phenomenon in which
one novel stimulus embedded in a group of homogeneous items
is remembered better than other items (e.g. the word
"blood", embedded in a list of furniture items, will be
remembered better than the furniture items). In a variation
of this procedure Tulving (1969) demonstrated that the items
immediately preceding the novel stimulus were not remembered
as well as the other items more distant from the novel
stimulus. Tulving labeled this phenomenon "induced
retrograde amnesia" and likened it to retrograde amnesia
seen after trauma. This effect has been replicated with
both words and pictures, and it has been shown that the
amnesia can be seen for stimuli both immediately preceding
and following the novel stimuli (e.g. Saufley & Winograd,
1970, Schultz, 1971, Erdelyi & Blumenthal, 1973).
The mechanism by which this amnesia occurs continues to
be debated. Many theorists invoke concepts borrowed from

16
information processing models (see Detterman & Ellis, 1972;
Spear, 1978, Tulving, 1969). Christianson and Nilson (1984)
presented a list of normal faces interrupted by one grossly
deformed face. They measured skin conductance and ratings
of unpleasantness and noted that a large change in arousal
accompanied the critical event. They suggested this phasic
change in arousal interfered with acquisition of surrounding
information (i.e., an "encoding" defect affecting the
acquisition, not the retrieval, stage). Other researchers
argue against this separatist explanation and instead
contend that retrieval and encoding are interdependent
processes (e.g. Crowder, 1982, Cermak, 1982, Schacter &
Tulving, 1982).
The influence of tonic arousal on memory is more
complicated, perhaps in part because it is a more complex
multidimensional phenomenon. Tonic arousal is often
associated with the mood or state of an organism or an
overall orientation of the organism to a specific situation.
The extremes of arousal are seen when the organism is asleep
or awake. Although sometimes viewed as a unitary state,
tonic arousal is influenced by numerous factors and varies
widely across subjects and situations.
Tonic arousal can be manipulated by white noise,
increased physical activity prior to learning, or by mood
induction. It is not clear from the literature whether
these manipulations influence just physiological arousal or
both physiological and psychological aspects of arousal.

17
Many memory studies report results similar to those seen in
the phasic arousal literature, including the differences in
immediate versus delayed recall of high-arousal and low-
arousal conditions. Eysenck (1976) argues that sampling
only two points (high versus low) of the arousal continuum
may be misleading. He suggests that an inverted U shaped
relationship between immediate memory and arousal may exist,
but this cannot be demonstrated with only two points
sampled. Studies involving recall have at times yielded
conflicting results, and both semantic and phonemic
clustering have also been found to be influenced by tonic
arousal. One study demonstrated a decline in semantic
clustering in a white noise condition (Hormann & Osterkamp,
1966 as quoted in Eysenck, 1976) and Schwartz (1975)
demonstrated that white noise during learning could be used
to decrease semantic clustering in free recall, while
improving performance on phonemically related words.
Being in the same mood or arousal state at retrieval as
in acquisition has also been found to improve memory
performance in college-aged subjects (e.g. Bower, Monteiro,
& Gilligan, 1978, Clark, Milberg, & Ross, 1983). Many
theories continue to be debated, but some authors suggest
physiological arousal may play an important role. Clark,
Milberg, and Ross (1983) manipulated subjects' level of
arousal by having subjects either exercise or relax for
seven minutes, had subjects learn phrases, and then tested
them for recall in either the same or different arousal

18
State. They found that subjects consistently recalled more
information when they were tested in the same state at test
and acquisition. From this they proposed that one's state
of arousal (i.e., level of tonic arousal) is one of the many
pieces of information retained along with the stimulus
content in any learning situation, and being in the same
state provides additional cues for later accessing that
information.
Changes in Brain Physiology with Aging
Physiological and biological changes that accompany
senescence are well known and have been documented over the
last fifty years. These include a loss of total brain
weight and reductions in specific populations of neurons, an
increase in senile plaques and neurofibrillary tangles, and
changes in levels of various neurotransmitters (Brizzee,
Ordy, Knox, & Jirge, 1980; Berry, 1975). Although plaques
and tangles are generally present in normal aging, their
significance has been disputed when pathological cases are
excluded (e.g., Tomlinson, 1972). How these changes
influence memory functions remains controversial.
Cotman and Holets (1985) review the human and animal
literature on structural changes in the brain with age.
They delineate some of the problems that have plagued this
area of research and note that variable results are
frequently obtained even when researchers sample the same
brain region. Because of this, links between behavioral
changes and physiological changes must be made with caution.

19
Some researchers have documented widespread changes such as
overall decreased water content in the brain, decreased
oxygen uptake, decreased glucose utilization, and
circulatory changes, while there is some suggestion that the
cell loss that accompanies aging is probably regionally
specific (Timiras, 1988). Evidence exists for significant
cell loss in the cerebral cortex, the locus coeruleus, the
substantia nigra, the cerebellum, and the hippocampus
(Kubanis & Zornetzer, 1981). Findings of cortical and
hippocampal cell loss may be linked to the changes in both
arousal and memory seen in the elderly.
Neurotransmitters have also been suggested as important
in the study of memory. The information about the role of
acetylcholine in memory performance comes from studies such
as Drachman and Leavitt (1972), who administered
scopolamine, an acetylcholine antagonist, to a group of
healthy young adults. They found scopolamine produced
transient dose-related memory problems similar to those
found in the elderly. These effects in the young could
easily be reversed with the administration of an
acetylcholine agonist. Neurotransmitters changes associated
with aging are difficult to study, but using animal models
and indirect measuring techniques some alterations that
appear to specifically accompany aging have been discovered.
There is little evidence for changes in the overall
level of most neurotransmitters, but there has been more
evidence regarding alterations in both levels of

20
neurotransmitters and receptors in particular brain regions
(Kubanis & Zornetzer, 1981). The catecholamines have been
widely studied and some age differences have been found.
Choline acetyltransferase (CAT) is the synthesizing enzyme
for acetylcholine and is easier to study because it is much
more stable in postmortem studies than acetylcholine
(Katzman & Terry, 1983). This enzyme decreases in activity
with age, especially in the hippocampus and temporal
neocortex, two brain areas repeatedly suggested as important
in memory (Katzman & Terry, 1983).
The implication of these findings is that acetylcholine
agonists, which increase the amount of acetylcholine
available at the synapse, could be used to improve memory in
the elderly. Experimental administrations of acetylcholine
agonists, however, have failed to produce dramatic changes
in memory functioning in the elderly, suggesting that a
simple lack of acetylcholine is not a sufficient explanation
for the memory problems seen in elderly subjects (Katzman &
Terry, 1983).
Neuropsychological Mechanisms in Arousal and Memory
Brain areas typically associated with the mechanism of
arousal and attention are the reticular activating system,
the diencephalon, and hypothalamus (Pribram & McGuiness,
1975). Research on arousal and the brain stem has a long
history, with earliest studies focusing on animals and sleep
and wake cycles. The brain stem has been of interest since
as early as 1949 when Moruzzi and Magoun noted that

21
electrical stimulation of the reticular formation would
increase arousal. Additional studies have demonstrated that
animals with lesions of the reticular formation can be
momentarily aroused but are typically unable to maintain
high levels of arousal (Carlson, 1977). Nolte (1988)
describes the reticular formation as being important in many
different psychological functions, diffusely organized, and
characterized by a great deal of convergence and divergence
in patterns of connectivity.
The reticular formation has a lateral portion and a
medial portion (Nolte, 1988). The gigantocellular reticular
nucleus is located in the medial zone in the rostral
medulla. In the pons, the medial zone is divided into the
oral pontine and the caudal pontine reticular nuclei. The
raphe nuclei are in the center of the reticular formation as
it goes through the medulla, pons, and midbrain.
Projections from the reticular formation to the thalamus,
hypothalamus, and basal ganglia are believed to be important
in the regulation of consciousness. These projections
terminate in the intralaminar nuclei, which has connections
throughout the cortex. Bilateral disruption of these fibers
produces prolonged unconsciousness. The pathway to the
thalamus is believed to be especially important in
maintenance of tonic arousal.
Carlson (1977) cites evidence from two animal studies
that suggests that the forebrain, defined as the cortex,
basal ganglia, limbic system, thalamus and hypothalamus, is

22
capable of producing arousal, independent of brain stem
mechanisms. First, Genovesi, Moruzzi, Palestini, Rossi, and
Zanchetti (1956) demonstrated that when the brain stem was
lesioned gradually over time, the animals were not comatose
but showed periodic signs of arousal. Batsel (1960) is also
cited in which EEG evidence demonstrated a gradual recovery
of desynchronized activity after a single brain stem lesion
in dogs. Hypothalamic lesions have also been shown to
consistently result in lethargy and hypoactivity (Nauta &
Feirtag, 1986).
Pribram and McGuinness (1975) conclude that the
behavioral evidence from both animal and human studies
supports three "neurally distinct and separate" systems of
attention. They propose three basic attentional control
mechanisms in which arousal after input is mediated
primarily by the amygdala, activation in preparation for
response is mediated by the basal ganglia, and state that
the hippocampal circuit coordinates the two.
Pribram and McGuinness (1975) locate arousal mechanisms
in the brain stem, reticular formation as well as in the
diencephalon and into the hypothalamus, and suggest that the
amygdala and related frontal cortex are important in
attentional control of the structures implicated in basic
arousal. They note that behavioral habituation will not
occur in animals with amygdala or bifrontal damage. Humans
with bilateral amgydala lesions have been noted to exhibit a
decrease in aggressive behavior, and there may be

23
differences between animals and humans in the effect of
these lesions (Carpenter & Sutin, 1983). Dorsolateral
frontal lesions have been shown to eliminate the
visceroautonomic orienting responses (Carpenter & Sutin,
1983) .
Pribram and McGuinness (1975) argue for the existence
of reciprocal systems, one in the dorsolateral frontal
cortex and the other with opposite function in orbitofrontal
region to regulate the orienting response. The existence of
this reciprocal system is used to argue for a locus of
control, which they hypothesize to be located in the
hypothalamic region. This is supported by the results of
electrical stimulation of the hypothalamus resulting in
episodes of fighting or fleeing and lesions which disrupt
the cessation of drinking and eating behavior once
initiated.
Heilman, Watson, and Valenstein (1985) define arousal
as the "physiologic state of preparing to process a
stimuli", which they separate from motor activation which
involves preparing to act or "intention". Heilman, Watson,
and Bowers (1983) summarize evidence that the right
hemisphere may play an important role in the mediation of
activation and arousal, as well as emotional behavior.
Nauta and Feirtag (1986) summarize additional evidence
that suggests that the hypothalamus is also critical in the
mediation of emotional behavior, affect, and motivation.
Their summary includes studies in which electrical

24
stimulation of the cat's hypothalamus results in increased
agitation and aggressive behavior, while weak stimulation of
the hypothalamus appears to be experienced as extremely
pleasurable or extremely aversive depending on the site
within the hypothalamus. Its connections to the limbic
system, especially the hippocampus, are suggested as
exceedingly important in memory and the determination of
what is memorable.
Hippocampal lesions, which are known to produce
profound amnesia, also influence patterns of arousal
response. The famous H.M. is the most well-studied patient
with severe amnesia that resulted from surgery to relieve
intractable epilepsy. This surgery involved bilateral
destruction of the anterior two-thirds of the hippocampus,
the hippocampal gyrus, and the amygdala (Scoville & Milner,
1957; Penfield & Milner, 1958). Despite relatively intact
old learning and social skills, H.M. is unable to overtly
recall material if there is any significant delay between
learning and recall (Milner, Corkin, & Teuber, 1968). In
addition, H.M. shows no electrodermal response (EDR) to
shock that normal subjects find painful, and he appears
unaware of internal states such as hunger, thirst, pain, and
fatigue (Hebben, Shedlack, Eichenbaum, and Corkin, 1981).
Animal studies suggest that in animals with hippocampal
lesions, phasic EDR returns to normal more rapidly, which
may represent less processing. These animals also seem
abnormally indistractable when absorbed in performing a task

25
(Pribram & McGuinness, 1975). Stimulation of the
hippocampus in cats has been associated with facial
expression suggestive of increased attention, increased
anxiety, and bewilderment (Brodal, 1981). Just as in
humans, however, overt responses can be differentiated from
covert responses on some learning tasks. Hippocampectomized
monkeys are noted to be perceptually distractible, failing
to habituate to a distractor, while behaviorally able to
cease overt responses to the distractor (Douglas & Pribram,
1969). Pribram and McGuiness (1975) conclude that more
effortful processes are abandoned in favor of more primitive
or simple relationships that do not require central control
operations when the hippocampus has been removed from the
system.
Brain lesions believed to be associated with amnesia or
deficits in the acquisition of new information include the
temporal lobes and the hippocampus, the diencephalon, and
the frontal lobes (Squire, 1982). Deficits in immediate or
short term memory have been associated with lesions in the
parietal lobes (Kolb & Whishaw, 1985). Squire (1982) notes
that investigations of the specific pattern of memory
performance of patients with lesions in different brain
areas reveals that amnesia is not a unitary disorder, that
different brain lesions are associated with different types
of memory deficits, and that some of the behavioral deficits
seen in amnesic subjects may not to be related to the
amnesia at all. Investigations finding different rates of

26
forgetting among patients with bitemporal versus
diencephalic amnesias have led to suggestions that these
amnesias represent separate types of amnesia (Huppert &
Piercy, 1977); for one group the amnesia may be related to
storage deficits, while the other amnesia may be the result
of a disruption in retrieval abilities. Changes in memory
performance seen after frontal lobe lesions include
increased proactive interference (PI) and a lack of release
from PI, increased errors of intrusions and omissions, and
specific difficulty with memory for temporal order (Kolb &
Whisaw, 1985).
Problems demonstrating the anatomical distinctions
between different types of memory problems are inherent in
the study of brain pathology in humans, since lesions
resulting from diseases or brain insult are rarely limited
to one specific brain area. In addition, limitations in our
ability to evaluate the structural integrity of a living
human brain, despite the advances in brain-imaging
techniques, continue to make specifying an exact extent and
location of areas of pathology or lesions difficult.
Attention and activation are recognized as crucial
components in memory, and both are frequently impaired in
human brain-injured populations. In the elderly, attention
is also thought to be compromised, and Kinsbourne (1982)
suggests this is due both to diffuse neuronal depletion and
to more focalized cell loss. He suggests that neuronal
depletion throughout the cortex may effect one area

27
important in an opponent process, which will disrupt the
entire system. He contends the diffuse damage should result
in the preservation of specific functions with an overall
slowing of responses, lack of vigilance, and resistance to
changes in mental set. The disruption of opponent
processing could easily interfere with attention in general,
and focalized lesions would determine the nature of an
individual's cognitive deficits. Kinsbourne (1980) suggests
that this model best fits the deficits seen in the elderly,
who show increased variability in performance compared to
younger adults as well as a more generalized decline.
Albert and Kaplan (1980) argue for more focalized
frontal deficits in the elderly, and use comparisons with
brain-damaged patients to support this contention. Two
areas they suggest may illustrate focalized impairment are
the elderly's alteration in attention/arousal and type of
difficulties they demonstrate in visuospatial performance.
They review both the electrophysiological literature and the
cognitive psychology literature for support of the deficits
in attention, and provide a qualitative analysis of the
elderly's performance on visuospatial tasks. They note that
different measures of arousal in the elderly can suggest
either under- or over-arousal and summarize some possible
explanations for these discrepancies. For example, there
may be problems in equating physiologic measures of arousal
in young and old, since it is known that the end organs
change with age. This could result in these measures no

28
longer accurately reflecting arousal in older adults.
Alternately, they also note that it may not be absolute
arousal, but the degree of congruence of arousal between the
central nervous system and the autonomic nervous system that
may change with age. Behavioral studies cited include
studies of divided attention, studies in which subjects are
required to ignore irrelevant cues, and studies which
measure central nervous functioning while engaging in these
tasks. They argue that all these differences may be related
to changes in frontal lobe functioning.
Aging, Arousal, and Memory
Overall, the arousal, aging, and memory literature
suggests that arousal is altered with increased age and that
these alterations could be important factors in the memory
performance of aging individuals. Comparisons of memory
performance between the young and old subjects suggest that
the elderly may encode information more generally and may
have difficulties in both acquisition and retrieval of new
information (Poon, 1984). Relationships between arousal and
memory have been studied almost exclusively in the young,
and in this population phasic arousal appears to be a useful
index of depth of processing, while tonic arousal has been
suggested as a cue that can be used in retrieving
information. High levels of both item specific-phasic and
tonic arousal have also been shown to interfere with memory.
It has been hypothesized that this occurs by item specific
phasic arousal interfering with acquisition of surrounding

29
information and by increased tonic arousal decreasing deep
and increasing superficial processing. Brain areas that
have been shown to be important in both arousal and memory
appear to change with increasing age in both animal and
human studies. Both over-arousal and under-arousal theories
have been suggested as important in memory performance of
the elderly.
This relationship between arousal and older adults'
memory is probably not due simply to under- or over-arousal,
but to changes in the overall mechanism of arousal and
arousal regulation. Kubanis and Zornetzer (1981), for
example, suggest that difficulties with organization and
memory strategies may be secondary to over-arousal and
changes in homeostatic control of arousal that accompanies
aging. Research to date suggests that age differences in
phasic and/or tonic autonomic arousal may be related to age
differences in memory ability.
The nature of the memory-arousal relationship is the
focus of this study. The general hypothesis which guides
these studies is that alterations of autonomic and central
arousal may be important mediators of the declining memory
performance that accompanies aging. By manipulating item
specific phasic arousal in Experiment 1 and by manipulating
physiologic arousal in Experiment 2, four questions are
specifically addressed. First, are arousal and memory
performance related the same in the elderly as in the young
with regard to both phasic and tonic arousal? Second, do

30
the effects of arousal on memory performance in elderly
support a particular information processing model of age-
related memory decline? Third, how can this interaction be
used to help understand human memory performance at all
ages? Fourth, how do these performance differences relate
to known alterations in brain pathology that accompanies
aging?

EXPERIMENT ONE: METHODS
Induced Amnesia for Pictures
Before and After a Critical Event:
Overview and Rationale
A distinctive stimulus embedded in a group of
otherwise generic verbal or nonverbal stimuli has been shown
to interfere with retention of the stimuli surrounding the
critical event (Tulving, 1969). This critical event is
known to cause physiological arousal and this arousal, may
play a role in the concomitant interference with memory
(Erdelyi & Blumenthal, 1973). Since it is also known that
older adults tend to have smaller but longer lasting
physiological responses to novelty, this study focuses on
whether this pattern of interference is altered in an older
adult age group. Subjects were asked to remember two sets
of 25 pictures. All items were simple line drawings of
easily identifiable objects, except for the center item or
critical event in the second list, which was a photograph of
either a normal or emaciated child. If the older group's
performance was disrupted significantly more than the
younger group's by the critical event, this would support
the notion that over-arousal is a problem of some cognitive
significance for the elderly as has been suggested by
Eysenck (1977). In contrast, if the older adult's memory
31

32
performance was less disrupted, this would support the
notion of under-arousal or a more complex model of
regulation of arousal as suggested by Woodruff (1985).
Subjects
30 normal younger adults and 30 normal older adults
were recruited to participate in this study. There were 18
women and 12 men in the younger sample and 21 women and 9
men in the older sample. Older subjects were volunteers
recruited through local volunteer and senior citizen
organizations and were paid $10 for their participation.
Younger subjects either were recruited though the psychology
subject pool and received course credit for their
participation or were recruited through advertisements
asking for volunteers posted at Shands Teaching Hospital and
were paid $10 for their participation. Subjects in the
younger group were between the ages of 18 and 38
(mean=23.56, S.D.=5.78). Subjects in the older group were
between the ages of 60 and 80 (mean=69.56, S.D.=5.82). All
subjects were screened for neurological, psychiatric, and
medical disorders, as well as substance abuse problems or
medications that could alter their performance on memory
tasks via a questionnaire (see Appendix A). Subjects were
excluded if they had a history of stroke, uncontrolled
diabetes, epilepsy, drug abuse, a learning disability, or a
head injury that resulted in loss of consciousness for more
than one hour or hospitalization for concussion.

33
Younger adults reported having completed between 11 and
19 years of education (Mean=14.63, S.D.=2.22) and older
adults reported having completed between 8 and 20 years of
education (Mean=15.36, S.D.=3.36).
Materials
Materials for this experiment consisted of two lists of
24 line drawings with a "critical" 25th item placed at item
position 13. Both lists contained 24 sketches of easily
identifiable objects selected from a standardized set of
pictures assembled by Snodgrass and Vanderwart (1980) that
have been normed for name agreement, image agreement,
familiarity and visual complexity. The sketches chosen were
of the highest familiarity. Half the subjects saw List A
during Session 1 while the other half saw List B during
Session 1. All subjects saw the alternate list during
Session 2. For all subjects, during Session 1, a line
drawing of a snowman (Control Condition) was shown at
position 13. During Session 2, all subjects saw a
photograph (Critical Event) at item position 13. Half the
subjects were shown a muted color photograph of a normal
child holding a cup (Distinct Critical Event) while the
other half were shown a brightly colored photograph of an
extremely emaciated child (Disturbing Critical Event). The
two lists were presented a minimum of one week but not more
than two weeks apart.
Target and distractor items used for the recognition
test were chosen from the same pool of line drawings and

34
were balanced for familiarity. Correct recall was based on
acceptance of both dominant and nondominant names so that
subjects were not penalized for naming items differently
(e.g., plane, jet, and airplane were all equally acceptable
for line drawing of an airplane).
Subjects also were administered the Vocabulary Subtest
of the WAIS-R (Wechsler, 1981), the Center for
Epidemiological Studies Depression Scale (CES-D) (Radloff,
1977) , and the State Trait Anxiety Inventory (STAI),
(Spielberger, Gorsuch, & Lushene, 1970). The WAIS-R
provided a screening measure which was used to compare the
young and old groups for differences in overall intelligence
as measured by a standardized instrument. The WAIS-R
Vocabulary subtest was chosen because it is relatively
insensitive to age differences, can be administered quickly,
and correlates highly with Full Scale IQ (Matarazzo, 1972).
The CES-D and STAI were administered to rule out increased
anxiety or depression in the older adults as an alternate
explanation for age-related differences in memory
performance. The CES-D was chosen as the measure of
depression because it has been normed on both young and old
adults and does not rely heavily on the somatic symptoms of
depression that may not indicate depression in the elderly
but may be represent normal physiologic changes that
accompany normal aging (Ensel, 1986).

35
Procedure
After passing initial screening subjects were scheduled
for an appointment. Upon arrival they were seated in a
recliner, given a brief description of what they would be
doing for the study, and then read and signed a consent
form.
Slides were presented by means of a slide projector
with an electronic shutter. Exposure duration was 500
milliseconds with a 500 millisecond inter-trial interval.
Prior to list presentation, subjects were asked to try to
remember what they were about to see, but were not warned
about the distinctive stimulus that was to be presented
during Session 2. Retention was tested with immediate free
recall and, after a thirty minute delay, free recall
followed by a yes/no recognition test. During the 30 minute
delay period the WAIS-R Vocabulary Subtest, the STAI, and
the CES-D were administered, as time allowed. Only two
older adult subjects were unable to finish these tasks
during the delay, and they completed the CES-D at the end of
the testing session. Most subjects completed these measures
and sat and talked with the examiner until a sufficient
delay period had elapsed.
Electrodes and transducers for psychophysiological
recording were also attached during the delay period,
approximately 20 minutes after the target slides were shown.
Electrodermal response (EDR) is frequently used as a measure
of phasic sympathetic arousal (e.g., Kleinsmith & Kaplan,

36
1963; Corteen, 1969) and has been suggested by Kahneman to
be correlated highly with attention and amount of effortful
processing. In this study EDR was measured to test for
differences in patterns of arousal to targets versus
distractors between the young and old. EDR was monitored by
Beckman instruments standard Ag/AgCl electrodes attached to
thenar and hypothenar eminences of the nondominant palm.
The analog signal was processed by a Coulbourn Model S71-22
Skin Conductance Module. This is a constant voltage system
which passes 0.5 volts across the palm during recording.
The analog signal was sampled and digitized every five
milliseconds by a Data Translation DT-2805 Analog to Digital
Converter (12-bit) housed within an IBM PC/XT microcomputer.
The digital signal was then processed by customized
software, yielding a EDR measure (in micromho units) every
50 milliseconds.
Following a five-minute adaptation period (Meyers &
Craighead, 1978) subjects were told the recognition portion
of the procedure would begin. They were instructed
initially, and reminded just prior to exposure, to avoid
deep breaths or movements that might alter the physiological
measurements. EDR's were averaged every second during the
presentation of each of the lists. The EDR was defined as
the difference in peak conductance from tonic to phasic, and
was calculated by subtracting the tonic mean from the phasic
peak for each picture. Positive scores thus reflect
conductance increases. Each EDR was also corrected for

37
range of individual responding as recommended by Lykken
(1972). To do this, each EDR was expressed as a proportion
of the magnitude of the subject's largest response during
the session. Using range corrected EDR corrects for
possible group differences in basic differences in phasic
arousal levels and allows a better measure of covert
processing.
Immediately after list presentation and after the
thirty minute delay subjects were asked to report all the
slides that they remembered seeing (i.e., free recall).
During the delayed recognition, 16 of the original target
items (i.e., those shown initially) were randomly
interspersed with 14 distractor items. Subjects were asked
to say "yes" if a slide had been shown before and "no" if it
had not. They were also asked to give a confidence rating,
on a scale from one to five, as to how confident they were
about their answer. A rating of "1" indicated they were not
certain and felt their answer was a "wild guess" while a
rating of "5" indicated that they were totally certain about
their answer.

EXPERIMENT 1: RESULTS
Psychometric Test Performance
On the WAIS-R Vocabulary Subtest younger adults
obtained raw scores between 25 and 66 (Mean=52.9, S.D.=8.3)
with age scaled scores between 8 and 15 (Mean=12.26,
S.D.=2.04). Older adults achieved raw scores between 27 and
67 (Mean=55.63, S.D.=9.95) with age scaled scores between 7
and 17 (Mean=12.8/ S.D.=2.64). The two groups were not
significantly different from each other in education
(t(50)=.99, p=.32), Raw Vocabulary Score (t(58)=1.14,
p=.25), or Age Scaled Vocabulary Score (t(58)=87, p=.39).
These data suggest that both the younger and older adults
tended to be of high average intelligence and represent a
highly educated sample.
Results of subjects' responses on the STAI and the CES-
D are presented in Table 1. Some researchers have suggested
that older adults tend to be more anxious than younger
adults and that this anxiety may partially account for the
differences in memory performance (Poon, 1985). The State
Scores from the STAI and CES-D were subjected to two
separate repeated measures ANOVA's. Analysis of the State
scores revealed no Age Group by Session interaction
(F=(l,57)=1.106, p=.30) or main effect for Session
38

39
(F(1,57)=.136, p=.71), and only a main effect for Age Group
(F (1,57) =7.19 , p=. 0096, tv^.095). Analysis of the CES-D
showed the same pattern, again with no Group by Session
interaction (F(1,58)=1.6357, p=.2060) or main effect of
Session (F(1,58)=.0906, p=.7645), with only a main effect of
Age Group (F(l,58)=10.16, p=.0023, ^=.132). A t-test on
the Trait portion of the STAI also revealed Age Group
differences on this measure (t(58)=3.0467, p=.0035). The
differences in responses on the STAI and CES-D suggest that
the younger adults consistently rated themselves as more
anxious and more depressed both during the individual
testing sessions (State) and in general (Trait) than did the
older subjects. Neither young nor old changed their ratings
of their level of anxiety or depression appreciably between
Session 1 and Session 2.
Table 1
Anxiety and Depression Scores of
Younger and Older Adults
Session 1 Session 2
State
Trait
CES-D
State
CES-D
Young
36
40
13.7
37.1
15.1
(7.7)
(9.3)
(8.3)
(9.3)
(8.2)
Old
31.7
32.8
00
•
CO
31
8.0
(10.4)
(9.3)
(8.6)
(8.6)
(7.2)
In the literature, memory impairments suggested as
related to increased levels of depression include: decreased

40
acquisition and recall, increased errors of omission,
transposition errors, miss pairings, and reversals of
stimulus target words, decreased strategy use and
organization of to be remembered material, increased access
to sad memories, altered guessing strategies, and decreased
attention and reaction time (Salzman & Gutfreund, 1986).
Depressed individuals, probably because of their increased
tendency for omission errors, may also perform worse on
recall in comparison to recognition tasks (Niederehe, 1986) .
Of these deficits, the impairments that would be most
relevant to these data are the decrease in acquisition and
recall and the larger impairment in recall compared to
recognition memory. The literature also suggests that
increased anxiety is associated with lower performance on
both recall and recognition measures (Seigel & Loftus,
1978) .
Since older adults typically perform worse than younger
adults on tests of memory and it has been hypothesized that
a higher level of anxiety and depression may contribute to
these differences, the STAI and CES-D were included to
insure that the older adult sample was not significantly
more anxious or depressed than the younger adults. This was
clearly not the case and the differences seen between young
and old were not large. The CES-D scores were below all
recommended cutoffs scores suggestive of depression (Ensel,
1986) and the mean STAI scores were at approximately the
50th percentile for the younger adults and at the 40th

41
percentile for the older adults (Speilberger, 1970). This
suggests that although the differences are statistically
significant, both older and younger groups were scoring in
the normal range on both anxiety and depression measures.
The younger adults who were reporting both more
symptoms of anxiety and more symptoms of depression, were
also more likely to perform at a higher level on virtually
all memory measures. Few of the depression studies have
been completed looking at the effect of self report of
depression on memory performance with subjects within the
normal range of depression; the majority of the studies have
compared subjects within the depressed range to subjects
within the normal range on measures of depression (Johnson,
Magraro, 1987; Weingartner, 1986). West, Boatwright, and
Schleser (1984), in examining the correlation between self
report of affective status with memory performance and
ratings of memory performance, found a correlation between
self report of depression and self report of memory
problems, but found no significant relationship between
actual memory performance and self report of depression. A
modest negative correlation was found between self report of
anxiety and memory performance.
It is most probable that these difference in anxiety
and depression are due to a sampling bias secondary to
recruiting a number of younger subjects currently in school
and completing a course requirement, which could be
associated with increased stress, in contrast to recruiting

42
many older adults who were retired and volunteered to
participate in psychological studies, frequently because
they found such participation interesting. Although the age
difference is statistically significant, it is unlikely to
be practically significant in the context of this study
since these differences are likely to minimize rather than
accentuate any age differences.
List Effects
All subjects were exposed to two lists, half seeing
List A at Session 1 and half seeing List B at Session 1,
with all subjects seeing the alternate list (B or A) at
Session 2. Although these lists were both constructed from
the same pool of items and each item was assigned to one
list or the other randomly, analyses were completed before
combining the data from the two lists to insure that there
were no significant list effects. Three separate Age Group
by Session by Test ANOVA's were performed to test for
effects on overall immediate and delayed recall, overall
recognition, or percent recall of each item position. The
only significant interaction was between List and Session in
the immediate and delayed recall ANOVA (List x Session:
F (1,56) =4.24 , p=. 04 , ^=.052; List: F (1,56) =2.16, p=.1470,
w2=.0180; Session: F(1,56)=1.52, p=.2224, ^=.0083) and
there were no main effects of List in any of the analyses.
The significant interaction between List and Session on
total recall revealed that subjects who were shown List A
first recalled an average of 1.6% more items on immediate

43
recall and .04% more items on delayed recall from Session 1
to Session 2, while subjects who saw list two first,
recalled an average of 2.3% fewer items on immediate recall
and 4.8% fewer items on delay recall. Although
statistically significant, this difference was very small
and was not practically significant within the context of
this study. Since there were no interactions between the
position effects or age group membership and list, the two
lists were combined for all subsequent analyses.
Overall Recall and Recognition Performance
Performance of Young and Old Adults on tests of recall
and recognition are presented in Table 2. Previous research
with comparisons between younger and older adults on tests
of recall and recognition have found that the older adults
tend to do less well than younger adults on tests of recall,
but tend to do as well as younger adults on tests of
recognition and decay over a delay. Table 2 reveals that
this pattern of performance was also found in this study.
A 2(Age Group) x 2(Session) x 2(Immediate vs. Delayed
Recall) Repeated Measures ANOVA with the Recall Score and
Session as the repeated measures revealed a significant
effect for Immediate versus Delayed Recall (F(1,57)=1.06,
p=.0001, w^=.781) and a significant main effect of Age Group
(F(l,57)=5.24, p=.026, w^=.067). Both young and old
recalled fewer words after a delay and older adults recalled
fewer items than the younger adult groups on both recall

tasks. There were no other significant main effects or
interactions.
44
Table 2
Performance on Recall and Recognition
Session
1
Session 2
Immediate
Recall
Delayed
Recall
Recoa-
nition
Immediate
Recall
Delayed
Recall
Recoa-
nition
Young 11.0
(2.7)
8.4
(2.9)
24.7
(2.9)
11.0
(3.3)
8.4
(2.9)
24.2
(2.8)
Old 9.8
(2.7)
7.3
(2.8)
25.5
(2.5)
9.6
(2.6)
6.5
(3.0)
24.5
(2.4)
In contrast, a 2(Age Group) by 2(Session) Repeated
Measures ANOVA on recognition scores suggested no Age by
Session interaction (F(1,58)=.39, p=.53) and no main effect
of Age Group (F(1,58)=.87, p=.35). The main effect of
Session approached significance (F(1,58)=3.86, p=.054,
w^=.045), with both younger and older adults correctly
recognizing slightly more items during Session 1.
Effect of Item Position and
the Critical Event on Memory
Because of the large number of positions, and because a
priori it was predicted that the distinctive stimulus would
primarily influence recall for the immediately surrounding

45
groups of items, recall for items was collapsed across item
positions with items 1-3 designated "Primacy" items, items
4-7, 8-11, 15-18, and 19-22 designated "Intermediate" items,
items 12-14 designated "Middle" items, and items 23-25
considered "Recency" items for Session 1. For Session 2,
items 12, 13, and 14 are considered separately in order to
test for the effect of the Critical Event. These points are
plotted for each age group in Figures 1 and 2 . A
9(Position) by 2(Age Group) by 2(Session: without vs. with
critical event) repeated measures ANOVA revealed a
significant Position by Age Group by Session interaction
(Position x Age x Session: F(8,51)=2.08, p=.04, ^=.015;
Age: F(l,58)=3.44, p=.0687, w^=.0390; Session: F(1,58)=6.79,
p=.0117, w^=.087) and Session by Position interaction
(Session x Position: F(8,51)=11.94, p=.0001, ^=.152;
Position: F(8,51)=16.11, p=.0001, v^.197).
Since an a priori prediction was that the Critical
Event would effect items immediately surrounding it, Dunn's
test or a Bonferroni t test was used to determine whether
the Session 2 critical event was significantly better
remembered than Session 1 middle items, and whether Item 12
(immediately preceding the CE), and Item 14 (immediately
following the CE), were remembered less well than Session 1
center items. Since the ANOVA suggested that each age group
was affected differently, each was tested separately and p
values needed for significance were corrected for the number
of comparisons (i.e., 3 comparisons per age group). This

P o
100
p
e
r
c
e
n
t
R
e
1
1
Figure 1. Immediate Recall Performance of Younger Adults at Time 1 and
Time 2.
CTi

p
e
r
c
e
n
t
R
e
c
a
1
1
100
80
60
40
20
25
0
0
5
10 15
Item Position
20
Figure 2. Immediate Recall Performance of Older Adults at Time 1 and
Time 2.

48
analysis suggested that the CE was remembered significantly
better than Session 1 middle items for both young and old
(Young: t(29)=4.0, pc.Ol; Old: t(29)=3.61, p< .01), and that
item 12 was remembered significantly less well by the
younger adults (t(29)=4.0, pc.Ol). Although the decline in
memory for item 14 approached significance for the young
adults (t(29)=1.88, p>.05), older adults' memory for items
12 and 14 was not significantly impaired (Item 12 t(29)=.53,
p>.60, Item 14 t(29)=.12; p>.90).
To avoid a loss of power and to avoid increasing
experimentwise Type I error, only center positions were
tested for age differences. However, it appears that both
younger and older adults showed similar primacy and recency
effects. Both young and old had a significant increase in
their memory for the critical item, but only the younger
adults showed a reduction in memory for items immediately
surrounding the critical item. Only the item immediately
preceding the critical item was significantly effected.
Older adults reported the CE less frequently than did the
younger adults, but this difference was not statistically
significant (t(29)=1.59, p=.ll).
To test for differences between the two different
critical events (i.e., Disturbing: starving child vs.
Distinctive: normal child photograph) an additional ANOVA
was performed. This 2(Age Group) by 2(CE Type: Disturbing
vs. Distinctive) by 3(Item Position: 12, 13, and 14) ANOVA
suggested that there were significant interactions

49
between Item Position and Age Group (Age Group x Item
Position: F(2,55)=4.48, p=.0135, ^=.033, Age Group:
F(1,55)=.16, p=.3881, w^<.0001; Item Position: F(2,
55)=43.04, p=.0001, w^=.398) as well as between CE Item Type
and Age Group (CE Type x Age Group: F(l,56)=12.11, p=.0010,
w2=.07; CE Type: F(l,55)=.19, p=.9723, w^c.OOOl). No other
main effects or interactions were significant. The majority
of the variance in this model was accounted for by Item
Position, while Age Group and Position and Age Group and CE
Type interactions account for a statistically significant
but relatively small portion of the variance.
The immediate recall performances of the two age groups
for each of the stimuli are presented in Figures 3 and 4.
Inspection of these figures revealed that although older
adults were less likely than younger adults to remember
either critical event, the younger adults were less likely
than older adults to remember items immediately surrounding
the critical item. In addition, although the starving child
or normal child stimuli were equally likely to be remembered
by the younger subjects, the younger adults were less likely
to remember the items immediately surrounding the picture of
the starving child than the items surrounding the normal
child. Older adults had exactly the opposite pattern, being
more likely to remember the items surrounding the photograph
of the starving child. The pattern seen by the younger
adults is consistent with previous research, in which more
disturbing stimuli resulted in more pronounced amnestic

100
p
e
r
c
e
n
t
R
e
c
a
1
1
Figure 3. Comparison of Younger Adult's Recall of the Normal and the
Starving Child and Surrounding Items.
U1
o

100
80
60
40
12 13 14
Item Position
]
Normal Child
Starving Child
Mean Center Items
ai
Figure 4. Comparison of Older Adult's Recall of the Normal and the
Starving Child and Surrounding Items. .

52
effects for surrounding items (Erdelyi and Blumenthal,
1972) . The pattern seen by the older adults suggests that
their memory for surrounding events is not as profoundly
disturbed by distinctive stimuli, and in fact may be less
disrupted by what is more disturbing to younger adults.
Although the sample sizes are small, it is also
interesting to compare the memory performance of older
adults who did recall the critical event with older adults
who did not. Figure 5 compares the memory performance on
items 12, 13, and 14 for the 19 older adult subjects who did
recall the critical item with the 11 subjects who did not.
Although the small numbers preclude any meaningful
statistical analysis, these comparisons do not suggest that
older adults who do remember the critical item are
remarkably different from those who do not on the item
immediately preceding the critical item (t(28)=.18, p=.85).
Those who do not recall the critical event may be more
likely to recall the item immediately following the critical
item (t(28)=1.8, p=.08), although this difference is not
statistically significant.
Response Types
Although most previous studies, and this study as well,
found no difference between young and old on the overall
recognition accuracy, it has been suggested that there may
be differences in response styles and the types of errors
each Age Group is likely to make. It has been suggested

100
Recalled Cl
wm
No Recall of Cl
Mean Center Items
J
Figure 5. The Effect of Remembering the Critical Event on Older
Adult's Recall for Surrounding Items.
Ü1
CO

54
that older adults are more likely to make false negative
responses (i.e., saying they do not recognize a stimulus
they were exposed to), while younger adults are more likely
to make false positive responses (i.e., saying that they
recognize a stimulus they were not exposed to).
The incidence of True Positives, True Negatives, False
Positives, and False Negatives is presented in Table 3. An
Average
Table 3
Number of Each Response Type
True
True
False
False
Positives
Neaatives
Positives
Neaatives
(32 possible)
(28 possible)
(32 possible)
(28 possible)
Young 27.8
24.4
3.6
4.2
(3.0)
(2.7)
(2.7)
(3.0)
Old 26.3
26.3
1.7
5.7
(3.8)
(1.8)
(1.8)
(3.8)
examination of the response types of young and old suggests
that this may have been the case in this recognition task.
Both d' and Beta were calculated for each subject based
on the 60 responses on the recognition tasks administered at
time one and time two. The measure d' is an index of how
sensitive a subject is to a signal or target, while Beta is
an index of response bias. A higher d' indicates that a
subject needs a stronger signal or perhaps needs to be more
certain that a target has been seen before the subject will

55
endorse it as a previously exposed item. A Beta higher than
one indicates that a subject is biased towards saying "no",
that they did not see the stimulus previously, while a Beta
less than one suggests that the subject is biased towards
"yes" responses, that they did see the stimulus previously
(McNicol, 1972).
In this study, both young and old averaged Beta's
slightly greater than one, suggesting a small bias towards
caution for both young and old (Young mean Beta =1.21,
S.D.=.37, Old mean Beta=1.56, S.D.=.84). Comparisons of
these means suggested that older adults were significantly
more cautious and likely to say "no" than the younger
subjects (t(58)=4.15, p=.05). The older adults' d' was also
significantly greater than the young adults, suggesting that
older subjects had a higher response criterion and were more
accurate discriminators (Young mean d'=1.75, S.D=.80, Old
mean d'=2.19, S.D.=.84; t(58)=4.18, p=.05).
Electrodermal Response to Recognized
and Unrecognized Targets
During the recognition phase of this study,
electrodermal response (EDR) was measured, as an index of
sympathetic arousal. A 2(Age Group) x 4(Response Type: true
positives, true negatives, false positives, and false
negatives) ANOVA on the range corrected EDR was not
significant for the overall model (F(7)=1.90, p=.066) and
did not suggest an age by response type interaction or an
overall effect for age group. A separate ANOVA examining

56
the effect of Age Group and Stimulus Type (i.e., target
versus distractor) was significant (F(3,3566)=3.40, p=.017),
suggesting an overall effect of Stimulus Type
(F(1,3566)=9.08, p=.0026, w^.002), but no effect of Age
Group (F(l,l)=.17/ p=.69) or interaction (F(l,l)=.96,
p=.33). These data suggest that regardless of a subject's
overt response or age group membership, they show greater
sympathetic activation to targets than to distractors. This
relationship is shown in Figure 6. However, the omega
squared value suggests that whether the stimulus is a target
or distractor accounts for only a very small proportion of
the variance in EDR.

E30H p.» fto # i i o n
R
a
n
S
e
Figure 6. Electrodermal Response to the Different Response Types.
Ul

EXPERIMENT Is DISCUSSION
This study examines whether exposure to an arousal
inducing Critical Event (CE) has the same effect on young
and old adults' memory for both the CE itself and the
stimuli immediately surrounding the CE.
It was found that these two age groups did not differ
significantly in education or intelligence, as measured by
the Vocabulary subtest of the WAIS-R, so it is unlikely that
differences in memory performance which did emerge could be
attributed to formal schooling or intelligence. Anxiety and
depression measures were included to insure that the older
age group was not significantly more anxious or more
depressed than the younger, since increased anxiety or
depression has been suggested as one possible explanation
for age differences found between younger and older adults.
In this sample the two groups were significantly different
in their responses on the STAI and the CES-D, but it was the
younger age group that was endorsing items suggestive of
higher levels of anxiety and depression. Since virtually
all the literature on depression and anxiety and memory
performance suggests that more anxious and depressed
subjects will do less well on memory measures, and it was
the younger adults who reported more anxiety and depression
58

and who performed better on the memory measures, it is
likely that these differences would minimize rather than
exaggerate age differences.
59
The pattern of results obtained on recognition and
recall measures, when comparing younger and older adults, is
consistent with previous research in which significant
differences are found on tests of free recall, but small or
insignificant differences are found on tests of recognition.
This supports the notion that the memory patterns seen in
this sample of young and old adults represent reliable,
replicable effects that have been demonstrated across
repeated studies.
Inspection of the effect of item position on recall
shows that, just as in previous research, both younger and
older adults show both primacy and recency effects.
However, the introduction of the CE in the middle of the
list influences the pattern of recall of young and old
differently. While younger and older adults are likely to
remember the critical event, induced retrograde amnesia
appears to be present only in the young adults. One
possible contributor to the lack of amnesia for older adults
was that, although only a trend, fewer older adults recalled
the CE. It was possible that only those older adult
subjects who failed to recall the CE would fail to show
retrograde amnesia, which could have altered the overall
pattern of recall; however, analysis of the recall patterns
of the older adults who did recall the CE compared with

60
those who did not, failed to find a difference in the effect
of the CE between these two subgroups of older adults. Even
the older adults who, like the younger adults, recalled the
CE did not show evidence of retrograde amnesia. This
suggests that item specific processing sufficient to
increase recall is not necessarily sufficient to induce
amnesia in older adults.
Additionally, young and old are affected differently by
different types of CE's. In young adults both CE' s (i.e.,
photograph of a starving child and photograph of a normal
child) resulted in equal recall of the CE, the more
disturbing CE is associated with more pronounced retrograde
and anterograde amnesia. In older adults, even though the
starving child photograph was more likely to be remembered,
there was no evidence that it resulted in a substantial
decline in recall for surrounding items.
This lack of disruption among the elderly is not easy
to explain. These data do not support the notion that older
adults are chronically over-aroused and that their memory
for items are more easily disturbed since they were, in
fact, less likely to exhibit disrupted memory than the
younger adults. It may be that the already lower memory
performance on the center items in the older adults group
may have contributed to a lack of amnesia, since there was
less of a distance for them to decline. But younger adults'
memory for the item immediately preceding the critical event
was even lower than the older adults' memory. Thus, an

61
explanation based on overall level of recall of middle items
does not seem adequate to account for this data.
How arousing stimuli affects memory performance in
older adults does appear to be clearly different from how it
affects memory performance in the young. The younger adults
seem to overfocus on the distinctive stimulus, to the
detriment of memory for surrounding items. This effect is
even more extreme when stimuli are disturbing. Older
adults, whose memory for distinctive items does not increase
as much as younger adults, do not seem to overfocus and lose
surrounding information. This difference however, does not
appear to influence overall recall, but only which items are
recalled. Since it has been suggested that manipulations in
tonic arousal influences total recall performance, the fact
that only the memory for the middle items was influenced by
the CE supports the notion that this experimental
manipulation primarily influenced phasic and not tonic
arousal.
This study also allowed us to examine response types of
younger and older adults on recognition tasks and to compare
electrodermal recognition of items. The analysis of these
results suggest different response biases and types of
errors likely with young as compared to older adults, with
younger adults more likely to have false positive responses
and older adults more accurate discriminators and being more
cautious than the young in endorsing both targets and
distractors. This response bias does not provide a

62
sufficient explanation for the item specific memory
differences found between younger and older adults, since it
was specifically the items immediately surrounding the
critical event that showed greatest differences between
young and old adults. It is possible that the older adults
tendency towards caution contributed to their reporting the
CE less frequently (although again, this difference was not
statistically significant) but cannot explain why the older
adults failed to show a decrement in memory for items
surrounding the CE.
Analysis of EDR suggested that both younger and older
adults tended to respond more strongly to targets than to
distractors, regardless of whether the target was explicitly
recognized, although target versus distractor status
accounted for a very small proportion of the variance in
EDR. No age differences or interactions were demonstrated
in this phenomenon. This suggests that in older and younger
adults, relative sympathetic arousal response to previously
exposed stimulus is an unlikely source for memory
differences. However, these measures were taken only during
the recognition portion of this study and it is noteworthy
that the overt, as well as covert, recognition failed to
demonstrate age differences as well. Differences in arousal
during acquisition or recall may still be present and
contribute to age-related memory differences.
The age differences found in reported levels of anxiety
and depression measures may also reflect the lower level of

63
arousal in older adults and may have contributed to the
different patterns of memory performance found in the two
age groups. The results may be altered with an older adult
group with higher levels of anxiety or depression, or with a
younger adult group with lower levels of anxiety and
depression. Although it is unlikely that the age
differences in anxiety and depression account for the age
differences in memory performance since both groups were
within normal limits on the measures of anxiety and
depression, additional research including samples of
subjects with more variability in tonic arousal would
clarify this issue.
It is also possible for the Yerkes-Dodson curve to
influence age differences in three different ways. First,
older and younger adults, due to cohort differences or
differences in their experience or lifetime experiences or
exposure to disturbing photographs or stimuli may be
responding differently to the photographs presented as the
critical events which could result in arousal levels being
at different points on the curve for the two age groups.
Different photographs or different types of distinctive or
disturbing events may result in arousal levels for young and
old at different places on the Yerkes-Dodson curve that has
been hypothesized to influence performance. Secondly, tonic
arousal differences between young and old may result in the
Yerkes-Dodson curve itself being different for two age
groups. Finally, there could be an interaction between the

64
age-related differences in reaction to the stimuli and the
different curves for the two age groups. It is not possible
to explore this possibility within this study since only two
levels of arousal were sampled, but additional research
sampling more points on the phasic arousal curve could show
a different relationship between arousal and aging.

EXPERIMENT 2: METHODS
The Interaction of Age and Increased
Tonic Arousal on a Supraspan List Learning Task
Overview and Rationale
Whereas the first experiment manipulated arousal
processes associated with individual items and observed the
resulting effects on item position data, the second study
manipulated overall (tonic) levels of physiologic arousal
and evaluate its effects on general levels of recall and
recognition. Psychophysiological studies of the elderly
have been interpreted to suggest that tonically, the elderly
are both less aroused (e.g., Thompson & Nowlin, 1973) and
more highly aroused than the young (e.g., Woodruff, 1985).
While a low level of white noise and moderate exercise
increase arousal and improved delayed memory performance in
a group of college students (Eysenck, 1977), a white noise
condition has been shown to interfere with the performance
of an elderly group while exercise caused an improvement of
an elderly group's performance on another cognitive task
(Woodruff, 1985). This illustrates that arousal may not be
a single state variable, and that differences may exist
between different kinds of arousal states. Young and old
may be influenced differently by changes in state arousal.
Other studies have suggested that heightened arousal may
65

66
interfere with semantic encoding of information (Eysenck,
1976; Schwartz, 1975). Since changes in strategy use and
semantic clustering has also been suggested as a possible
source of declining memory in the elderly (Poon, 1985), this
raises the possible role of arousal as a moderating variable
in these effects.
This experiment examines the effect on memory of
activities that have been known to moderately increase or
decrease levels of physiological arousal in both young and
old adults. A modified version of the California Verbal
Learning Test (Delis et al., 1983) was used to measure
immediate and delayed recall, recognition, and semantic
clustering. An exercise and a rest condition were used to
alter physiological arousal.
This experiment was designed to provide information on
how tonic arousal interacts with encoding processes in
memory. If the older group's performance improves more with
moderate exercise than with no exercise, this may be
construed as supportive of the under-arousal hypothesis
while if the opposite pattern results that may be more
supportive of the over-arousal hypothesis. In comparison to
the younger group, if they do not improve as much or at all
under the exercise condition, this would suggest that if
under-arousal is indeed a problem, increasing physiological
arousal is not sufficient to solve it.

67
Subi ects
Subjects in this experiment were recruited and screened
as outlined in Experiment 1. Again there was a young and an
old adult group, each containing 48 subjects. The younger
group in this sample were between 18 and 38 years old
(mean=19.61, S.D.=1.70) and had completed between 13 and 16
years of eduction (mean=14.2, S.D.=1.0), while the older
group was between 60 and 80 years old (mean=69.35,
S.D.=5.66) and reported completing between 8 and 20 years of
education (mean=15.6, S.D.=3.0).
Experimental Conditions
Immediately prior to exposure to the word list, 24
subjects from each Age Group were asked to exercise for five
to seven minutes and the 24 were asked to rest for five to
seven minutes. 24 subjects in each of the Age Groups were
then asked to engage in the same activity and 24 were asked
to engage in the alternate activity immediately prior to
delayed recall. During the rest condition subjects remained
seated in a recliner. During the exercise condition
subjects walked inside Shands Teaching Hospital.
Materials and Apparatus
As in experiment 1, the STAI, CES-D, and Vocabulary
subtest of the WAIS-R were administered to test for
differences in reported anxiety or depression or general
intelligence. To measure memory performance a modified
version of the California Verbal Learning Test was
constructed. This test consisted of a 20 item word list,

68
with each item fitting into one of five categories. The
word list was read three times, instead of the standard five
times, and subjects were asked to report all items they
could recall after each presentation. After a thirty minute
delay, free recall, cued recall, and forced choice
recognition were also administered. The forced choice
recognition test consisted or 42 items, the 20 targets and
22 distractors (See Appendix B).
Since it has also been suggested that younger and older
adults may react differently to the testing situation
itself, data was also collected about subject's reactions to
the distractor tasks. In addition to collecting the
physiological measures of arousal before and after engaging
in either rest or exercise, these measures were also taken
at the beginning of the 30 minute delay, and immediately
after learning the word list in order to be compared with
these same measures after engaging in the distractor tasks.
Subjects were also asked to subjectively rate how they
were feeling on the Self Assessment Mannikin or SAM (Hodes,
Cook, & Lang, 1985). This measure asks subjects to place
themselves along a nine point continuum on three different
dimensions: a happy to sad dimension, an excited to calm
dimension, and a feeling in control to feeling out of
control dimension. These measures provide both objective
and subjective information about unintended changes in
arousal produced by participating in this study. Again,
this was used as a manipulation check and to rule out

alternate explanations for the differences seen in memory
performance between young and old.
69
Both immediately before and immediately after this five
to seven minute period blood pressure and pulse rate were
measured. These measures were taken as a check on the
experimental manipulation because they are very responsive
to increased physical activity (Clark, Milberg, & Ross,
1983). Blood pressure and heart rate were chosen because
they can be measured quickly and easily. These measures
were taken using a Dinamap Adult/Pediatric and Neonatal
Vital Signals Monitor, Model 1846 SX. This monitor
automatically provides a measure of systolic and diastolic
blood pressure and pulse rate.
Procedure
After arriving for their appointment, subjects read and
signed a consent form. Baseline blood pressure was taken
after subjects had read and discussed the consent form with
the examiner. Those assigned to the relaxation condition
sat in a chair and were then asked to relax for five to
seven minutes. Those assigned to the exercise condition
walked around the health center with the examiner for five
to seven minutes.
Immediately after the five to seven minute period blood
pressure was taken and the modified CVLT was administered.
A third blood pressure reading was taken after the modified
CVLT was administered. During the thirty minute delay
subjects were administered the Vocabulary subtest from the

70
WAIS-R, the CES-D, and the STAI. After a twenty minute
delay, a fourth blood pressure reading was taken and
subjects were again asked to either relax for five to seven
minutes or exercise for five to seven minutes. Half of the
subjects in each group engaged in the same activity as they
did originally and the other half engaged in the alternate
task. After another blood pressure reading, subjects were
asked to recall all items from the original list, first with
no cues (delayed free recall) and then with category cues
(delayed cued recall). Finally, subjects were read a list
of 42 items and asked to say "yes" if an item had been on
the list and "no" if it had not.
The following dependent measures were collected: 1) The
number of CVLT items correctly recalled after the first,
second, and third repetitions, and after a 30 minute delay.
2) The Observed Semantic Clustering Score for each of the
previously described times. Subjects were given one point
each time they recalled one word after another that was from
the same semantic category. Credit was given for a semantic
cluster only if it was the first time each of the words had
been recalled in that trial and if the word was actually a
target. 3) The Cluster Percentage Scores for each of the
above described times. This was calculated by dividing the
Observed Clustering Score by the maximum number of clusters
possible given the number of correctly recalled items on
that trial.

EXPERIMENT 2: RESULTS
Psychometric Test Performance
On the WAIS-R Vocabulary subtest younger adults
achieved an average raw score of 49.0 (S.D.=7.1) and older
adults achieved an average of 57.7 (S.D.=9.0), with mean age
scale corrected scores being in the high average range for
both younger (mean=11.7, S.D.=1.9) and older adults
(mean=13.4, S.D=2.5). On the STAI the younger group had an
average state score of 36.2 (S.D.=8.1) and an average trait
score of 37.5 (S.D.=9.9) compared to the older groups
average state score of 31.1 (S.D.=8.1) and average trait
score of 32.2 (S.D.=7.0). On the CES-D, younger adults had
an average score of 17 (S.D.=10.6), while older adults
averaged 6.7 (S.D.=6.0).
Education, WAIS-R raw and age corrected scaled scores,
State and Trait portions of the STAI, and CES-D scores were
subjected to t-tests to test for differences between age
groups on these measures. Even when reducing significance
to control for the number of comparisons, the two groups
were significantly different from each other on all these
measures. The older group were more highly educated
(t(94)=3.19, p=.0019), achieved a higher score on the WAIS-R
71

72
vocabulary subtest (raw vocabulary, (t(89)=.15, p=.0001),
and age corrected scaled score, (t(94)=3.66, p=.0004),
reported less anxiety on both state and trait anxiety
measures (state, t(94)=3.06, p=.0029, trait, t(94)=2.97,
p=.0037) and reported fewer symptoms of depression on the
CES-D (t(94)=5.82, pc.0001).
These measures, as in Experiment 1, were for the most
part included to ensure that the older adults were not less
educated, less intelligent, more anxious, or more depressed
since all those factors could contribute to lower
performance on memory measures. As reviewed in the Results
section of Experiment 1, total recall and differences
between recall and recognition have been found to be
influenced in depression, while both total recall and
recognition are thought to be influenced by anxiety. These
age differences however, are likely to have minimized rather
than exaggerated any age differences in memory performance
found in this study.
Free Recall. Cued Recall, and Recognition
The number of items recalled and recognized by the two
age groups are shown in Table 4. A 2(Age Group) by 3(Test)
ANOVA was performed on this data to determine whether the
older and younger adult samples performed similarly to
previously reported studies with largest age differences on
tests of free recall, smaller but still significant
differences on tests of cued recall, and small or no age

73
differences on tests of recognition. This analysis
suggested that this sample did indeed follow this pattern.
Table 4
Means and Standard Deviations for Recall
Performance on Modified CVLT
(20 minute delay)
Free Recall
Cued Recall
Recognition
Young
14.43
14.79
19.06
(2.5)
(2.5)
(0.9)
Old
11.72
12.96
18.45
(3.7)
(2.9)
(1.5)
Although
older adults had
lower average
scores on all
three memory measures, the ANOVA suggested a significant Age
by Test interaction (F(2,93)=10.09, p=.0003, ^=.02) and
significant main effects of Age group (F(l,94)=15.85,
p=.0001, w^=.134) and Test (F(2,188)=341.32, p=.0001,
w2=.lS). Bonferroni t-tests, correcting for the three
comparisons, revealed that younger and older adults are
significantly different on free and cued recall after a 30
minute delay (Free recall: t(83)=4.22, pc.Ol; Cued Recall:
t(94)=3.32, pc.Ol). However, the two groups did not perform
differently on the recognition task (t(82)=2.38, p>.05).
Additional analyses, using Bonferroni t-tests, showed that
while both younger and older adults improved significantly
with recognition memory tests in comparison to both free and
cued recall (all pc.Ol), only the older adults were helped

significantly by cuing (young, t(47)=1.59, p>.ll, old,
t(47)=4.79, p<.01).
74
Effects of Exercise. Rest, and Distractor
Tasks on Measures of Arousal
The average effects of exercise and rest on pulse rate,
in beats per minute, and diastolic and systolic blood
pressure, in millimeters of Mercury, are presented in Table
5. Both absolute change and percent change from baseline
are presented. These data suggest that the exercise
manipulation had its desired effect both before the learn
trials and before final recall of the list.
All three physiologic measures increased after
exercise, but tended to decrease or remain about the same
after resting for five to seven minutes. Changes for the
young and old adults are also presented separately in Table
5. These data were subjected to two separate 2(Age Group)
by 2(Activity: Exercise or Rest) by 3(Physiologic Measures)
ANOVA's for both acquisition and test conditions, first
using the absolute change scores and then using the percent
change from baseline scores.
For the both acquisition ANOVA's, using the absolute
change scores there was a significant interaction between
Age Group and Acquisition Condition only for Systolic Blood
Pressure (F=(l,95)=6.76, p=.01, w2=.Q22). Significant main
effects for activity were found on all three physiologic
measures (Pulse Rate: F(1,95)=100.14, p=.0001, ^=.5065,
Systolic Blood Pressure. F(l,95)= 151.98, p=.0001, w2=.5971,

75
Table 5
Mean Change After Rest and Exercise
Conditions
Response
Pulse Rate
: Measure
Systolic B.P.
Diastolic B.P.
Chance
Chance
Chance
Learn Condition
Exercise
+ 14.9
+21.8
+3.7
(+21%)
( + 6%)
(+17%)
Rest
+ .02
-7.3
-4.3
(+.2%)
(-6%)
(-6%)
Test Condition
Exercise
+ 14.1
+20.1
+4.1
(+20%)
(+7%)
(+17%)
Rest
-1.3
-4.9
-1.9
(-2%)
(-3%)
(-4%)
Learn Condition
Exercise
Young
+16.1
+ 17.5
+4.8
(+23%)
(+8%)
(+15%)
Old
+ 13.6
+26.1
+2.5
(+20%)
(+5%)
(+20%)
Rest
Young
+1.1
-5.4
-4.5
(+2%)
(-6%)
(4%)
Old
-1.1
-9.1
-4.0
(-1%)
(-6%)
(-7%)
Test Condition
Exercise
Young
+ 17.1
+ 20.2
+5.6
(+24%)
( + 9%)
(+18%)
Old
+ 11.2
+ 19.9
+2.7
(+16%)
(+4%)
(+16%)
Rest
Young
-0.1
-4.0
-2.0
(-.3%)
(-3%)
(-3%)
Old
-2.3
-5.9
-1.9
(-3%)
(-3%)
(-4%)

76
Diastolic Blood Pressure: F(l,95)= 40.65, p=.0001, w^=.2945)
but there was no main effect for Age Group (.11 < p < .58).
The analysis using the percent change scores was essentially
identical with p values of the same magnitude and omega
square values differing by less than three percent.
An identical ANOVA using the change scores from Test
Condition revealed significant main effects of Test
Condition for all three physiologic measures (Pulse Rate:
F(1,95)=157.80, p=.0001, ^=.5946, Systolic Blood Pressure,
F(1,95)= 143.59, p=.0001, ^=.6015, Diastolic Blood
Pressure: F(l,95)= 32.81, p=.0001, ^=.2458) and a main
effect of Age Group for Pulse rate (F(1,95)=10.68, p=.015,
w^= .0367) was also found. There were no significant
interactions between Test Condition and Age Group. Again,
the analysis using the percent change data was essentially
identical, with similar p values and omega squared values
that differed by less than three percent.
These analyses suggest that the exercise manipulation
significantly increased physiologic arousal, while rest did
not. The main effect of Age Group and the Interaction
between Age Group and Arousal Level were not demonstrated
consistently in the physiologic measures and accounted for a
relatively small percentage of the variance compared with
the amount of variance consistently accounted for by
exercise condition. Young and old were both affected in the
predicted directions by the exercise manipulation, but when
there was an Exercise by Age Group or main effect of Age

77
Group effect, it was the younger adults who tended to show a
greater increase in physiologic arousal.
Because it has also been suggested that older adults
find the act of engaging in psychological tests more
arousing than do younger adults, this was also investigated.
Immediately after learning the word list, the three
physiologic measures were taken and subjects were asked to
complete the Self Assessment Mannikin (SAM) to subjectively
rate their feelings on the valence, arousal, and dominance
dimensions. Change scores were calculated for the three
physiologic measures and three SAM ratings and subjected to
t-tests with Age Group as the between subjects variable.
None of the tests of the physiologic measures suggested
there were significant differences between age groups (.14 <
P < *56), and only on the valence dimension did young and
old differ significantly on SAM (t(75)=2.88, p=.0052), with
younger adults reporting they were happier than older
adults.
From pre- to post- distractor items, the average pulse
rate declined 2.4 beats per minute (bpm) for young and
declined 1.27 bpm for the older adults. Systolic blood
pressure increased an average of 2.8 millimeters of Mercury
(mmHg) for young, and decreased 0.06 (mmHg) for older
adults. Diastolic blood pressure for both young and old
changed less than one mmHg. While younger adults rated
themselves an average of 0.04 points happier, older adults
rated themselves 0.625 points less happy (on a scale of

78
nine) after engaging in the distractor tasks. On average,
both young and old adults rated themselves as approximately
0.5 points less aroused, and 0.6 (young) and 0.8 (old)
points more dominant after engaging in the distractor task.
Overall, both objectively and subjectively this data
suggests that neither young nor old seemed to be
significantly affected either physiologically or emotionally
by the distractor tasks.
Exercise Condition and Memory
The first effect of interest was whether the exercise
versus no exercise manipulation prior to acquisition
affected recall, observed clustering, or cluster percentage
differently for the young and old. A 2(Acquisition State)
by 2(Age Group) by 3(Repetition) repeated measures ANOVA,
with time as the repeated measure, suggested that there was
no Repetition by Age Group by Acquisition State interaction
(F(2,91)=.078, p=.92) and no Age Group by Acquisition State
interaction (F(l,92)=1.5, p=.22). The Repetition main
effect was significant (F(2,91)=359.96, p=.0001, w^=.79)
with all subjects increasing the number of recalled items
over time. A main effect of Age Group was also found (F(l,
92)=10.84, p=.0014, w2=.0933) with older adults consistently
recalling fewer items than younger adults.
Two additional 2(Age Group) by 2(Acquisition State) by
3(Repetition) Repeated Measures ANOVA's were conducted on
the Observed Cluster scores and Cluster Percentage Scores.
For both these analyses, there were no interactions that

79
even approached significance. Again, the Repetition main
effect was significant (Cluster Observed. F(2,91)=92.23,
p=.0001, w^=.4892, Cluster Percentage. F(2,91)=26.81,
p=.0001, w^=.2079). Both Cluster Observed and Cluster
Percentage scores increased over time.
The second effect of interest was whether a "state
dependent" learning effect had been demonstrated and whether
this effect differed between age groups. To test this, data
were reorganized and each subject's data were placed in one
of two cells depending on whether their activities before
acquisition and memory testing was the same or different.
"Same" subjects were subjects whose activities prior to list
acquisition and memory testing were either exercise or rest
(i.e., rest-rest or exercise-exercise). "Different"
subjects were those whose activities prior to learning and
memory testing were different (i.e., rest-exercise or
exercise-rest). These data are presented in Table 6.
Table 6
Encoding/Test Correspondence
Same Different
Group
Free Rcl
Cluster
Clust %
1
1 Free Rcl
Cluster
Clust %
Younger
14.75
6.95
63.09
1
| 14.13
5.21
48.79
Older
12.92
5.63
57.70
1
| 10.54
1
3.88
45.21
After being
organized
in this
way, Free
Recall,
Observed Clustering, and Cluster Percentage data were each

80
subjected to separate 2(Age Group) by 2(Learn-Recall
Correspondence) Repeated Measures ANOVA's. All three
ANOVA's had p values less than .02 for the models, but there
were no significant interactions. For both Delayed Recall
and Clustering Observed there were main effects for both Age
Group (Delayed Recall; F(l, 92)=18.99, p=.0001, w^.1502,
Cluster Observed: F(1,92)=4.05, p=.027, ^=.0379) and Learn-
Recall Correspondence (Delayed Recall: F(l,92)=5.82, p=.018,
w^=.0403, Cluster Observed: F(l,92)=8.7, p=.004, ^=.0721).
However, when Clustering Scores were corrected for the
number of items recalled in the Cluster Percentage analysis,
Age Group as main effect was not significant (F(1,92)=.99,
p=.3218, w^c.OOOl), but Learn-Recall Correspondence remained
significant (F(l,92)=8.84, p=.0038, ^=.0762). This
analysis suggests that while older adults recalled fewer
items than younger adults after a delay, both younger and
older adults tended to recall more items if they were asked
to recall the items after engaging in the same activity as
during the learn phase. Clustering appeared to be
influenced by age only when not corrected for the total
number of items recalled, but both cluster scores tended to
be higher when subjects had engaged in the same activity
immediately before learning the list and immediately before
recalling the list. This suggests both a state dependent
learning and state dependent clustering effect.

EXPERIMENT 2: DISCUSSION
Just as in Experiment 1, anxiety and depression
measures were included to ensure that older adults were not
more anxious or more depressed than younger adults, since
those conditions have been suggested to decrease memory
performance. In this sample, it was also the younger adults
whose responses suggested higher levels of both anxiety and
depression. In addition, the older adults tended to have
slightly higher levels of education and achieved higher
scores on the WAIS-R Vocabulary subtest. These differences
were not judged to be problematic in this study since these
factors would tend to minimize, rather than maximize, age
differences. Despite this, the previously described
patterns of age differences where still found (i.e., largest
age differences on tests of free recall, older adults
benefitting more from cuing than younger adults, and minimal
or no differences found on recognition tests).
Under-arousal theories of aging and memory would have
predicted that the older adults would have benefitted from
the increased arousal associated with exercising prior to
learning the word list. There also had been some
suggestions that increased arousal is associated with
81

82
decreased semantic clustering (Woods, 1975). In this study,
despite physiologic evidence of increased arousal from the
exercise, neither young nor old appeared to benefit from
either rest or exercising immediately prior to learning the
word list, but consistently showed age differences in which
older adults recalled fewer list items than did younger
adults. Both younger and older adults increased the number
of items recalled with each successive exposure to the list,
and showed increased semantic clustering with repetition.
The fact the semantic cluster percentage also increased
after each repetition suggests that this increase cannot be
attributed to increased overall recall levels, but suggests
increased list organization with increased exposure. This
increased organization after each repetition is evident with
both younger and older adults.
The discrepancy between the results of this study and
previous research may be due to differences in how arousal
was manipulated and to the degree in which the to-be-
remembered word list could be organized for later recall.
The results may be different if cortical rather than just
physiological arousal is altered since it is likely that
cortical arousal does not influence memory in the identical
way physiological arousal influences memory performance. It
is also possible that the use of semantic organization
strategies influences memory more strongly than does arousal
state and the effect of arousal could be seen if the list
was not organizable into semantic categories.

83
State dependent learning effects have been demonstrated
repeatedly with younger adults, but have not been
demonstrated previously with older adults. This study
successfully showed that, for both young and old, being in
the same general state of physiological arousal immediately
prior to acquisition and immediately prior to recalling a
list enhances not only learning, but also the amount of
semantic clustering subjects demonstrate. No age
differences or interactions were found, which is consistent
with Hess and Higgin's (1983) study in which older adults
appeared equally competent as younger adults in using
general context to enhance memory performance.
Being in the same state at recall also seems to enhance
semantic clustering for both younger and older adults. If
this was due simply to the increase in number of items
recalled, this increase should disappear in the semantic
cluster percentage (which corrects for the number recalled),
but this was not the case.

GENERAL DISCUSSION
This paper began by describing behavioral changes in
memory and arousal that have been associated with normal
aging, reviewing how memory and arousal are believed to
interact in normal young adults, reviewing the brain areas
believed to be important in memory and arousal, and
suggesting what brain changes associated with aging might
influence this interaction in older adults. Arousal is a
complex phenomenon, comprised of both the background (tonic)
activity and the phasic (stimulus linked) reaction to an
event. The two studies described above examine both phasic
and tonic arousal in an effort to determine if either or
both appear to influence memory differently in older adults.
In these studies, differences between younger and older
adults were found in how phasic (event related) arousal
influenced memory. While a distinctive stimulus was
remembered better by both younger and older adults, memory
for surrounding items was only disrupted in younger adults.
Additionally, a stimulus that was more disturbing to younger
adults and resulted in more profound amnesia (compared to
another distinctive but less disturbing stimulus) did not
affect the memory of older adults at all. Tonic arousal, or
84

85
the state of an individual, seemed to influence older and
younger adults' memories similarly, since both groups
appeared able to use correspondence between acquisition and
retrieval state as a cue to assist in recall. State
dependent learning was present in younger and older adults,
with being in the same state at learning and recall
enhancing both free recall and semantic clustering in both
age groups.
The results of these two studies do not support a
simple over-arousal theory to explain the differences in
young and old on memory tasks. Increasing arousal did not
interfere with memory performance in old adults in
Experiment 2, as one might predict if the older adults were
already over-aroused, although it is possible that even
higher levels of physiologic arousal or alterations in
cortical arousal may influence the two groups differently.
Findings from Experiment 1 would also argue against an over¬
arousal interpretation since fewer older adults remembered
the arousing distinctive stimulus. Secondly, memory for
surrounding items was less, not more, disturbed for older
adults compared to younger adults, despite speculation that
increased arousal plays an important role in induced amnesia
for surrounding items.
Instead, these data could be used to support an under¬
arousal explanation for differences between young and old in
memory performance. Although increasing physiologic arousal
also failed to enhance memory in younger adults, it is

86
possible that increasing cortical rather than physiological
arousal might enhance memory. Since it is impossible to be
certain where on the Yerkes-Dodsen curve the experimental
manipulations sampled when only two points are sampled, it
is also possible that arousal was either not increased
enough or increased too much to facilitate memory. The
lower rate of recall of the distinctive stimulus by the
older adults could be explained by the under-arousal
hypothesis or could be due to a smaller reaction to what is
distinct in the older adults. However, this age difference
was only a trend and not statistically significant. Older
adults were also more likely to recall the more disturbing
or distinctive of the two critical items, perhaps suggesting
that they needed higher arousal, compared to younger adults,
in order to remember items at the same level. The fact that
amnesia for surrounding items was not induced, may also
support the notion of lowered arousal in the older adults.
In this instance, it appears to be advantageous for older
adults to be less highly aroused than the younger adults
since their memory for surrounding items was not disturbed,
while younger adults' memories were disrupted. The older
adults lower reported symptoms of anxiety may also reflect
their lower level of tonic arousal.
There were no age differences in the ability to
autonomically discriminate between targets and distractors
in the context of the recognition task. Both younger and
older reacted more strongly to targets than to distractors

87
in a recognition task, and for both groups, responses to
targets were larger regardless of whether the subjects
overtly recalled the items. It has been suggested that this
phenomenon may be another measure of implicit memory or
memory without awareness (Bauer, 1984). Previous research
had suggested that some forms of implicit memory in young
and old adults differ (Chiarello & Hoyer, 1988); the results
of this study suggest this is an area in which young and old
do not differ. It appears that young and old are equally
able to use or ignore physiologic response to stimuli as a
cue for recall, since both patterns of response and overt
recognition were not significantly different in these two
populations.
Although it is difficult to be certain how the patterns
of behavior in this study reflect age-related brain changes,
it is possible to speculate based on the literature reviewed
previously. The amygdala was suggested as important in the
regulation of arousal related to the input of information,
while the basal ganglia is associated with differences in
levels of activation. The results of Experiment 1 may
reflect the age-related changes documented in these two
areas since conditions at input appear to influence memory
differently in the younger and older adults, and the most
likely explanation for this is differences in the amount of
activation or processing each group engages in reaction to
the two distinctive stimuli. The hippocampus is believed to
be important in the mediation of arousal and memory and in

88
determining what is memorable. It is possible that these
studies reflect different hippocampal functions being
variably affected by age. State dependent learning, which
could be considered part of the mediation of memory and
arousal function, is still intact as demonstrated in
experiment 2. Age-related hippocampal differences may be
reflected in Experiment 1 with regard to deciding whether
the CE is memorable relative to surrounding items.
Frontal areas and the orienting response may be changed
with increasing age and this change may be related to the
differences in phasic arousal effects. Changes in the
frontal areas also may be suggested if the failure of older
adults to find the distinctive stimuli as memorable is
attributable to difficulties in releasing from proactive
interference (i.e., older adults are rigidly expecting line
drawings, which would lead to problems in processing the
photograph). One possible explanation for the older adult's
failure to show the same pattern of memory performance as
younger adults in Experiment 1 is that the older subjects
found the Critical Item less distinctive and/or are
distracted from fully processing the Critical Item by the
surrounding items. Either of these explanations could be
related to the frontal lobe changes that Albert and Kaplan
(1980) suggest are at the heart of age-related cognitive
changes.
Age-related changes in the influence of phasic but not
tonic arousal on memory suggest that the previously cited

89
age-related brain changes in the hippocampus and frontal
cortex may have significant effects on how memory and
arousal interact in older adults. Lesions in the reticular
formation have been most closely associated with changes in
tonic arousal in animals, and this brain area has not been
suggested as particularly affected by aging in human autopsy
studies. The results of this study are consistent with this
since the aging process less strongly affects tonic than
phasic arousal. In these two studies age differences were
found only in how phasic arousal influences memory; this
behavioral evidence is consistent with the physiological
findings of these studies.
It is difficult to be certain which brain areas are
specifically affected by aging and how these changes
influence behavior. However, this study is consistent with
previous psychophysiological, physiological, and
psychological studies which implicate frontal lobe changes
and changes in the hippocampus as important in age-related
memory change. To help determine whether the differences
seen in this study between young and old subjects were due
to diffuse brain changes or more specific focal lesions,
such as frontal lobe lesions as suggested by Albert and
Kaplan (1980), repeating experiment one using frontal lobe
patients compared to patients with more diffuse damage, such
as closed head injury patients might be illuminating.
These results also have implications for psychological
theories that have been invoked to explain behavioral age

90
differences. Salthouse (1985) has argued that age-related
general slowing is the most parsimonious explanation for
many differences seen between young and old, including
differences in memory. However, if it is merely slowing
that changes memory, in Experiment 1 it would be predicted
that retrograde amnesia would be more profound in older
adults because they should not have completed encoding of
the previously exposed stimulus by the time the distinctive
slide was shown. It would also be predicted that older
adults would take longer to recover, increasing anterograde
amnesia. Neither of these results was seen here, suggesting
that slowing is not a sufficient explanation for these
behavioral differences.
The role of organization and semantic clustering of
information as an explanation of age differences is less
clear in this study. Although a previous study found that
increased arousal with white noise decreased semantic
clustering (Schwartz, 1975), increasing physiologic arousal
through exercise in this study did not influence the
organization of to-be-remembered material. Differences
between young and old were found in the amount of semantic
clustering, but only when the cluster scores were not
adjusted for the total number of items recalled. When
semantic cluster scores did reflect the number of items
recalled, age differences dropped out, which may call into
question whether the differences in clustering cause the
lower memory performance. In addition, although no

91
instructions to cluster were given during this study, both
young and old increased clustering over time as their recall
increased.
The similarities found in the ability of young and old
to use state as a cue during recall could be seen as
consistent with Hess' (1984) findings that older adults tend
to show more general rather than specific encoding of
information. If the state one is in is viewed as a more
general cue, and this cue was present during encoding, one
would predict no age differences in the ability to use this
information during retrieval. If the phasic changes are
conceptualized as more specific cues, this would also have
predicted greater age differences in the ability of the
older adults to use this as a cue during retrieval.
It is possible that the differences seen between young
and old in their reactions to the Critical Event may be
unique to the Critical Event stimuli chosen or the modality
chosen to test. To examine for these possibilities
additional studies using older adult groups with different
distinctive stimuli would be helpful. Since this pattern of
memory performance is easy to replicate with younger adults
despite variations in stimuli, it is unlikely that a
stimulus change will significantly alter the age differences
and it is most likely that these findings will be
replicated. Replicating this design using verbal rather
than visual stimuli to examine modality specific differences

92
could be more illuminating since modality has been shown to
be an important variable in influencing age differences.
Together, these two studies illustrate ways in which
memory is both different and stays the same across the
lifespan. Although most studies show how age-related memory
changes are detrimental to overall memory performance,
Experiment 1 provides an example of how the differences in
young and old result in the older adults not losing
information relative to younger adults. Additionally, while
a CE or distinctive stimulus and the surrounding items may
be processed differently by young and old, both young and
old appear to be equally influenced by their reaction to
targets and distractors during recognition and their ability
to use their state of arousal to assist in recall. This
argues against the notion that age-related memory
differences can be attributed solely to differences in
retrieval processes. Overall these studies suggest more
questions about the nature of aging and how it may influence
the interaction between memory and arousal than it answers.
However, it also seems to clearly show that arousal and
memory do not interact in exactly the same way in younger
and older adults and that we may be exploring an important
factor in memory and aging.

APPENDIX A: SCREENING QUESTIONNAIRE
Subject Name:
DOB: Education Completed:
1)History of head injury?(LOC?)
2)Neurological Problems? (Epilepsy, stroke, periods of
numbness or tingling or visual disturbances suggestive of
TIA)
3)Psychological problems? (Medication or counselling for
depression, psychiatric hospitalization)
4)History of learning disability?
93

94
5)History of heart disease?
6)Seeing a physician for any medical problems?
7)Any problem with moderate exercise (e.g. walking) for
five to ten minutes?
8)How much exercise in a typical week?
9)Visual or hearing problems that interfere with reading or
hearing normal conversation?
10)Remind subjects to bring or wear glasses or hearing aids
if they wear them. Provide directions to the lab.

APPENDIX B: MODIFIED CALIFORNIA
VERBAL LEARNING TEST ANSWER SHEET
Lets suppose you were going shopping . I'm going to read a
list of items for you to buy. Listen carefully, for when
I'm through I want you to say back as many of the items as
you can. It doesn't matter what order they're in- just tell
me as many as you can.
I'm going to repeat the list. Again, I want you to say back
as many items as you can, in any order, including the items
you have already told me.
List T1 T2 T3 Delay
spatula
drill
plum
vest
bowl
parsley
grapes
paprika
sweater
wrench
chives
tangerines
skillet
chisel
jacket
toaster
nutmeg
apricots
pliers
slacks
95

96
Cued recall: Tell me all the shopping items from
that are:
Spices and Fruits Tools
herbs
Kitchen
Tools
Recognition:
sweater
tires
j acket
wax
apricot
cherries
chives
chisel
pastry
clock
grapes
paprika
ginger
boots
vest
grill
wrench
tapes
pliers
hammer
chimes
toaster
pepper
aspirin
drill
spatula
drums
film
briefcase
tangerines
shoes
skillet
racket
slacks
parsley
apples
plums
rug
vitamins
bowl
nutmeg
soap
the list
Clothing

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BIOGRAPHICAL SKETCH
Carol J. Schramke was born July 12, 1959, in Saginaw,
Michigan. Carol Schramke was the fifth of seven children
born to Frank and Loraine Frost Schramke. The family moved
to Sterling Heights, Michigan in 1967. She graduated from
Henry Ford II High School in 1977. She married Carson W.
Lane in December of 1980 and completed her undergraduate
work at the University of Michigan in 1982, graduating with
distinction and with honors in psychology. Her graduate
work at the University of Florida began in 1985, and she was
awarded a master's degree in Clinical Psychology in 1988.
She will complete her internship at the Portland VAMC and be
awarded her doctorate in Clinical and Health Psychology in
August of 1990.
106

I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of/^Doctor of Philosophy.
LUA
u^r, Ph.D.
¡íussell M. Bau^fc, Ph.D. Chair
Associate Professor of
Clinical and Health Psychology
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of .Doctor of philosophy.
Michael E. Robinson, Ph.D.
Assistant Professor of
Clinical and Health Psychology
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of Doctor of Philosophy.
U¿éó=^ UA
Walter R. Cunningham, Ph.D.
Professor of Psychology
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of Doctor of Philosophy.
Robin L. West, Ph.D.
Assistant Professor of
Psychology
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scppe/and quality, as
a dissertation for the degreeafDoctor/Of /Philosophy.
íhnétJfr' M.' Heilman, M.D.
Professor of Neurology

I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of Doctor of Philosophy.
V'V'kM. ■ Píhi1^——'
?aber F. Gubrium, Ph.D.
Professor of Sociology
This dissertation was submitted to the Graduate Faculty
of the College of Health Related Professions and to the
Graduate School and was accepted as partial fulfillment of
the requirements for the degree of Doctor of Philosophy.
August 1990
Dean, College of Health
Related Professions
Dean, Graduate School
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