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INGEST IEID E20101109_AAAAAN INGEST_TIME 2010-11-09T10:58:37Z PACKAGE UFE0022030_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC
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EFFECT OF EVERYDAY DISTRACTION ON HEALTHY AND COGNITIVELY IMPAIRED
ELDERS' MEMORY FOR STORIES
SHANNON M. SISCO
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
O 2008 Shannon M. Sisco
To Tammy, who at a moment' s notice is ready with fake teeth and Coke-bottle glasses, cherry
tomatoes, more sass than you can shake a stick at, and a reminder to never waste anything I have,
least of all my pretty.
I am first grateful to my mentor, Dr. Michael Marsiske, whose creativity and patience
have guided me in building my own path, and whose wisdom has made each step I take the best
it could be. I also thank my mentoring committee members, Dr. Catherine Price and Dr. Lori
Altmann, whose insight and suggestions on this project were invaluable. I extend special
gratitude to Sarah Cook, who graciously included me in her dissertation proj ect and allowed me
to work with her data, from which this thesis was produced. I thank the ever-supportive Nate,
whose gift for finding ways to take a break is unparalleled, as is his good nature; I also thank
Brian, without whose impromptu dance parties and ad-lib banjo compositions there would be no
House of Awesome. Finally I thank my father and mother, and my brothers Kyle and Brian, for
whom I don't have to be a psychologist or researcher or even anyone terribly interesting, and to
whom I can always come home.
TABLE OF CONTENTS
ACKNOWLEDGMENTS .............. ...............4.....
LIST OF TABLES ................. ...............8............ ....
LI ST OF FIGURE S .............. ...............9.....
AB S TRAC T ............._. .......... ..............._ 1 1..
1 LITERATURE REVIEW ..........._..._ ...............13.......__......
Overview ..........._..._ .. .......... ...............13......
Cognition, Memory, and Aging............... ...............13.
The Utility of Story Memory Measures. ................. ....._._ ...............15. ...
Age Differences in Story Recall ................. ...............16......... ....
Divided Attention in Aging .................. ....... ............ ..........__ ............1
Elders' Performance in Driving Divided Attention Tasks .............. .....................1
Age Differences in Recall Under Divided Attention .............. ...............21....
The Role of Mild Cognitive Impairment ................. ......._ ................21 ...
Introduction to Amnestic Mild Cognitive Impairment. ..........._..._ ................. ......21
Impact of Cognitive Impairment on Story Recall .............. ...............24....
Impact of Cognitive Impairment on Dual-Task Performance ............... ... ........._ ...25
Sum m ary ................. ...............26........ ......
2 STATEMENT OF THE PROBLEM ................. ...............28......... ....
Dual-Task Effect on Precision............... ...............2
Aim One .............. ...............29....
Hypothesis One .............. ...............29....
Dual-Task Effect on Content ....__. ................. ........__. ........2
Aim Tw o............... ...............29..
H ypothesi s Tw o ............... .. ........._.. .. ............... .... ...... ........2
Role of Cognitive Impairment in Dual-Task Effects on Precision and Content ....................30
Aim T hree............... ...............3 0.
Hypothesis Three ................. ...............30........ ......
3 RESEARCH DESIGN AND METHOD S ......... ......._.._.._ ...............31....
Overview. ...._.._................. .......__. ..........3
The Cook Study ................. ...............31..............
Participants .............. ...............32....
Eligibility ................ ...............32........ ......
Recruitment Sources............... ...............32
Study Procedures .............. ...............33....
Screening .................. ......... .. .. ......... .. .. .. ............3
Admini station of Neuropsychological and Experimental Tests ................. .................3 3
Consensus Classification ................. ...............34.................
Neuropsychological Measures ................. ...............35......_._. .....
Telephone Screening Measure .............. ...............35....
Neuropsychological Consensus Measures .............. ...............35....
Experimental Task ................. ...............39.................
Experimental Procedure .............. .. ...............39...
Experimental Measures and Materials .............. ...............40....
Short story measures .............. ...............40....
Short story scoring .............. ...............41....
Scoring reliability ................. ...............42.......... ......
Driving task ................. ...............42.......... ......
4 RE SULT S .............. ...............46....
Overview ................. ...............46.................
Participant Sickness ................. ...............47.................
Preliminary Analyses ................. ...............47.................
V alidity ................. ...............47.......... .....
Reliability .............. .. ....... .... ..............4
Dual-Task Effect on Total Recall ................. .. ............ .... ... ........ ....... 4
Overall Memory Performance between Cognitive Status Groups .............. ..................49
Main Analyses ................. ........ ..............4
Aim One: Dual-Task Effect on Precision............... ...............4
Aim Two: Dual-Task Effect on Content ................................................5
Aim Three: Role of Cognitive Impairment in the Dual-Task Effects ................... ..........51
Follow-Up Analyses ................. ... ............ .... .. ........ .............5
Policy Capturing and Cognitive Status Classification............... .............5
Proportionalized Scoring Relative to Baseline Performance .............. .....................5
5 DI SCUS SSION ................. ...............64................
Overview ................. ...............64.................
Review of Findings ................... ......... ...............65.....
Aim One: Dual-Task Effect on Precision............... ...............6
Aim Two: Dual-Task Effect on Content ................. ....... ........ ...........6
Aim Three: Role of Cognitive Impairment in Dual-Task Effects ................. ................67
Im plications .............. ...............69....
Limitations ................. ...............69.................
Future Directions .............. ...............71....
Conclusion ................ ...............73.................
A SHORT STORIES USED IN THE EXPERIMENTAL TASK .............. ....................7
B DISTRIBUTIONS OF NEUROPSYCHOLOGICAL DATA ................. .......................77
C FOLLOW-UP ANALYSES USINTG SCORES RELATIVE TO BASELINE
PERF ORMANCE ................. ...............79.................
LI ST OF REFERENCE S ................. ...............8.. 1......... ....
BIOGRAPHICAL SKETCH .............. ...............88....
LIST OF TABLES
3-1 Measures used for consensus classification. .............. ...............43....
4-1 Number of participants with complete, partial or no data by cognitive status. .................58
4-2 Means + standard errors of story recall total scores by healthy (N=41) versus
impaired participants (N= 12) ................. ...............58........... ...
B-1 Skewness and kurtosis (N=61) of neuropsychological data distributions by measure......??
LIST OF FIGURES
3-1 Participant visit overview. ............. ...............44.....
3-2 Experiment procedures represented by task condition. ............. ...............44.....
3-3 Calculation of verbatim and paraphrased recall scores ......... ................. ...............45
3-4 Calculation of main idea and detail recall scores............... ...............45.
4-1 Proportion of idea units recalled verbatim or in paraphrase across task conditions
4-2 Proportion of main idea units recalled and proportion of detail idea units recalled
across task conditions (N=53)............... ...............59.
4-3 Proportion of verbatim recall in healthy (N=41) versus impaired (N=12) participants
recall across task conditions............... ...............5
4-4 Proportion of paraphrased recall in healthy (N=41) versus impaired (N=12)
participants across task conditions ................. ...............60................
4-5 Proportion of recall for main ideas in healthy (N=41) versus impaired (N=12)
participants ideas across task conditions............... ...............6
4-6 Proportion of recall for details in healthy (N=41) versus impaired (N=12)
participants across task conditions ................. ...............61................
4-7 Healthy participants' proportions of verbatim and paraphrased recall across task
conditions (N=41). ................ ...............61.......... .....
4-8 Impaired participants' proportions of verbatim and paraphrased recall across task
conditions (N= 12). ............. ...............62.....
4-9 Healthy participants' recall for the proportion of main ideas versus details across
conditions (N=41). ................ ...............62.......... .....
4-10 Impaired participants' recall for the proportion of mail ideas versus details across
conditions (N= 12). ............. ...............63.....
B-1 Histogram representing the frequency distribution of percentile scores for Delayed
Recall on the Hopkins Verbal Learning Test ................. ...............78........... ..
C-2 Comparison of idea units recalled verbatim by healthy (N=41) versus impaired
participants (N=12) across task conditions. .............. ...............79....
C-3 Comparison of idea units recalled in paraphrase by healthy (N=41) versus impaired
participants (N=12) across task conditions.. ............. ...............79.....
C-4 Comparison of main idea units recalled verbatim by healthy (N=41) versus impaired
participants (N=12) across task conditions. .............. ...............80....
C-5 Comparison of detail idea units recalled verbatim by healthy (N=41) versus impaired
participants (N=12) across task conditions.. ............. ...............80.....
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
THE EFFECT OF EVERYDAY DISTRACTION ON HEALTHY AND COGNITIVELY
IMPAIRED ELDERS' MEMORY FOR STORIES
Shannon M. Sisco
Chair: Michael Marsiske
Major: Psychology--Clinical and Health Psychology
This study evaluated how older adults' recall of short stories was affected by simultaneously
performing a low- or high-speed simulated driving task. Specifically, recall was examined in qualitative
terms: did older adults use more paraphrasing than verbatim recall as the driving challenge increased?
Did older adults rely more on recall of main ideas, and remember fewer details, with increasing driving
challenge? Did cognitive status (healthy versus mildly impaired) interact with distraction's effect on
A sample of 46 healthy older adults (61% women; mean age = 76.39 years, mean education =
15.83 years) and 15 older adults with amnestic mild cognitive impairment (66% women, mean age =
79.4 years, mean education = 16.07 years) were asked to recall brief short stories that were administered
under three conditions: no driving, low-speed (30 mph) driving, high-speed (60 mph) driving. Stories
were scored in two ways: 1) as the amount of information recalled verbatim (word-for-word) versus
recall in paraphrase, and 2) as the amount of main idea information recalled versus amount of detail.
Repeated measures analyses of variance were conducted, contrasting the verbatim/paraphrase and main
idea/detail dimensions of recall across the three recall challenge conditions and between the two
cognitive status groups. Analyses revealed that verbatim recall was higher than paraphrase recall in
every condition, F(1, 104) = 99.94, p<.001, and that only verbatim recall decreased when a simultaneous
driving challenge was added. Verbatim recall did not decrease further between the low- and high-speed
conditions. Analyses of main idea/detail recall revealed that recall for main ideas was consistently
higher than for details in every condition, F(1,104) = 380. 17, p<.001. Main idea recall did not decrease
significantly with the addition of the simultaneous driving challenge, but did decrease when the driving
challenge was raised from low to high speed. Recall for details decreased with the addition of the
simultaneous driving, but not when driving speed was increased. Cognitive status was not found to
significantly interact with the effect of distraction; dual-task performance costs were equivalent between
the healthy and impaired groups.
This study demonstrates that when older adults are asked to attend to verbally-presented
information while simultaneously driving, their ability to recall details of that information, and their
ability to remember it verbatim, declines. As the difficulty of the driving challenge increases, older
drivers may additionally recall less of the main points of the information conveyed. This study identifies
another potential risk of distracted driving: when potentially important information (e.g., directions,
alerts) is presented verbally to older drivers, their ability to retain this information may be substantially
This study seeks to examine changes in healthy and impaired older adults' story recall as a
result of performing a simultaneous simulated driving task. First an overview of age-related
changes in cognition, and the effects of age on various forms of memory, will be explored. The
utility of story memory tests for assessing episodic memory will be briefly discussed, followed
by the effects of aging on story recall Next, older adults' performance on dual-tasks will be
addressed, including tasks requiring verbal recall. Finally, the review of older adult performance
in story recall and dual tasks will expand to include the effect of mild memory impairment in
Cognition, Memory, and Aging
The gradual general decline in cognition associated with advancing age is well-known.
The pattern of decline is not uniform (e.g. Singer et al., 2003, Schaie, 1990). Types of cognition
related to acquired knowledge, such as fluency and semantic memory, are relatively preserved.
Types of cognition related to procedural abilities including reasoning, attention, and perceptual
speed are more greatly affected by advancing age. These cognitive changes are subserved by
relevant changes in brain structure. Beginning around age 30 and continuing across the adult
lifespan, there is a global reduction in brain volume. However, this pattern of change is also not
uniform, and is seen most prominently in the prefrontal cortex, followed by the temporal and
parietal areas (e.g., Head, 2002). There is also a decline in the integrity of white matter tracts,
which is most significant in the prefrontal cortical regions (Mosley et al., 2002, Head et al.,
Aging produces varied effects on the different subtypes of memory. Possibly the most
well-known and pronounced effect of aging is on the ability to consciously recall specific events
or episodes, referred to as episodic memory (Zacks et al., 2001). Episodic memory appears to be
relatively stable until around age 60, when it declines at an accelerated rate with increasing age
(Ronnlund et al., 2005). The age-related decline in episodic memory is purported to reflect a
weakened encoding capacity. Some argue this is the result of generalized cognitive slowing,
which reduces the speed of encoding and affects the total amount of information stored (e.g.,
Verhaeghen & Salthouse., 1997). Other theories infer encoding is impacted by deficits in
specific executive components such as working memory, inhibitory control (e.g. Lovden, 2003),
or coordination of cognitive processes (e.g., Fisk & Sharp, 2004). The findings on declines in
prefrontal cortical volume and function would support these theories, although it remains
unresolved whether age-related changes in episodic memory are the result of reductions in
volume or of degraded white matter tracts.
Aging also produces a reliable and significant decrease in worlong memory capacity, or
the ability to simultaneously store and manipulate information. Working memory, like the
cognitive components hypothesized to sub serve episodic memory, is generally agreed to be a
function of the prefrontal cortex. Memory span measures, such as reading span, are commonly
used to assess working memory. In reading span tests, persons concurrently read a series of
sentences and try to remember the last word of each sentence, and are asked after reading to list
each of those words. Older adults consistently demonstrate poorer working memory than
younger adults (e.g., Bopp & Verhaeghen, 2005; Reuter-Lorenz & Sylvester, 2005).
While types of memory dependent upon procedural or fluid abilities are sensitive to age-
related decline, types of memory that depend on accumulated knowledge are relatively robust to
the effects of age. Memory for the contents of a person's cumulative general knowledge- not
requiring recollection of specific place, time, or context is referred to as semantic memory.
Verbal memory measures, such as vocabulary tests, are a common way of assessing semantic
memory. In a cross-sectional study evaluating several types of memory in age groups across the
adult lifespan, Park and colleagues (2002) demonstrated reduced performance with older age in
episodic memory, working memory, and short-term memory, but a stable profile for verbal or
semantic memory. Stable semantic memory ability with increasing age has also been reliably
demonstrated in other studies (e.g., Ronnlund et al., 2005; Allen et al., 2002).
The Utility of Story Memory Measures
Episodic memory can be assessed by recall of text passages such as short stories or
newspaper articles (Adams et al., 1990; Verhaeghen et al., 1993). Participants hear and recall
aloud a passage in which words and ideas follow a logical sequence, which then provides a
context for remembering. The story recall "gold standard" is Wechsler's Logical Memory test
(Wechsler, 1997), consisting of two short stories read aloud and immediately recalled aloud, and
recalled again after a 25-35 minute delay.
Story recall is an episodic memory measure relevant to real-life demands. It is more
ecologically valid to measure memory for a sequence of related events or ideas than, for
example, a list of words not united by any cohesive meaning. Daily life often requires memory
for short narratives (news events, word-of-mouth stories from friends), but rarely rote memory
for word lists. Additionally, story recall allows for the widely accepted notion that real-world
recall is rarely word-for-word, but instead usually abstracted, meaning it is often paraphrased and
gist- or main idea-based. Story memory measures offer an advantage by assessing these more
relevant styles of recall, word lists rely mostly on verbatim recall alone.
Age Differences in Story Recall
The maj ority of research on story recall in aging has focused on age differences. Older
adults consistently remember less story information overall compared to younger groups (Dixon
et al., 2004; Johnson, 2003; Verhaeghen et al., 1993; Pratt et al., 1989). Particularly, when older
adults are asked to memorize a story verbatim, they perform more poorly than younger adults
(Adams et al., 1997). However a recent review suggests that age differences vary depending on
whether verbatim- or gist-based memory (memory for main ideas, regardless of whether correct
wording is recalled) is required. A meta-analysis by Johnson (2003) found the nature of task
instructions and scoring guidelines affects the size of age differences such that age differences
were smaller in studies with scoring based on gist criteria rather than verbatim. Therefore scoring
guidelines emphasizing word-for-word recall, and recall for details, may be more sensitive to age
differences. On the other hand, schemes allowing paraphrasing of information and
summarization of main ideas may lead to relatively better memory performance in older adults.
Effect sizes of age differences are also much larger for word-list verbal memory measures
(Verhaeghen et al., 1993). These tests place greater emphasis on verbatim, text-based recall and
do not allow for synonyms, paraphrases, interpretation of meaning, or varying levels of
information, such as main ideas and secondary details.
Studies examining the content of information recalled main ideas versus details have
found that older adults tend to remember fewer details compared to younger peers. But, like
younger adults, elders demonstrate better recollection for main ideas than for secondary details.
The Victoria Longitudinal Study (Hultsch et al., 1998) that compared to younger age groups,
adults aged 74-84 showed poor recall for details at all testing occasions compared to younger
adults, but maintained a high level of recall for main ideas six years following baseline testing
(Dixon et al., 2004).
A recent study by Chapman and colleagues (2006) investigated older adults' performance
on three kinds of gist: memory for global generalized meaning of a passage, memory for main
ideas of a passage, and memory for categorical clustering of lists of words. This study found that
older adults' memory is poorer for semantic categories and for main ideas than for the global
generalized meaning of a passage. The age differences literature supports this finding. Older
adults recall less than younger adults when asked to literally retell a story, but outperform their
younger peers when asked to interpret the story (Adams et al., 1997). While younger adults excel
at text-based story reproduction, older adults are superior at integrating ideas and interpreting
story meaning (Adams, 1990). In addition to retelling and summarizing story content, they also
often provide more elaborations on the text and inferences from the story than younger adults,
including speculation on the psychological and metaphoric meanings of the passage (Adams,
1991). A cross-cultural study replicated these findings in Japanese older adults (Hosokawa,
Divided Attention in Aging
Regardless of age, performance on a task is known to decline when attention is divided
between that and performance of a second, simultaneous task (a dual-task challenge). Studies
have shown that this performance decline is also greater with increasing age (Albinet et al.,
2006; Holtzer et al., 2004; Chen, 2000).
However, this age difference has not consistently been found (e.g., Anderson et al., 1998;
Salthouse et al., 1995). The inconsistency of findings may be in part due to lack of understanding
about the underlying reason for differences when they are found. Alternative hypotheses argue
that a) older adults' reduced performance is due to reduced ability to perform concurrent tasks, b)
older adults' poorer performance is the result of general cognitive slowing, or c) the age
difference in dual-tasks is accounted for by different strategies used, with older adults perhaps
strategizing more cautiously (Meyer et al., 2001). A recent dual-task study found age
differences, maintained after adjusting for individual differences and generalized slowing, which
were suggestive of different strategies between the age groups (Rekkas, 2006). Another found
that providing strategy instructions reduced age differences (Naveh-Benj amin et al., 2005).
Riby and colleagues (2004) completed a comprehensive review of dual-task aging
research conducted between 1981 and 2003. They reported a strong overall effect of age-related
dual task impairment (d-.68), but the Eindings among individual studies varied. Subsequent
analyses revealed that one maj or reason for this was the failure to control for baseline
differences. This finding illustrated the value of investigating whether age differences are due to
specific dual-task difficulties or to a general decrement in performance. Somberg and Salthouse
(1982) purported that age differences in dual task performance would disappear if once baseline
differences were controlled for, suggesting dual task age differences were in fact the result of
general age-related decline. However, Riby and colleagues found studies that compared relative-
to-baseline measures of performance obtained larger effects for age-related dual-task costs than
studies that compared absolute measures of performance. These Eindings suggest that controlling
for baseline ability may isolate a true effect of dual-task challenge.
Additionally, this study found that age differences are smaller for verbal tasks and for
verbal reaction time responses than for visuospatial tasks. Perhaps because verbal tasks under
dual-task conditions have smaller age-related decrements, the role of age in verbal recall during
divided attention is somewhat unclear. Several dual-task studies using verbal recall report greater
reductions in recall for older adults during dual-task performance (Craik et al., 1998; Park et al.,
1989), but others report no age difference (Anderson et al., 1998; Nyberg et al., 1997).
The investigators found that the most critical factor associated with variability of Eindings
for dual-task age differences was the task domain used. Namely, simpler tasks or those requiring
relatively automatic processing were associated with smaller age-related performance deficits.
On the other hand, dual-task scenarios involving a motor component demonstrated larger age
differences in performance, such as walking and memorizing (Lindenberger et al., 2002). A
meta-analysis by Verhaeghen and colleagues (2003) expands the relationship between dual-task
age difference and task modality by reporting that matched-modality tasks produced reliably
larger dual-task costs than paradigms utilizing tasks from two different modalities. Other studies
have reported greater age-related dual-task deficits for explicit versus implicit memory (Light,
1991), and for performance of concurrent memory tasks (Salthouse, Rogan, & Prill, 1984),
versus performance of concurrent perceptual tasks (Somberg & Salthouse, 1982). Riby and
colleagues (2004) also observed larger age-related deficits in dual-task scenarios requiring a
substantial amount of effortful, controlled cognitive processing such as working memory,
episodic memory, and reasoning tasks.
Elders' Performance in Driving Divided Attention Tasks
The influence of automatic versus effortful tasks on the size of age differences in dual
tasks may have implications for the present study, which pairs verbal recall with the everyday
task of driving. While driving is a complex task involving the coordination of visual scanning,
attention, decision-making, and motor skills, it is also a relatively automatic, daily-practiced
behavior for most people. How, then, might older adults perform in a dual-task scenario in
which one of the concurrent activities is driving?
The first answer to this question and the most relevant to this paper is the finding from
Cook (2007), the primary analysis on the same dataset from which this paper is derived. Sarah
Cook evaluated older adults' lane navigation performance in a dual-task study of simulated
driving and story recall. She found that the addition of a concurrent story recall task had no
negative effect on participants' ability to maintain lane position; instead, they actually
demonstrated less lane deviation than in the single lane navigation task. One way to resolve
these counterintuitive Eindings is that participants may have prioritized the driving task due to the
real-world dangers distracted driving entails, and sacrificed the verbal recall task. This
explanation is supported by the finding that verbal recall overall did decline under dual-task
conditions, while lane navigation improved. Another piece of the explanation may be that
driving is a relatively automatic task, while episodic recall has been regarded as an effortful task.
It would then make sense for driving performance to be relatively preserved while recall
performance declines. However, the broader Eindings from similar studies have been varied.
Crook and colleagues (1993) compared different age groups across the adult life span on
the simultaneous performance of a verbal recall task and a computer-simulated driving reaction
time task. Participants in the older age groups demonstrated greater performance declines on
both the verbal and reaction time tasks in the dual-task scenario. After controlling for
psychomotor speed, older adults still demonstrated poorer reaction times, suggesting the dual-
task effect was due to cognitive rather than psychomotor factors. The greatest age differences
were observed between the youngest (18-39 yrs) and the oldest groups (70-85 years).
McPhee and colleagues (2004) found similar results in a concurrent task of visual search
for traffic signs and recall of the Wechsler Logical Memory stories. While all age groups
suffered dual-task performance costs, older adults demonstrated differentially greater dual-task
costs on both tasks. They recalled significantly less of the Logical Memory stories than younger
adults in the dual-task condition. They also were slower and less accurate in deciding when a
target sign was not present during dual-task conditions, especially in high-clutter scenes on the
visual search task.
However the findings on older adults' dual task performance of verbal tasks and
simulated driving, like the majority of dual-task literature, is also somewhat inconsistent. A
recent study evaluated the effect of verbal production and verbal comprehension on velocity and
lane position control during a computer driving simulation (Kubose et al., 2006). This study
found that while driving velocity became more variable during verbal production and
comprehension compared to driving alone, the concurrent production of speech while driving
actually yielded better lane position control, and verbal comprehension had no effect on lane
position control. Additionally, verbal production and comprehension performance were not
impacted by the added challenge of simultaneously driving.
Age Differences in Recall Under Divided Attention
The qualitative age differences in recall poorer verbatim memory and superior
integration in older adults appear to be consistent in dual-task scenarios, if not compounded by
the additional challenge of divided attention. Arbuckle and colleagues (1985) found that the level
of verbatim recall decreased in older adults with the addition of a simultaneous verbal task.
Compared to younger adults, they gave fewer verbatim responses and more inferences,
elaborations, and overgeneralizations, indicating that in the presence of a second simultaneous
task, the quality of older adults' recall again focuses on overall ideas more than on text
The Role of Mild Cognitive Impairment
Introduction to Amnestic Mild Cognitive Impairment
The previous sections have focused on changes in verbal recall and dual-task
performance in the context of normal, healthy aging. However the course of aging is varied, and
can deviate from the typical slow general decline of normal aging to the onset of Alzheimer's
Disease (AD) or other cognitive disorders, which become more prevalent with increasing age.
Cognitive aging exists on a continuum then, from healthy typical decline to mild impairment to
severe dementia (Petersen et al., 1999).
Mild Cognitive Impairment (MCI; Petersen et al., 1999) refers to the area in the middle
of the continuum, and has come to represent with some controversy a transitional zone
between normal age-related cognitive decline and the very early clinical stages of AD (Petersen,
2005). The MCI construct does serve as a clinically relevant predictor of progressing to
dementia (Lopez et al., 2003; Daly et al., 2000), and was endorsed as such in 2001 by the
American Academy of Neurology (Petersen et al., 2001). However, MCI does not consistently
predict progression to AD, and can even be associated with subsequent improvements in
cognition. Its presentation is sufficiently heterogeneous as to necessitate clinical
subclassifications (e.g. single domain impairment in memory or another domain, multiple
domain impairment). These different subclassifications may lead to a wide variety of outcomes,
and each is associated with a different set of possible prognoses. The subtypes are primarily
distinguished based on presence or absence of memory impairment, and are therefore
characterized as amnestic (aMCI) or non-amnestic MCI (Petersen, 2004).
This study focuses on patients of the aMCI subtype, which consists of a mild memory
impairment more pronounced than what is normally seen with advancing age (performance 1 1.5
SD below the norm for a patient' s age and education), accompanied by a subj ective memory
complaint. However cognitive function in other domains such as language and attention is
preserved, as are activities of daily living (ADLs; for example, grooming, bathing and feeding),
and these patients do not meet the clinical criteria for dementia.
Importantly, aMCI as a categorically-definable phenomenon is a somewhat artificial
construct. Much research has focused attention on whether MCI is truly a discrete entity,
distinguishable from normal cognitive aging and from dementia. The findings are thus far
inconclusive (Davis & Rockwood, 2004). But the difficulty of characterizing MCI as a discrete
phenomenon is intuitive. It underscores the notion that if cognitive aging does exist along a
continuum, then categorizing cognitive decline into stages is not faithful to its nature. Advocates
of establishing guidelines for identifying MCI as a distinct stage understand this issue, but
acknowledge that quantifiable performance cutoffs are inevitably necessary for MCI to be used
as a clinical entity. The diagnosis and treatment of progressive cognitive decline relies on
obj ective measurement of cognitive abilities, and cutoff points are made as precisely as can be
but could never be exact. One method that would be useful in assessing how cutoff points are
determined, and which neuropsychological measures are used to classify aMCI, is policy
capturing. Policy capturing is a method used by researchers to evaluate how individuals make
decisions (Karren & Barringer, 2002). It uses quantitative methods like cluster analysis,
discriminant functions, and logistic regression to evaluate the way individuals "weight, combine,
and integrate" available information to make a judgment. While this method is frequently used
on an organizational or societal level, in job searches and hiring analyses for example, it has
relevant implications for investigating the way researchers and clinicians formulate diagnoses of
MCI. Policy capturing analyses will be employed later in this document to identify the
underlying algorithm that seemed to guide the classifications decisions of our own study's
consensus conference judgments.
However, this reality does not negate the pragmatic value of developing and
implementing diagnostic criteria to identify MCI. Current clinical criteria have been shown to
predict progression to AD, albeit without perfect consistency to date. The additional
sophistication of the aMCI criteria has been argued to be a more sensitive predictor of AD
pathology, as 10-15% of patients move on to a diagnosis of AD each year, compared to 1-2 of
the general population (Petersen et al., 2001). An aMCI diagnosis has also been associated with
lower rates of survival (Leep Hunderfund et al., 2005).
Impact of Cognitive Impairment on Story Recall
Research indicates that declines in verbal episodic memory, including for paragraph
recall, are among the most commonly reported in older adults with aMCI or in the preclinical
stages of Alzheimer' s disease (Collie & Maruff, 2000, Kluger et al., 1999). But those with aMCI
retain intact activities of daily living, and therefore continue to drive. Because they are still
active and independent in daily life but experiencing early memory loss, these individuals may
be at greatest risk for forgetting episodic information crucial to their daily functioning, and may
be especially vulnerable to forgetting information if they are distracted by other simultaneous,
cognitively complex activities such as driving.
The story recall literature indicates that cognitively impaired individuals consistently
recall less overall than their healthy peers on stories (Gely-Nargeot et al., 2002; Robinson-
Whelen & Storandt, 1992) and on other verbal memory measures (Greenaway et al., 2006;
Balota et al, 1999). A study by Johnson and colleagues (2003) compared young adults, healthy
older adults, very mildly and mildly demented adults (AD) on measures of both verbatim and
gist-based recall for stories. The results of this investigation revealed there was a significant
effect of dementia among the older adults, such that very mildly and mildly demented older
adults remembered less story information verbatim, and less of the gist of the story, than healthy
older adults. The effect of dementia on recall was more severe for verbatim recall than for gist.
Another recent study by Hudon and colleagues (2006) specifically examined recall
content memory for the gist versus the details of a story and found that adults with MCI and
adults with AD recalled less of both the gist and details of a story, compared to healthy adults.
Additionally, they reported that even recognition of gist-level information is decreased in
individuals affected by greater impairment: they found that adults with AD showed additional
deficits in main idea recognition, while this ability was relatively spared in adults with MCI.
Similarly, Chapman and colleagues (2006) found that mildly impaired adults performed poorer
than healthy older adults on three types of gist memory: semantic categories for word-lists, main
ideas of a text passage, and global general meaning of a passage. This is in contrast to healthy
older adults, who demonstrate relatively preserved strength in memory for a story's global
meaning. It suggests that impaired adults' ability to integrate and interpret stories, which is a
strength in healthy older adults, is negatively impacted. Unsurprisingly, in addition to
remembering fewer main ideas and details and less overall meaning, impaired adults also show a
reduced ability to accurately recognize inferences (Bielak et al., 2007).
Impact of Cognitive Impairment on Dual-Task Performance
Research consistently indicates that compared to healthy older adults, the costs to
performance on dual-tasks are significantly larger for those in the early stages of Alzheimer' s
Disease. However the consistency of dual-task costs, as with normal aging compared to younger
adults, is also less clear for persons with MCI. Perry, Watson and Hodges (2000) reported no
differentially greater dual-task costs for MCI participants, but consistent impairment for mildly-
demented AD participants in dual-task performance and other areas of attention. Conversely, a
recent study (Belleville et al., 2007) found that persons with MCI exhibited impaired
performance on a divided attention task but preserved performance on other measures of
attention, while persons in the early clinical stages of AD exhibited impairments on all measures
of attention. Additionally, participants with MCI who demonstrated subsequent declines also
showed impaired attentional performance on tests of manipulation abilities compared to MCI
participants who did not decline.
As in the normal aging literature, it has been postulated that performance decrements at
lower levels of cognitive status are simply the reflection of decreased cognitive capacity and
processing speed, and there is no differential effect of divided attention per se. However, Holtzer
and colleagues (2004) corrected for age, education, and performance among groups of healthy
and cognitively impaired participants and continued to find reliably greater dual-task costs for
impaired participants. They also argued, based on the results of a discriminant function analysis,
that the dual-task measures were more accurate in discriminating impaired and healthy elders
than traditionally-used neuropsychological measures.
Similar to Riby and colleagues' (2004) findings in the normal aging literature, task
selection impacts the size of dual-task effects for cognitively impaired persons. Crossley and
collaborators (2004) demonstrated that dual-task scenarios requiring little effortful processing
may show no impairment-related dual-task costs, but tasks requiring effortful cognitive activity
may produce impairment-related costs. The study compared healthy participants and participants
with early-stage AD in performance on concurrent unimanual tapping and speaking tasks. When
speaking was relatively automatic (speech repetition), there was no discernable difference in
dual-task costs between groups. However when effortful speech was required (speech fluency),
cognitively impaired participants demonstrated larger dual-task costs than their healthy peers.
This overview of the research illustrates that in terms of story recall, older adults have a
poorer verbatim and detail-based memory compared to younger adults, but are superior at
summarizing story themes, interpreting meaning, and elaborating and making inferences upon
the story information. The findings on dual-task performance costs in elders are as yet unclear.
There have been reports of age differences associated with increased dual-task costs for older
adults, but these reports have not been consistent throughout the literature, and several theories
have been postulated to address this issue. Finally, the research on cognitive impairment
consistently reports that older adults with MCI demonstrate greater general reductions in story
recall; however the existing literature provides mixed reports on whether persons with MCI
exhibit larger dual-task costs than healthy older adults. The following chapter will discuss the
specific aims of this investigation.
STATEMENT OF THE PROBLEM
Episodic memory, or memory for specific events and experiences, is more strongly
affected by age-related cognitive decline than semantic memory, or memory for more general,
acquired information (Nyberg & Tulving, 1996; Tulving, 1995). Older adults report this change
in their everyday lives as more-frequent forgetting of acquaintances' names or details for recent
events. Additionally, dividing attention between two simultaneous tasks often reduces cognitive
performance. Older adults may be more prone to forgetting episodic information when they are
distracted by doing something else simultaneously, such as listening to the radio while driving.
Adults whose cognitive decline is greater than normal for age may be especially susceptible to
forgetfulness during distraction. If age-related episodic memory loss is compounded by the effect
of distraction, then older adults are at a greater risk for forgetting information conveyed to them
while driving (such as news bulletins, traffic warnings, or conversations with passengers).
Because important verbal information including verbally-conveyed directions, passenger or
cellular phone conversations, or radio news or alerts is often communicated to older adults
while driving, the risk of forgetting has important functional implications for cognitively healthy
and impaired adults alike.
The goal of this study was to investigate the effect of simultaneous simulated driving on
episodic memory performance, as measured by verbal recall of a brief news story. Driving and
story recall tasks were performed under three conditions: alone, under slow-speed dual-task
challenge (30 mph driving), and fast-speed dual-task challenge (60-mph driving). Sixty-one
community-dwelling older adults with and without memory impairments were asked to
participate. Story memory was evaluated in terms of precision, defined as verbatim (word-for-
word) versus paraphrase recall, and content, defined as recall for main ideas versus recall of
secondary details. There were three main goals of the study.
Dual-Task Effect on Precision
To understand the effect of dual-task driving and recall on story memory precision,
defined as verbatim and paraphrase. Recall for the number of "idea units" of the Rivermead story
paragraphs (Wilson et al, 1985) was compared across single-task, slow-speed dual-task, and fast-
speed dual-task conditions in terms of verbatim and paraphrase recall.
Story recall will decrease overall with increasing condition difficulty. As a proportion of
all possible idea units, verbatim recall will decrease more greatly than paraphrase recall.
Dual-Task Effect on Content
To understand the effect of dual-task driving and recall on story memory content, defined
as main ideas and details. Recall for the number of "idea units" of the Rivermead story
paragraphs was compared across single-task, slow-speed dual-task, and fast-speed dual-task
conditions in terms of recall for main ideas and details.
Overall, story recall will decrease with increasing condition difficulty. Recall for details,
as a proportion of the number of detail idea units possible, will decrease at a differentially greater
rate than recall for main ideas, quantified as the proportion recalled out of the total main idea
idea units possible.
Role of Cognitive Impairment in Dual-Task Effects on Precision and Content
To investigate the role of cognitive ability in story memory performance during dual-task
driving and recall. Recall across conditions was compared between healthy and cognitively-
impaired older adults in terms of verbatim versus paraphrase and main ideas versus details
Cognitively impaired adults will show lower levels of story recall than healthy adults in
all conditions. Additionally, impaired adults will demonstrate a greater decrease in performance
as task condition difficulty increases. Compared to healthy adults, impaired adults will
demonstrate a greater decline in verbatim and paraphrase recall with increasing condition
difficulty, and a greater decline for recall of details. No group differences are expected for recall
of main ideas across increasing condition difficulties.
RESEARCH DESIGN AND METHODS
Older adults were asked to recall short stories alone and under slow and fast dual-task
conditions while performing a simulated lane navigation task. They also completed
neuropsychological testing for the purpose of identifying possible memory impairment. A
consensus group met to determine cognitive status for all participants. The following sections
describe the relationship of the present study to the parent study (Cook, 2007), participants and
the selection process, study procedures and the measures used, and the design, procedures and
materials of the experimental task.
The Cook Study
This study was conducted as an extension of a study designed and initiated by Sarah Cook
(2007). The present study and parent studies shared the same overarching design and data set,
and were conducted in tandem. The author and Ms. Cook worked together to accomplish
participant recruitment, screening, and consensus classification. The author also completed
approximately half of the data collection, administering neuropsychological tests and conducting
the experimental protocol. The findings from the Cook study are summarized in the literature
The Cook study used total story recall scores to assess overall changes in recall associated
with the dual task challenge. The present study investigated beyond this general overview to
explore changes within various dimensions of recall (verbatim or paraphrased recall, recall of
main ideas). In order to do this, the author established additional scoring systems to evaluate the
precision and content of recall. Division of stories into individual idea units was used to provide
a detailed analysis. Two levels of scores (verbatim, paraphrase) were used to quantify recall
precision, and each idea unit was coded as a main idea or detail to quantify the content of recall.
Sixty-one community-dwelling older adults (age 65-91) were recruited from the
community. Efforts were aimed at recruiting both healthy older adults, and those with mild
memory impairments. Forty-six participants were classified as healthy or normal older adults,
and fifteen were classified as impaired, having been identified to have memory impairments.
Impaired participants received consensus classification of amnestic mild cognitive impairment
(aMCI) or dementia. The consensus classification process is described in the sections below.
Participants with a history of conditions or events that potentially disrupting normal
cognitive functioning were excluded. This includes adults with a history of epilepsy, head injury
with loss of consciousness, encephalitis, meningitis, Parkinson's disease, stroke within the last
year with residual motor signs, heart attack within the last year, and current cancer treatment or
past radiation treatment above the chest. Participants were also excluded who had never had a
driver s license or stopped driving more than 2 years ago. Participants with visual or auditory
impairments precluding valid testing (e.g. self-report of severe difficulty reading, or self report of
severe difficulty hearing in conversation) were also excluded. Participants were asked to identify
a friend or relative to who could serve as an informant for the purpose of the Clinical Dementia
Rating Scale (CDR).
Participants were recruited from several sources within the community, including
existing participant pools at the University of Florida (UF) National Older Driver Research and
Training Center (NODRTC) and Institute on Aging. Patients assessed at the UF Psychology
Clinic meeting study criteria were informed of the study by faculty, as well as patients at the UF
Memory and Cognitive Disorders Clinic, who were informed by a recruiting research team
member or whose information was released by UF's Clinical Alzheimer Program. A town hall
meeting was held for recruitment at a local continuing care retirement community, and
advertisements were made in local newspapers (The Gainesville Sun and The West End Journal).
In addition, two graduate student researchers studying similar patient groups provided participant
contact information for those interested in being contacted about future studies.
Participants were screened by telephone to exclude those who did not meet the inclusion
criteria stated above. Cognitive functioning was briefly assessed using the Modified Telephone
Interview for Cognitive Status (TICS-M; Brandt et al., 1988). This measure provides a
preliminary estimate of function and possible impairment with cutoff scores for MCI (<34) and
Administration of Neuropsychological and Experimental Tests
After giving informed consent, participants completed a neuropsychological assessment
and experimental task, which was completed during a single visit in one 3-hour block. The visit
was broken into 3 parts, each lasting approximately 1 hour (represented in Figure 3.1). First, a
primary neuropsychological battery was administered to assess cognitive status and other
possible factors contributing to task performance. Second the experimental task, described in the
following pages, was administered. Third, questionnaires and secondary neuropsychological
measures were administered as part of a larger study. Breaks were provided during the
experimental task and offered during neuropsychological testing as needed. Some participants
were recruited from another study using some of the same neuropsychological measures: the
Mini Mental Status Examination, the Hopkins Verbal Learning Test, and Useful Field of View.
One participant who had completed these measures within the past month consented to have his
data shared for the study. Those measures were not re-administered to him for this study.
Participants who had completed the other study more than one month ago were re-administered
the tests, taking into account the progressive nature of MCI and the importance of making the
most accurate possible classification.
A consensus conference panel consisting of the investigator, a neuropsychology faculty
member, a cognitive psychology member, and a neuropsychology student met at the conclusion
of data collection to identify participants with aMCI and early-stage AD. Assignment to a
cognitive impairment group was decided based upon cognitive performance and on ability to
carry out daily functions as reported on the Clinical Dementia rating scale. Neuropsychological
test results were reviewed in percentile format, with special attention given to participants whose
test scores ranked at or below the 7th percentile (according to the definition of impairment as 1.5
SD below the mean by Petersen et al., 1999). Each panel member individually identified
impaired participants before the list was reviewed and a vote was made for the status of each
participant identified by a panel member. If the vote was unanimous, the participant was
identified as impaired; if there was disagreement, the participant's performance and daily
functions were further discussed until a maj ority vote (3 out of 4) could be reached. After
consensus, the sample sizes of the two impaired groups were found to be much smaller than the
healthy sample. Consequently, a dichotomous (normal vs. impaired) conceptualization was used
for analyses of the results instead of the original three-group experimental design.
Telephone Screening Measure
To establish whether participants met inclusion criteria, they were asked several questions
about medical history and demographics. They also received the Modified Telephone Interview
for Cognitive Status (TICS-M; Brandt et al., 1988), a short measure designed to assess cognitive
ability in situations where in-person evaluation is inconvenient or impractical. It is similar to the
Mini-Mental Status Examination, but with a more extensive memory component and can be
administered over the telephone.
Neuropsychological Consensus Measures
To ensure that participants met criteria for inclusion in one of the 3 cognitive groups
(healthy, mild cognitive impairment, or probable dementia), we administered a battery of
measures assessing memory and other areas of cognitive functioning. The battery was chosen
based on measures identified by the Consortium to Establish a Registry for Alzheimer's Disease
(CERAD) to be useful in assessing for Alzheimer's disease and other dementias associated with
aging. The cognitive domains assessed were chosen in order to identify not only memory
impairment, a primary feature of dementia, but also to establish breadth and depth of impairment
across multiple areas of functioning. These domains were also selected in order to rule out
impairment based on primary deficits in areas other than memory, such as attention.
Global cognition. The Mini-Mental Status Exam (MMSE; Folstein et al., 1975) was
used to assess global cognition. The MMSE is a brief 30-point measure of orientation, memory,
language, attention, and visuospatial processing. These abilities were examined more in-depth
with other measures.
Verbal memory. Verbal memory was assessed using the Hopkins Verbal Learning Test
(HVLT; Brandt & Benedict., 2001) and the Wechsler Logical Memory subtest (Wechsler, 1997).
The HVLT is a list-memory task in which 12 semantically-related nouns are read aloud and
participants are asked to recall them. The list is repeated and recalled for 3 trials, and after a 25-
minute delay participants freely recall the list one more time. After the delayed recall, the test
includes a recognition task in which participants hear a list of words from the original list, new
but semantically related to the original list, or new and not semantically related. Participants are
asked to identify whether or not they recognize each word from the original list.
The Wechsler Logical Memory test is a paragraph-memory test in which a short story is
read aloud and participants are asked to recall it immediately after hearing it. Then a second
story is read twice, participants recalling the story each time after hearing it. Participants are
prompted to remember the story for a later time in testing. After a 25-35 minute delay,
participants are asked to recall each of the stories once more. Finally in a recognition trial,
participants are asked 15 yes-or-no questions about each story.
Language. Language was assessed using the Boston Naming Test (BNT; Kaplan et al.,
2001) and the Control Oral Word Association Test (COWAT; Benton & Hamsher, 1989). The
BNT measures the ability to name pictured obj ects; a 15-picture shortened version of the test was
established by CERAD for clinical testing and was used for this study. The COWAT is a
measure of verbal fluency in which participants are given one minute to generate as many words
as they can beginning with a particular letter. Three trials are given, each with a different target
letter. A fourth trial requires participants to name as many members of a category (e.g. animals)
as they can within one minute.
Processing speed. Processing speed was measured using the Trail Making Tests A and
B (Reitan, 1992), in which participants connect circles in a prescribed order as fast as they can.
This task requires visual scanning and sequencing, psychomotor speed, concentration, and
Visuospatial construction. Constructional ability was assessed using the Rey-Osterrieth
Complex Figure Copy task (Rey, 1941). The participant is shown a complex figure and asked to
copy it on a piece of paper. Scoring is based on both how accurately components of the figure
are drawn, and on how accurately those components are placed within the figure.
Attention. Attention was assessed with both the Wechsler Digit Span subtest (Wechsler,
1997) for verbal attention and the Ruff 2 & 7 Selective Attention Test (Ruff & Allen, 1996) for
selective attention. Digit Span consists of two parts in which participants are first read a string of
digits and asked to repeat them, and second are asked to repeat a string of digits in reverse order.
The Ruff Selective Attention test requires visual search and cancellation, assessing both
sustained and selective attention. It consists of twenty 15-second trials in which the participant is
asked to visually search lines of numbers, or lines of numbers and letters (there are 10 trials of
each type). Participants are to draw a line through the numbers 2 and 7. Scoring takes into
account both correct hits and errors of omission to calculate the tradeoff between speed and
Visual attention. Visual attention and processing speed, which decline with age and can
increase the difficulty of driving performance, was assessed using the Useful Field of View
(UFOV; Ball & Owsley, 1993. This computer-administered task measures sustained, selective,
and divided attention. The first subtest of the task requires identification of a centrally-presented
target (car or truck). The second subtest requires simultaneous identification of the centrally-
presented target and of the location of a peripherally-related target (car). The third subtest is
similar to the second but requires the peripheral target to be located amid visual clutter (triangles
across the visual display). A fourth subtest required participants to determine whether two
centrally presented targets were the same (two cars or two trucks) or different (car and truck), as
well as identifying the location of the peripheral target. Each subtest adapts to the participant's
performance such that the score is based on the fastest speed at which the participant is able to
identify 75% of stimuli accurately.
Working memory. Working memory was assessed using an auditory n-back task
including 1-back, 2-back and 3-back tests. For the 1-back task, participants hear a series of letters
over a sound file and are asked to indicate with a button press whether each letter they hear is the
same or different as the letter before it. Similarly, with the 2- and 3-back tasks, participants are
asked to indicate whether the current letter is the same or different as the letter presented 2 letters
ago or 3 letters ago, respectively. Scoring incorporated both accuracy and response time.
Mood. Mood was assessed with the Geriatric Depression Scale (GDS; Yesavage, 1983).
The GDS consists of 30 yes-or-no, self-report items about symptoms of depression common
among older adults. The GDS was included to account for any possible effect of depression on
participants' memory and attentional performance.
Daily function. The Clinical Dementia Rating Scale (CDR; Morris, 1993) was collected
as a measure of daily functioning for participants whose neuropsychological test results were
ambiguous regarding impairment. This measure was administered over the telephone after
testing. It included questions for both the participant and his or her designated informant about
memory, orientation, judgment and problem solving, home and hobbies, community affairs, and
basic self-care. Scores were based on an algorithm of the scores assigned for each of these
domains. A CDR score of 0 indicated no impairment, 0.5 indicated mild impairment, and 1.0
indicated moderate impairment.
The tests and specific scores used to measure each area of cognitive ability for the purpose
of consensus classification are described in Table 3-1.
The experimental task was administered after the primary neuropsychological battery and
before the secondary measures and questionnaires, and took approximately one hour to complete.
Participants first heard and, after a 35-second delay, recalled aloud three Rivermead short stories.
Stories were administered and recalled one at a time. All responses were recorded using a digital
recorder, and were later transcribed for scoring. After recalling three stories under single-task
conditions, participants completed a five-minute lane navigation acclimation task on the driving
simulator in order to become comfortable with operating the equipment. They completed two
short driving courses at 30 mph, the first consisting of all right-hand turns and the second of all
Following acclimation, the dual-task part of the experiment was administered in two
13.5-minute segments, with a 4.5 break period in between to prevent fatigue. Within each
segment three stories were administered concurrently with simulated lane navigation. Each story
was completed under slow or fast driving conditions (either 30 or 60 mph), and alternated such
that the three stories in segment one were given in slow-fast-slow conditions respectively, and
segment two stories were given as fast-slow-fast. Participants received a period of single-task
driving as a buffer between each story administration.
Participants listened to stories through a digital recording played over a speaker beside
the desktop. At the end of the story, the program instructed them to remember what they just
heard. After 35 seconds, participants were prompted to say aloud what they remembered. To
keep recall from overlapping with the beginning of the next driving condition, response time for
each story was limited to one minute.
An illustration of the experimental study procedure can be found in Figure 3-1.
Experimental Measures and Materials
Short story measures
Nine stories were administered altogether: three alone without simultaneous simulated
driving, three with simultaneous slow driving, and three with simultaneous fast driving. The nine
stories were divided into three groups of three, and each story group was randomly administered
in the alone segment, during the first dual-task segment, or during the second dual-task segment,
so that each participant heard each of the nine stories only once.
Four of the stories were from the Paragraph Recall Task of the Rivermead Behavioral
Memory Test (Wilson et al., 1985). The other five stories had been used in a memory training
study and were created using an algorithm created to make them to correspond directly to the
Rivermead paragraphs in complexity, structure, and number of idea units. The term "idea unit"
is used to refer to each individual lexical item within the story. For example, the following
sample sentence is divided into "idea units":
Ms. Virginia / Boone / a mother of two / won / the mother of the year award / on
Sunday / during a community celebration / in Chicago.
The complete text for all stories is included in Appendix A. For brevity, the Rivermead-type
paragraphs will be referred to as "Rivermead" stories throughout the rest of this document,
acknowledging that not all of them came from the actual Rivermead Behavioral Memory test.
Stories administered alone were read aloud by the testing technician. Stories in the dual-
task condition will be presented on the computer as a recorded male voice. After presentation
(about 45 seconds) participants were given 35 seconds to mentally rehearse the story before
recalling it aloud within a one-minute time limit. Participant responses were digitally recorded
and later transcribed.
Short story scoring
Stories were scored for precision based on the accuracy and completeness of recall. Each
idea unit was scored as 0 (not recalled), 0.5 (paraphrase or incompletely recalled), or 1 point
(verbatim or completely recalled). This scoring method was based on the system already
developed for the Rivermead paragraphs, and adapted also for the algorithm-generated stories.
Stories were also scored for recall content, or how much of recall consists of main ideas and
how much of it consists of supporting details. Idea units were coded as either main idea or detail
information, based on a consensus process. Investigators initially met with language and
discourse experts to evaluate what criteria existed for coding main idea and detail phrases. Given
that no validated method was found, investigators recruited ten college-educated individuals to
code each story. Idea units identified as a main idea by five or more consensus members were
considered main ideas for the purposes of the study; all other idea units were considered
Precision and content were quantified as the percent of idea units recalled out of the total
possible. So in the case of precision, because all idea units could be recalled either verbatim or in
paraphrase, verbatim recall was calculated as the number of idea units recalled verbatim out of
21 possible idea units. Likewise, paraphrase recall was calculated as number of idea units
recalled in paraphrase out of 21. Main idea recall was calculated as the proportion of main idea
idea units recalled out of the number of main ideas possible, which varied for each story. Recall
of details was similarly calculated as the number of detail idea units recalled out of the number
possible within each story. Figures 3-3 and 3-4 depict the formulas used to derive these
proportional recall scores.
To ensure reliability, two independent raters scored all story recall responses, and the
average of these two rating was used in all analyses. An analysis of inter-rater reliability was
conducted by correlating the two score sets. Ratings provided by each of the two raters were
positively correlated for each story administered in each condition (ranging from r=0.93 to
r=0.97, p<.001). Story recall ratings can therefore be interpreted as reliable.
STISIM Drive software was used for creation and administration of the simulated lane
navigation task. Scenarios were presented on a Dell Optiplex GX270 desktop computer (rather
than a driving simulator due to the high probability of simulator sickness in older adults), with a
19-inch flat screen monitor and Logitech MOMO Force Feedback Steering Wheel. The steering
wheel was attached to a desk in front of the computer, and participants were seated at the desk
with the monitor approximately 18 inches away.
The task involved simulated driving on a two-lane roadway consisting of right and left
turns and varying curve angles. There were no traffic lights or signals, and no other vehicles or
pedestrians on the road. The terrain to either side of the road was flat and void of any objects,
and there was a fixed view of a mountain range in the landscape up ahead. Figure 3.4 depicts a
screen shot typical of the driving scenario. Participants were instructed to drive in the right-hand
lane as they would on a normal road, and to do their best to maintain their lane position through
the curves and through the changes in driving speed.
(using serial 7 subtraction)
Total Immediate, Delay, and
Total Immediate, Delay, and
Total (F, A, S)
Time for A, Time for B,
Errors for A, Errors for B
Forward Span and Backward
Accuracy, Controlled Search
Table 3-1. Measures used for consensus classification.
Variables of Interest
Brandt et al.,
Morris et al.,
Ruff & Allen,
Interview for Cognitive
Mini-Mental Status Exam
Hopkins Verbal Learning
Wechsler Memory Scale-
Third Edition Logical
Boston Naming Test 15-item
CERAD version (BNT-15)
Control Oral Word
Trail Making Test A and B
(Trails A, Trails B)
Wechsler Adult Intelligence
Test- Third Edition, Digit
Ruff 2 & 7 Selective
Geriatric Depression Scale
Clinical Dementia Rating
Greeting, Study Administer Primary
Consent, and Battery and
Payment Paperwork: Questionnaires:
10-20 minutes 60 minutes
Figure 3-1. Participant visit overview. Participants are introduced to the study for 10-20
minutes. They next complete the primary neuropsychological battery, which takes
approximately 60 minutes. They then complete the experimental task, lasting 60
minutes, and finish the remainder of the neuropsychological battery after the
ISlow Fast Slowl
Dual Task Segment 1
Note: S = one story unit; Administered alone = single-task condition; Slow = slow-
speed dual-task condition; Fast = fast-speed dual-task condition.
Figure 3-2. Experiment procedures represented by task condition. The experimental task was
divided into three segments, each consisting of three story administrations. In the
first segment, three stories were recalled without the simultaneous driving task. In
the second and third segments, participants completed the story recall and driving
tasks simultaneously, alternating between low and high levels of speed for each story.
IAdministered alone I
Single Task Segment
IFast Slow Fast
Dual Task Segment 2
21 (All possible propositions)
Total propositions recalled
ParanhrasedPP~~PP~~~PP~~PP Recall =
21 (All possible propositions)
Figure 3-3. Calculation of verbatim and paraphrased recall scores
Total "main idea"
MainIdeaRecal =propositions recalled
All possible "main idea" propositions
(varies with story)
All possible "detail" propositions
(varies with story)
Figure 3-4. Calculation of main idea and detail recall scores
This study investigated recall of short stories in older adults aged 65 and older, whose
cognitive status ranged from normal to memory impaired. We examined how the addition of a
secondary task condition (simulated lane navigation) affected the style of older adults' recall,
under two levels of secondary task difficulty (slow speed of 30 mph and high speed, 60 mph).
We also investigated whether the effect of distraction by a secondary task would be similar for
healthy and impaired participants.
The study addressed three main experimental hypotheses. First, we aimed to confirm that
both verbatim and paraphrased recall would decrease as a function of increasing task difficulty,
and verbatim recall would decrease more than paraphrased recall. Second, we aimed to confirm
that recall for both main ideas and details would decrease with increasing task difficulty, and that
this decrease would be greater for recall of details than for main ideas. Third, we sought to
determine whether these changes in recall quality (verbatim, paraphrase) and content (main
ideas, details) would be disproportionately greater for impaired versus healthy participants.
Preliminary questions were explored regarding the reliability and validity of the story
recall measure. We expected scores to be reliable among stories administered in the same
condition. To assess the validity of the stories, we investigated whether total recall scores on
stories administered in the single-task condition were consistently related to total immediate
recall scores obtained on the Wechsler Memory Scale (WMS) Logical Memory paragraphs.
Preliminary analyses also evaluated the effect of the secondary driving task on total recall
scores. Setting the specific dimensions of recall (precision and content) aside, adding a
simultaneous secondary task was expected to decrease story recall overall. Also, to verify that
participants identified as memory-impaired truly differed from those classified as cognitively
healthy, preliminary analyses were conducted to identify overall recall differences between the
groups on the memory task.
Because all assessments for each participant were completed within a single session,
there was no participant dropout. There was, however, missing experimental (driving and
remembering) data because some participants were unable to complete the experimental task due
to sickness associated with the driving simulator task. Although four of the participants
completed part of the driving task, eight participants were unable to complete any of the dual-
task condition stories, and were excluded from analyses for this reason. Two of these eight were
classified as impaired. Because analyses were based on the average percent recalled within each
condition, participants who completed at least one story recall in each condition were included in
the analyses (with their averages computed from those stories they did manage to recall).
Seventeen participants completed at least one story in each condition, but discontinued the
experimental task after the end of the first dual-task segment. Reasons for discontinuation
included fatigue, complaints of dizziness from driving, or excessive frustration with the task.
Table 4-1 contains information on the number of participants with complete, partial, or no data.
To evaluate the validity of the Rivermead measures, we tested them against the Logical
Memory component of the Wechsler Memory Scale (WMS), a widely-validated measure of
immediate verbal short story recall. Every participant in the study recalled three Rivermead
stories in the absence of distraction. Every participant also completed both of the WMS Logical
Memory short stories without distraction, as part of the neuropsychological battery used for
consensus classification. It was expected that if the Rivermeads are a valid measure of short
story memory, participants' mean total recall on the Rivermead stories in the distraction-free
condition would positively correlate with the Total Immediate Recall score on Logical Memory
(Trial One on Stories A and B). Analyses using Pearson bivariate correlations revealed that
averaged Rivermead scores correlated significantly with Logical Memory recall scores, r=.672,
p<.001. This comparison may be interpreted as supportive evidence of the Rivermead stories'
validity relative to the story recall gold standard, with the caveat that the relationship is only
moderate. It was not possible to directly compare participants' percentile ranking on the
Rivermead-type and Logical Memory stories, since such percentile data did not exist for many of
the Rivermead-type stories.
If the Rivermead measures are reliable, it is expected that total recall scores of stories
administered within the same task condition should positively correlate with one another. We
conducted correlational analyses among story scores within each condition, and found that
stories were well-correlated within the single-task condition (r=.62-.69, p<.001), the slow dual-
task condition (r=.49-.62, p<.001), and the fast dual-task condition (r=.64-.71, p<.001). These
findings may be interpreted as evidence that the Rivermead stories are a reliable measure of short
Dual-Task Effect on Total Recall
Before looking at qualitative characteristics within story recall, we aimed to verify the
impact of task difficulty (i.e. addition of a secondary task, at two levels of challenge) on overall
memory performance. This question was investigated as part of the primary data analysis
conducted by Cook (2007). It was hypothesized that with increasing levels of task difficulty,
total recall scores would decline. A repeated-measures analysis of variance (RM-ANOVA)
revealed that memory performance did decrease significantly with each greater level of task
difficulty (F(2, 102)=19.36, p<.001). Paired-samples t-tests were then used to compare recall
among each of the three difficulty levels (single task, slow dual task, fast dual task). Compared
to the single task scenario, memory performance was significantly reduced in the slow dual-task
(p<.001) and fast dual-task (p<.001) conditions. If Bonferroni-corrected, the critical level of
alpha would be .017; thus, these comparisons remain significant even after correction. However,
there was no significant decline in memory performance between the slow and fast conditions
within the dual-task scenario.
Overall Memory Performance between Cognitive Status Groups
To verify that the groups identified as cognitively healthy and cognitively impaired
differed on memory performance overall, a one-way ANOVA was conducted comparing total
story recall scores between each of the groups across all task conditions (N=41 healthy, 12
impaired). Mauchly's test of sphericity was violated; therefore Greenhouse-Geisser corrections
were used. This analysis revealed significant differences between the groups' recall scores in
every condition, F(1,5 1)=16.3 8, p<.001, r,2=.24 The means and standard errors of each
group's total recall score in each condition are illustrated in Table 4-2. These findings were also
part of the primary data analysis conducted by Cook (2007).
Aim One: Dual-Task Effect on Precision
A repeated measures analyses of variance (RM-ANOVA) was conducted to examine the
effect of task condition on recall precision, defined as information recalled verbatim versus
information recalled in paraphrase (N=53). The dependent variable for the first analysis was
defined as the proportion of idea units recalled out of the 21 possible, averaged across the 3
stories within each condition. We used the 2-level independent variable of recall precision
(verbatim, paraphrase), and the 3-level independent variable of condition (single-task, slow dual-
task, fast dual-task). This analysis revealed a significant two-way interaction, F(2,104)=11.32,
p<.001, r,2=.28. Verbatim recall was consistently higher than paraphrased, but with increasing
task condition difficulty the proportion of idea units recalled verbatim decreased at a
differentially greater rate than the proportion recalled in paraphrase. In fact, the proportion of
idea units recalled in paraphrase did not change across any level of task difficulty. Post hoc
analyses (least squares difference) revealed that while verbatim recall dropped significantly with
each higher level of task difficulty (p=.001-.015; significant after Bonferroni correction,
oc=.017)., paraphrase recall did not differ among any of the levels of difficulty. These results are
illustrated in Figure 4-1.
Aim Two: Dual-Task Effect on Content
A repeated measures analyses of variance (RM-ANOVA) was conducted to examine the
effect of task condition on recall content, defined as main idea recall versus recall for details
(N=53). This analysis used recall as the dependent variable, this time defined in terms of the
average proportion of either main idea or detail idea units recalled out of the number possible
within each story. As with the first analysis, this proportion was then averaged across all stories
given within the same condition. The 2-level independent variable of recall content defined as
main ideas and details was used, as well as the 3-level independent variable of task condition as
defined above. There was no significant interaction in this analysis. However, there was a
significant main effect of content, F(1,104) = 380. 17, p<.001, r,2=.88. with the proportion of
recall for main ideas being consistently higher than the proportion of recall for details. There was
also a main effect of condition, F(2,104) = 17.55, p<.001, r,2=.25, with overall decreasing recall
with increasing task difficulty.
Post hoc comparisons revealed that recall for main ideas was significantly reduced in the
fast dual-task condition compared to the single-task and slow dual-task conditions; however, the
increase in difficulty between the single and slow dual-task had no effect on main idea recall.
(p=.001-.021; significant after Bonferroni correction, a=.017). Additionally, post hoc analyses
showed that detail recall was significantly reduced in the slow and fast dual-task conditions
relative to the single-task condition, but did not differ between the two dual-task conditions
(p<.001; significant after Bonferroni correction, a=.017). In other words, main idea recall was
most reduced at the highest level of difficulty, and detail recall was most reduced when the
secondary task was introduced and was not further reduced by increasing difficulty in the
secondary task. The results of this analysis are illustrated in Figure 4-2.
Aim Three: Role of Cognitive Impairment in the Dual-Task Effects
The two dimensions of recall, precision and content, were combined in a 3x2x4 RM-
ANOVA to examine the within-subj ects effect of task condition (single, slow dual-task, high
dual-task), and the added between-subj ects effect of cognitive status (healthy, N=41; impaired,
N=12), on overall recall style. Precision and content were combined to create 4 levels of the
independent variable recall style, defined idea units called verbatim, idea units recalled in
paraphrase, main idea idea units recalled, and detail idea units recalled. Recall for each category
was calculated as a proportion of the idea units recalled out of all the idea units possible within
each story. A significant three-way (task condition, cognitive status, recall style) interaction was
obtained (F(6,3 06)=2.62, p=. 03 7, r,2=.049). The results of this interaction are illustrated
separately for each dimension of recall (verbatim, paraphrase, main ideas, details) in Figures 4-3
To better understand the interaction, this analysis was further decomposed into two
separate 3x2x2 RM-ANOVAs evaluating the effect of impairment on recall precision and
content individually. The first RM-ANOVA explored the effect of condition (single-task, slow
dual-task, fast dual-task) and cognitive status (healthy, N=41; impaired, N=12) on recall
precision (verbatim, paraphrase). There was a significant two-way interaction of precision and
condition F(2,102)=6.43, p=.002, r,2=. 11, as seen in the analyses for Hypothesis 1, but the
three-way interaction was not significant, indicating recall did not vary by impairment.
Least Squares Difference post hoc comparisons indicated that the cognitive status groups
differed significantly on verbatim recall at every level of task difficulty, with impaired adults
consistently recalling less information word-for-word than healthy adults (p=.001-.003); these
comparisons sustained significance after Bonferroni correction using critical a level of
.017. However at the paraphrase level of recall, there was no difference between the two groups
at any difficulty level, and in fact there was also no difference for paraphrase recall within either
group among any levels of difficulty. There were differences in verbatim recall within each
group related to task condition, such that healthy adults demonstrated a decline in recall at every
increasing level of difficulty (p=.016-.018, significant after Bonferroni correction, a=.017).
Impaired adults, on the other hand, showed a more gradual decline: while verbatim recall
steadily decreased across conditions, a statistically significant difference was obtained only
between the single-task and fast dual-task levels of difficulty. The results of this analysis are
illustrated separately for healthy and impaired subj ects in Figures 4-7 and 4-8.
The second 3x2x2 RM- ANOVA explored the effect of condition (single-task, slow dual-
task, fast dual-task) and cognitive status (healthy, N=41; impaired, N=12) on recall content
(main ideas, secondary ideas). Mauchly's test of sphericity was violated; therefore Greenhouse-
Geisser corrections were used. The three-way interaction was not significant, but a significant
two-way interaction was obtained for content and cognitive status, F(1,51)=5.38, p=.024,
r,2=.095. This suggests again that the effect of task difficulty on recall performance does not
vary by cognitive status. Both groups demonstrated higher recall for main ideas than for details,
but the difference between main ideas and details recalled was larger for healthy participants
than for the impaired. Although it did not contribute significantly to the interaction, there was a
main effect of condition, F(2,102)=9.98, p<.001, r1,2=.16, with recall decreasing overall as a
function of increasing condition difficulty.
Least Squares Differences post hoc analyses showed that the cognitive status groups
differed at every difficulty level for detail recall, with impaired participants recalling fewer
details in each condition (p=.001-.046); these comparisons would have sustained significance
after Bonferroni correction using a critical a level of .017. Regarding main idea recall, impaired
participants recalled less information than healthy participants in the single-task and slow dual-
task conditions only; in the fast dual-task condition, the two groups performed equally.
Within-group post hoc comparisons revealed that there was no effect of task difficulty on
main idea recall within the impaired group, but the healthy group demonstrated a significant
decline in main idea recall during the fast dual-task condition (p=.001; this would have held
significance under Bonferroni correction, a=.017). In terms of details recall, the impaired group
showed a steady but slight decline in performance such that only the single-task and fast dual-
task conditions reflected significantly different levels of recall. The healthy group demonstrated
a significant reduction in detail recall between the single-task and slow dual-task conditions, but
performance did not continue to decline between the slow and fast dual-task conditions.
The results of this analysis are illustrated separately for healthy and impaired adults in
Figures 4-9 and 4-10.
Policy Capturing and Cognitive Status Classification
Policy capturing, a method used to evaluate how individuals make decisions, lends insight
for this study in understanding the process employed to classify cognitive status groups. The
present study relied substantially on the decision-making of the consensus conference to conduct
its analyses. Participants were classified into healthy and impaired cognitive groups based on the
collective decision of the neuropsychological consensus panel. The neuropsychological data
from all measures was available to the panel, represented as scaled or T scores and percentile
ranks. However, decisions about a participant' s cognitive status were made in accordance with
the most up-to-date criteria for MCI classification. That is, special attention was given to
measures of memory, such as the Hopkins Verbal Learning Test (HVLT) and Wechsler' s
Logical Memory Scales. It was scores of <1.5 SD below the mean score on these measures that
were used to make assignments of amnestic MCI.
To verify the consistency of the panel's classification, policy capturing analyses were
conducted on the assignment of cognitive status groups. A single discriminant function was
extracted to separate the two groups. This function had a canonical correlation of 0.90 with
group membership, suggesting that the function was strongly predictive of normal-vs.-MCI
classification. Congruently, the function was significantly predictive of group membership
(h=. 19, X2(5)=83 .91, r,2=. 81, p <.001).
Standardized canonical discriminant function coefficients (which assess the unique
contribution of each predictor, controlling for others in the model) were used to identify the
relative salience of our variables for predicting group membership. The loadings (L) [note to
Shannon...put each of these "L" s in italics] were as follows: HVLT Percent Retention percentile,
L = .68; UFOV Same/Diff, L= -.51; HVLT Recognition Index T Score, L=.44; HVLT Delayed
Recall T Score, L= .38; and Digit Span percentile, L= .33. Consistent with prediction, three of
the variables are HVLT-based (i.e., verbal memory), with a particular emphasis on variables that
should be lower in amnestic MCI (i.e., impaired delayed recall and reduced ability to profit from
retrieval support via recognition). The other two variables (Useful Field of View and Digit
Span) are somewhat less central to the amnestic MCI definition. This may either have reflected
the idea that the consensus panel used additional expertise regarding concepts that might aid in
classification, or that these other measures were correlated with MCI group membership,
reflecting the onset of more global decline processes associated with incipient dementia. In any
event, the results suggest that while there were elements of policy capturing (four of the five
variables reflected some component of memory), group assignments did not seem to be based on
a single one or two variables.
The discriminant function analysis achieved a high degree of sensitivity and specificity in
the classification of participants. Overall, 60 out of 61 participants were classified correctly
(98.4%). Sensitivity was 100% (15 out of 15 persons with MCI were correctly identified by the
function), and specificity was 97.8% (45 out of 46 unimpaired individuals were correctly
classified). Leave-one-out cross-validation was further explored to assess generalization of the
classification efficiency to the larger population. Here, akin to the jackknifing procedure,
classification was examined in N resamples from the data set, with each resample leaving out one
participant and reexamining the discriminant function classifications for that reduced sample.
The results of the leave-one-out cross-validation suggested that, identically to the sample-
specific results, 100% of persons with MCI were correctly classified and 97.8% of persons
without MCI were correctly classified.
Thus, given high measures of association between the discriminant function and group
membership, and high classification accuracy, the results suggest that the obtained discriminant
function did an excellent j ob of capturing the underlying policies that, de facto, governed case
Related to the question of policy capturing is the controversy of using a cutoff point,
namely 1.5 SD below the mean or 7th percentile of a distribution, to extract two groups from a
continuous distribution. Differentiating two groups out of performances which operate along a
continuum is difficult to defend unless the distribution of scores is bimodal. Importantly, one of
the memory-based predictors identified using discriminant function analysis, the HVLT Delayed
Recall scores, does have a bimodal distribution, as illustrated in Figure 6-1 in Appendix B. Other
variables which emerged as important in the discriminant function analysis did not have visibly
identifiable bimodal distribution. Participants' scores on the maj ority of other
neuropsychological measures were normally distributed, as reflected in Table B-1 skewnesss and
kurtosis estimates were generally non-significant, with the exceptions of scores on the TICS and
the UFOV Processing Speed and Selective Attention subtests. Performance on these measures
typically "ceilings" in healthy adults, causing the distribution of scores to be positively skewed
rather than bell-shaped).. This underlies the fact that cognition generally operates along a
continuum, and that groups based on neuropsychological performance represent opposite sides of
a cutoff point in that continuum, rather than discriminable groups. This issue will be discussed
further in the Discussion chapter.
Proportionalized Scoring Relative to Baseline Performance
Reviews of the dual-task literature indicate that discrepancies among findings have
historically been due to inconsistencies in controlling for baseline differences. Therefore, we ran
an additional set of analyses to address this question in our own dataset. Because the only
between-groups comparison was made for Aim 3 (healthy participants versus cognitively
impaired), a follow-up analysis was conducted solely for this question. Baseline differences
were controlled by dividing each participant's score in each condition (single-task, slow dual
task, fast dual task) by his or her score in the single task condition.
Two 3x2x2 (condition by precision by impairment, N= 53; condition by content by
impairment, N=53) repeated measures analyses of variance were conducted in the same format
as the original analyses conducted separately for precision and content in Aim 3; the only
difference for these follow-ups was the use of recall scores adjusted for baseline differences as
described above instead of absolute recall. The first RM-ANOVA revealed that when using
relative-to-baseline scores as the dependent variable, no significant interaction was obtained for
condition by precision by impairment. The second RM-ANOVA similarly identified that there
was no significant interaction of condition by content by precision using relative-to-baseline
scores. Although the results of these analyses were not significant, they are represented as
additional data in Figures 6.1-6.4 in the Appendix C.
Dual Task Slow Dual Task Fast
Figure 4-1. Proportion of idea units recalled verbatim or in paraphrase across task conditions
(N=53). Verbatim recall is consistently higher than paraphrase in all conditions, and
decreases at a significantly greater rate with increasing task condition difficulty. The
proportion of information recalled in paraphrase remains relatively stable. Total
recall (not shown) would be equal to the sum of verbatim and paraphrase recall, as
shown. Error bars represent the 95% confidence interval of the mean.
Table 4-1. Number of participants with complete, partial or no data by cognitive status.
Complete Data 38 9
Partial Data 3 3
No Data 5 3
Total 46 15
Table 4-2. Means + standard errors of story recall total scores
impaired participants (N=12).
Cognitive Status Group Single-Task Slow Dual-Task
Healthy 8.98 1 .37 7.36 + .41
Im aired 5.63 + .67 4.81 +..54
by healthy (N=41) versus
7.47 + .41
4.29 + .75
0 Main Ideas
Single Task Dual Task Slow Dual Task Fast
Figure 4-2. Proportion of main idea units recalled and proportion of detail idea units recalled
across task conditions (N=53). Recall for main ideas is consistently higher than recall
for details, and both types of recall decrease at equal rates with increasing task
difficulty. Total recall would be equal to the sum of main ideas and details recalled.
Error bars represent the 95% confidence interval of the mean.
Single Task Dual Task Slow Dual Task Fast
Figure 4-3. Proportion of verbatim recall in healthy (N=41) versus impaired (N=12) participants
recall across task conditions. The impaired group demonstrated less verbatim recall
than the healthy participants in each condition. There was no interaction between
cognitive status and task condition. Error bars represent the 95% confidence interval
of the mean.
Dual Task Slow
Figure 4-4. Proportion of paraphrased recall in healthy (N=41) versus impaired (N=12)
participants across task conditions. Paraphrased recall did not differ between groups,
and did not change across conditions. Error bars represent the 95% confidence
interval of the mean.
Single Task Dual Task Slow
Dual Task Fast
Figure 4-5. Proportion of recall for main ideas in healthy (N=41) versus impaired (N=1 2)
participants ideas across task conditions. Post hoc comparisons revealed the impaired
group recalled significantly fewer main ideas than healthy adults. There was no
significant cognitive status-task condition interaction. Error bars represent the 95%
confidence interval of the mean.
Dual Task Fast
p O Healthy
Single Task Dual Task Slow Dual Task Fast
Figure 4-6. Proportion of recall for details in healthy (N=41) versus impaired (N=12)
participants across task conditions. No significant interaction was observed between
cognitive status and task condition. Error bars represent the 95% confidence interval
of the mean.
p ~ I I II I I O Verbatim
Dual Task Slow Dual Task Fast
Figure 4-7. Healthy participants' proportions of verbatim and paraphrased recall across task
conditions (N=41). Verbatim recall decreased across conditions, while paraphrased
recall remained stable. Total recall would be equal to the sum of verbatim and
paraphrased recall. Error bars represent the 95% confidence interval of the mean.
Single Task Dual Task Slow Dual Task Fast
Figure 4-8. Impaired participants' proportions of verbatim and paraphrased recall across task
conditions (N=12). Paraphrase recall remained stable, while verbatim recall declined
slightly with increasing task difficulty. Total recall would be equal to the sum of
verbatim and paraphrased recall. Error bars represent the 95% confidence interval of
FI 0.0.6 nO M ain Ideas
Single Task Dual Task Slow Dual Task Fast
Figure 4-9. Healthy participants' recall for the proportion of main ideas versus details across
conditions (N=41). Recall for main ideas declined steadily with increasing task
difficulty, while detail recall remained stable. Total recall would be equal to the sum
of main ideas and details recalled. Error bars represent the 95% confidence interval
of the mean.
0 Main Ideas
Dual Task Slow Dual Task Fast
Figure 4-10. Impaired participants' recall for proportion of main ideas versus details across
conditions (N=12). Recall for main ideas remained stable, while recall for details
declined slightly across conditions. Total recall would be equal to the sum of the main
ideas and details recalled. Error bars represent the 95% confidence interval of the
This study examined the effect of a simultaneous secondary task, simulated lane
navigation, on two dimensions of story recall in older adults. One dimension was the precision of
recall, in terms of the proportion of information remembered either verbatim or in paraphrase.
The other dimension was the content of recall, in terms of the proportion of main idea
information recalled versus the proportion of detail information. The within-subj ects variable of
task difficulty was examined under three conditions: story recall alone, story recall in the
presence of a slow-speed simultaneous driving task, and story recall in the presence of a fast-
speed simultaneous driving task. Cognitive status (specifically, cognitively healthy versus
memory impaired) was investigated as a between-subj ects variable. The study evaluated the
effects of task difficulty and cognitive status, separately and in interaction, on the precision and
content dimensions of story recall.
Preliminary analyses examined the reliability and validity of the story recall measure.
Results revealed that the Rivermead stories are a reliable measure of story recall: paragraphs
administered within the same condition correlated positively with one another. Results also
indicated that the Rivermead stories are also comparable to a widely-validated test of story
recall, the Wechsler Logical Memory Scales: total immediate recall scores on both measures,
administered under single-task conditions, were positively correlated.
The remainder of this chapter will address the findings in regard to the study's three
specific aims. Next, the theoretical and practical implications of the results will be considered.
Finally, we will discuss the study's limitations, as well as possible future directions for this
Review of Findings
Aim One: Dual-Task Effect on Precision
The first aim of this study was to evaluate the effect of simultaneous simulated driving on
the precision of story memory in terms of verbatim versus paraphrase recall. It was hypothesized
that both types of recall would decrease with increasing condition difficulty, but that the decline
would be greater for verbatim recall than for paraphrased recall. The analyses revealed that
increasing levels of task difficulty were associated with decreasing levels of verbatim recall, but
had no significant effect on the proportion of paraphrased recall. But Post-hoc analyses showed
that the effect of task difficulty decreased verbatim recall across all conditions, and had no effect
on paraphrased recall for any condition. Additionally, participants consistently demonstrated
higher levels of verbatim than paraphrased recall.
These results are essentially in support of the hypothesis: the ability to recall information
word-for-word is vulnerable to increasing demand on attentional resources, and more so than the
ability to paraphrase information. However, it had been hypothesized that paraphrased recall
would also decline with task difficulty, albeit at a smaller grade than verbatim recall. The total
lack of effect of task difficulty on paraphrased recall suggests this ability is more resistant to
increasing cognitive load.
This indication should be interpreted with consideration, though, for the fact that
participants relied predominantly on a verbatim style of recall, which was their instructed goal.
The proportion of paraphrased recall was low across all conditions, ranging from 15% in the
single-task condition to 14% in the two dual-task conditions. This is a small proportion and range
compared to verbatim recall, which was 73% in the single-task condition, 65% in slow speed
dual-task, and 55% in the fast-speed dual-task condition. It may be that in a population instructed
to paraphrase, the proportion and range of paraphrased recall may be more sensitive to changes
in attentional demand.
Aim Two: Dual-Task Effect on Content
The second aim of the study was to examine the effect of simultaneous simulated driving
on the content of story memory in terms of recall for main ideas versus details. It was
hypothesized that while recall would decline overall as condition difficulty escalated, this decline
would be stronger for detail recall than for main ideas. Results indicated that recall did generally
decrease as the task condition became more difficult; however, the diminishing effect on recall
was equivalent for main ideas and details. Post hoc analyses further indicated that detail recall
decreased only between the single- and slow dual-task conditions, but decreased across all
conditions for main ideas.
One reason for participants' memory for details to be preserved in the face of increasing
task difficulty may be primacy and recency effects. These phenomena, well known in the
memory literature, refer to the higher frequency of recall for the first and last items in a list or
story. That is, primacy and recency effects may cause participants to be more likely to remember
the beginning and end of a story, regardless of whether it is main idea or detail information. In
the nine stories used for this study, 83% of the first and last two idea units consisted of detail
information. If memory for first and last information is also more resistant to increasing
attentional demand, participants were more likely to continue recalling the detail information
contained at the beginning and end of each story.
Additionally, recall for main ideas was higher than for details across all conditions. This
suggests that although memory for main ideas may be more sensitive to cognitive load than
memory for details, participants were nonetheless likely to remember more of the key points and
themes of the story than to remember its details.
Aim Three: Role of Cognitive Impairment in Dual-Task Effects
The third aim of the study was to evaluate the interaction of cognitive status (healthy
versus memory impaired) with the dual-task effect of simultaneous simulated driving on story
recall. It was hypothesized that participants with compromised cognitive status would
demonstrate lower levels of recall overall, but in addition, they would show greater costs to
memory performance associated with increasing task difficulty. Precision of recall (verbatim,
paraphrase) in impaired participants was hypothesized to show differentially greater decrements
in both verbatim and paraphrase recall compared to their healthy peers. For recall content (main
ideas, details), impaired participants were hypothesized to show a greater decrease in recall for
details as condition difficulty increased, but recall for main ideas was expected to remain
Results demonstrated that impaired participants consistently remembered less overall
compared to healthy participants, and that higher levels of task difficulty consistently reduced
recall for both groups. However, there was no interactive effect between cognitive status and task
difficulty; in other words, being memory-impaired did not amplify the cost to memory
performance created by increasing levels of challenge. At first glance, it seems counterintuitive
for impaired participants to handle increasing demands similarly to their healthy peers; the
impact of dividing attention between two tasks would seemingly be more taxing for a person
whose cognitive capacity is compromised.
However, the reason for this apparent disparity is likely explained by the match between
the type of cognitive task required and the type of impairment studied. In this study, task
difficulty was defined as single- versus dual-task, which was further subcategorized in two levels
of secondary task speed. Adding a second task requires participants to divide their attention
between two simultaneous activities, which increases the burden on attentional resources but not
on memory capacity. Participants for the impairment group were selected based specifically on
amnestic impairment. Their performance on the memory task supports their classification; they
consistently demonstrate poorer memory than their healthy peers. However their impairment is
primarily in the memory domain and not necessarily in attention. This is supported by the
observation that they perform similarly to healthy participants in terms of coping with greater
attentional load. So while we hypothesized a differential effect of divided attention for impaired
participants, they in fact perform exactly as we should expect: they demonstrate consistently
poorer memory, but in the presence of increasing attentional burden, they demonstrate the same
costs to performance as their healthy peers.
Analyses of group differences within precision of recall (verbatim vs. paraphrase)
revealed that verbatim recall in both groups was equally reduced, while paraphrase recall was not
affected by task difficulty in either group. Recall of main ideas was not significantly affected by
task difficulty for either group, but recall for details decreased significantly for each group with
increasing task difficulty. This cost to performance was equivalent for both healthy and impaired
participants. So again, no interaction was observed between cognitive status and task difficulty.
But within the dimension of recall precision, there was also no effect of difficulty on paraphrase
recall for either group only on verbatim recall. Additionally within the dimension of recall
content, there was no effect of difficulty on recall for main ideas for either group only for
details. This suggests that while memory impairment does not amplify the effect of task
difficulty, task difficulty itself has a negative effect for both groups on the capacity for verbatim
recall and for recall of details. Both results are consistent with what would be expected, given
that these types of recall are typically more demanding of memory than paraphrase recall and
recall for main ideas.
The findings from Aims 1 and 2 illustrate the impact of divided attention on verbal
memory performance for older adults in general. Our results suggest that when older adults are
required to listen to and remember verbally-conveyed information while driving, their ability to
recall that information may be substantially degraded by the additional challenge of driving. In
particular, older adults may experience a reduced ability to remember verbal information
precisely, and may recall less of the content, both in terms of main idea- and detail-level
information. Older adults may experience these difficulties more strongly if the verbal
information is conveyed under especially challenging driving conditions.
Aim 3 demonstrates the impact of divided attention on memory-impaired older adults'
story recall, as compared to their healthy peers. Our findings suggest that impaired adults are
more vulnerable to forgetting verbally-conveyed information than those who are cognitively
healthy. Our findings also indicate that impaired adults experience lowered verbal memory
performance when their attention is divided between remembering and driving; however this
reduction is comparable to that experienced by healthy older adults. Therefore, although
impaired older adults show a reduced capacity for remembering verbal information, they are at
no greater risk for forgetting while distracted by driving than are their healthy peers.
The study possesses several possible limitations. First, as mentioned in the literature
review, smaller age differences are found in dual-task studies employing a relatively automatic
task. For many people, driving is a task learned at a young age and practiced almost daily
throughout the life span. While at its initial learning it may be an effortful coordination of
cognitive processes involving motor coordination, visual attention, and time-sensitive decision-
making, it is also an activity that becomes relatively automatic for most people as a result of
Second, even if driving is an adequately effortful task, the simulated driving task did not
fully emulate the complexity of real-world driving. Participants had no gas or brake pedals and
so were unable to adjust their speed as they normally would when navigating sharp curves.
Additionally, little visual scanning was required because the landscape was flat and unchanging.
Because the only challenge was then to stay within the right lane, the task was far simpler than
the complex task of driving in the real world, where numerous cognitive processes occur
simultaneously. Such limitations are common to controlled experiments: to evaluate a real-life
situation, it must sometimes be simplified in order to be accessible to meaningful analysis.
Third, the method used to classify cognitive status may have played into the absence of a
condition-by-impairment interaction. While the memory measure most used to discriminate
between groups appeared to be bimodal, the maj ority of cognitive measures were normally and
continuously distributed. Cognition, and cognitive decline in aging, operate along a continuum.
The division of participants into groups based on a cutoff is an imprecise conceptualization of
cognitive function, and may have led to a loss of interaction effect that would have surfaced if
cognition were used as a continuous variable. On the other hand this classification, if somewhat
untrue to the nature of cognition, is also necessary for the sake of dissemination for public use.
While the point at which cognitive impairment begins is not yet well-defined and certainly not
discrete, cognitive impairment itself is nonetheless a real phenomenon with important
implications for those who experience it. Classification systems are intrinsic to the application
of research findings in clinical diagnostics and treatment; as it is, they are also rarely without
flaws. In the case of MCI, it involves the classifying individuals on opposite sides of a dividing
line in distributions that do not actually consist of two separate groups. It also reflects, as seen in
this study's simplified policy capturing analysis, that while cognition has many dimensions
which are represented by many measures, only a handful of measures are typically actually used
in the process of classification.
A fourth limitation that could have confounded recall performance is the issue of
interference among stories. Participants heard nine short stories within a relatively brief time
period, so there is reasonable risk of information from one story becoming mixed up in another.
Because the stories were written based on an algorithm, several contained similar items of
information such as the story's location, time of day, and character's first and last names. For
example, participants sometimes would describe one story's events as having happened "last
night", even if this phrase was not part of the story and instead had been heard in a previous
Other limitations include the sample population and size. The study sample consisted
mostly of highly-educated Caucasian older adults, which is not representative of the broader
senior population. The advantage of high education may have led to better performance and
possibly different learning strategies in the sample compared to the general population.
Additionally, the size of the cognitively impaired group was smaller than was needed for
adequate statistical power. The obtained group differences may have demonstrated greater
significance had there been a larger group of impaired participants.
One clearly useful next step for the present study would be to match the cognitive
demand of the experimental task to the type of cognitive deficit in the population studied. In this
study the cognitive demand manipulated was related to attention, but the population studied was
memory-impaired. It appears that despite the fact that a recall task was involved in this
experiment, a better way to observe differential dual-task effects in an impaired population may
be to more systematically manipulate the cognitive burden that is directly related to the
population in question. For example, a similar future study may vary the difficulty of the
memory task in a dual-task scenario instead of increasing driving difficulty, or may choose to
pair a verbal memory with a visual memory test. Such a study should also aim to recruit larger
samples of cognitively impaired participants, allowing enough statistical power for group
differences to be detected.
Additionally, cognitive status group differences in dual-tasks or simply age differences
in general may be more readily detected by a scenario employing two tasks within the same
modality. As it was mentioned in the literature, same-modality tasks typically yield larger age
differences, likely because of greater competition for the same cognitive resources. This study
used an auditory story memory task and a visual-motor navigation task, requiring dual-task
performance from two different, non-competing modalities. Such experiments have typically
been shown to have smaller age differences in dual task performance costs, so perhaps a bigger
effect would emerge if tasks using the same modality were performed.
Looking at the driving portion of the experiment, another future direction may be to
manipulate the automaticity of this task. As the literature indicated, dual tasks employing
relatively automatic cognitive processing such as driving often yield smaller performance costs
than those requiring effortful processing. The level of effort required for this task could be
increased by incorporating other aspects of the driving experience (e.g., use of brake pedals,
varied terrain, participant-controlled speed), or perhaps by increasing the difficulty of the driving
scenario. These kinds of changes to the driving component would have the added benefit of
increasing the ecological validity of the task. Similar changes could be made to improve the
relevance of the verbal task, such as carrying a conversation (or some other experimental task of
speech production and comprehension) while driving.
Anecdotally, participants often approached the dual-task challenge by stating they
intended to ignore the memory task and focus on driving, since that's what they would do if a
news story were on in the car. This occurrence underscores the potential future issue of
manipulating attentional allocation, which was not controlled in this study. A more thorough
future study might systematically evaluate the effect of attention allocation by emphasizing that
participants first prioritize the driving task and sacrifice the story recall, then prioritize the story
recall and sacrifice the driving.
Finally, other qualitative aspects of recall could be more deeply explored. Because it was
a verbal recall task, responses often contained irrelevant utterances that may be related to lapses
in memory or attention. Such utterances include um's, ah's, and verbalizations not directly related
to the story, such as comments on the difficulty of the task or unsolicited opinions on the story
content. Such information is not typically coded in story recall scores, but is nevertheless useful
in understanding the style and quality of responses. This kind of data can be especially
informative in comparative studies involving the cognitively impaired.
This study evaluated the precision and content of story recall as affected by memory
impairment and by the addition of a simultaneous simulated driving task at both slow and fast
speeds. As we hypothesized, overall recall was reduced in the presence of increasing difficulty
within the task condition. Verbatim but not paraphrased recall decreased with greater task
difficulty, and recall for both main ideas and details decreased at the same rate with increasing
task difficulty. Memory impairment was associated with lower overall recall, but impaired
individuals demonstrated similar task difficulty-related performance costs when compared to
healthy individuals. Maj or limitations of the study the small sample size of the impaired group,
leading to insufficient power to detect potential group differences, potential over-simplification
of the secondary task, which reduces ecological validity, and the classification of continuously
distributed variables to create cognitive status groups.
This study's findings have valuable implications for the everyday life of older adults.
Important information is often conveyed during the everyday activity of driving. This can
include driving directions given over a cellular phone, radio traffic alerts, and information
conveyed in passenger conversation. When potentially important information is presented
verbally to older adults while they are simultaneously driving, their ability to retain this
information may be substantially degraded. Specifically, the precision of their recollection, as
well as their memory for details of the information, declines. As the difficulty of the driving
challenge increases, older drivers may additionally recall less of the main points of the
information conveyed. This study also demonstrates that for mildly memory impaired older
adults, the risks of forgetting verbal information while driving also apply, but are no greater for
persons with mild memory impairment than for those who are cognitively healthy.
SHORT STORIES USED INT THE EXPERIMENTAL TASK
Ms. Virginia / Boone / a mother of two / won / the mother of the year award / on Sunday / during
a community celebration / in Chicago. / The nominating committee/ of Chicago-Cares / hosted
the event / in the flower-decorated / Grace Cathedral. / News reporters / were a large presence /
at the event. / A church representative said, / "She is an amazing lady. / She raised those kids / in
a rough neighborhood / without a dime of help from anyone."
A Dutch / oil tanker / sank / ten miles / off the Norfolk coast / last night. / The crew / were
picked up / by a coast guard patrol boat. / An oil slick / is already forming / and conservationists
/ are worried / about the effects / on wildlife. / Local enthusiasts / are mounting an operation / to
save / any birds / found stranded / on the beaches.
Adam / Aubrey / a Nobel prize winner / was kidnapped / from his home / during a surprising /
terrorist attack / in Zurich / yesterday. / The attackers / were all hooded / and were said / to be
fleeing / in a private plane. / Swiss representatives / were seeking clues. / A US embassy /
representative said, / "We take this very seriously. / He is an international treasure / and we will
bring him back home.
Nicolette / Zabrinsky / a Red Cross / volunteer / was infected / with a viral disease / during a
blood bank / drive / in Los Angeles / last March. / An accidental slip / while trying to adjust / an
intravenous needle / caused the problem. / Disease control experts / were tying to contain / the
spread of the virus. / She is highly infectious now, / which is sad. / She was just trying / to help
Firemen / and volunteers / worked all day / yesterday / putting out / a bush fire / six miles / south
/ of San Diego / in southern California. / Fire engines / were unable to reach the area / so
firefighting equipment / was brought in by helicopter. / Livestock / was evacuated / from the
neighboring / Johnson's Farm / as it was engulfed / in clouds / of dense white smoke.
Mr. Brian / Kelly / a Pinkerton employee / was shot dead / on Monday / during a bank robbery /
in Atlantic City. / The four robbers / all wore masks / and one carried / a sawed-off / shotgun. /
Police detectives / were sifting through / eyewitness accounts / last night. / A police spokesman
said, / "He was a very brave man. / He went for / the armed robber / and put up a hell of a fight."
Two hundred men / at a shipyard / in New Jersey / went on strike / this morning. / The men
walked out / over a dispute / concerning fifty / lay-offs. / The shop steward, / Mr. Thomas / told
reporters, / "It is outrageous! / The company has full-order books / for the next two years." / A
management spokesperson said, / "We are hoping to begin / fresh negotiations / at main office /
Joellen / Reese, / a kindergarten pupil, / shocked spectators / with a performance / of
Beethoven's Fifth Symphony / last night. / She was inspired / by a piano / at Garden Place Mall./
Mall-goers / were astounded / by the beautiful music. / Said one mother, / "I was amazed / that a
little girl like that / could play / so well. / The piano / just seemed / to take her over."
Mr. Luther / Nathanson, / a Chrysler employee, / was injured / on the job / at a plant / in Toledo.
/ The assembly line / stopped suddenly / causing a large / car bumper / to hit his chest. / Plant
safety officers / were trying to understand / the problem / last night. / A company spokesperson
said, / "He's been a great worker. / We're looking forward to / a speedy recovery / and return to
DISTRIBUTIONS OF NEUROPSYCHOLOGICAL DATA
Table B-1. Skewness and kurtosis (N=61) of neuropsychological data distributions by measure.
Illustrates that scores on most measures are fairly normally distributed, without
intrinsic evidence of bimodality.
HVLT Trial 1-3 %tile
HVLT Delayed Recall T Score
HVLT Percent Retention Percentile
HVLT Recognition Index Percentile
WMS LM Trial 1 Total Scaled Score
WMS LM Stories 1 Total Scaled Score
WMS LM Story B Learning Scaled Score
WMS LM Stories 2 Total Scaled Score
WMS LM Percent Retention Scaled Score
COWA Fluency FAS Total Scaled Score
Category Animals Total Percentile
BNT Total Score Percentile
Rey-Osterrieth Copy Percentile
Trails A Time Scaled Score
Trails B Time Scaled Score
Digit Span Scaled Score
Ruff Automatic Speed T Score
Ruff Continuous Speed T Score
Ruff Total Speed T Score
Ruff Total Accuracy T Score
UFOV Processing Speed
UFOV Divided Attention
UFOV Selective Attention
Kurtosis Kur tosis
Mean =54 03
Std Dev =33 32
0 20 40 60 80 100
HVLT Delayed Recall %tile
Figure B-1. Histogram representing the frequency distribution of percentile scores for Delayed
Recall on the Hopkins Verbal Learning Test, the primary predictor of cognitive status
group as detected by discriminant function analysis.
0.6 -o- Helthy
Single Task Dual Task Slow Dual Task Fast
FOLLOW-UP ANALYSES USING SCORES RELATIVE TO BASELINE PERFORMANCE
Figure C-2. Comparison of idea units recalled verbatim by healthy (N=41) versus impaired
participants (N=12) across task conditions. Scores are represented as relative to
baseline; this was accomplished by dividing each participant' s score over their score
at baseline. Error bars represent the 95% confidence interval of the mean.
Dual Task Slow
Dual Task Fast
Figure C-3. Comparison of idea units recalled in paraphrase by healthy (N=41) versus impaired
participants (N=12) across task conditions. Scores are represented as relative to
baseline; this was accomplished by dividing each participant' s score over their score
at baseline. Error bars represent the 95% confidence interval of the mean.
0.8 -o Healthy
Single Task Dual Task Slow Dual Task Fast
Single Task Dual Task Slow Dual Task Fast
Figure C-4. Comparison of main idea units recalled verbatim by healthy (N=41) versus
impaired participants (N=12) across task conditions. Scores are represented as
relative to baseline; this was accomplished by dividing each participant' s score over
their score at baseline. Error bars represent the 95% confidence interval of the mean.
Figure C-5. Comparison of detail idea units recalled verbatim by healthy (N=41) versus
impaired participants (N=12) across task conditions. Scores are represented as
relative to baseline; this was accomplished by dividing each participant' s score over
their score at baseline. Error bars represent the 95% confidence interval of the mean.
LIST OF REFERENCES
Adams, C. (1991). Qualitative age differences in memory for text: A life-span
developmental perspective. Psychology and Aging. 6(3), 323-336.
Adams, C., Labouvie-Vief, G., Hobart, K., & Dorosz, M. (1990). Adult age group
differences in recall for the literal and interpretive meanings of narrative text.
Journal of Gerontology: Psychological Sciences, 45(1), Pl7-P27.
Adams, C., Smith, M., Nyquist, L., & Perlmutter, M. (1997). Adult age-group
differences in recall for the literal and interpretive meanings of narrative text.
Journal of Gerontology: Psychological Sciences, 4, 187-195.
Albinet, C., Tomporowski, P.D., Beasman, K. (2006). Aging and concurrent task performance:
Cognitive demand and motor control. Educational Gerontology, 32(9), 689-706.
Allen, P. A., Sliwinski, M., Bowie, T., Madden, D. J. (2002). Differential age effects in semantic
and episodic memory. Journal of Gerontology: Psychological Sciences, 57B, 173-186.
Anderson, N. D., Craik, F. I. M., & Naveh-Benj amin, M. (1998). The attentional demands
of encoding and retrieval in younger and older adults: I. Evidence from divided
attention costs. Psychology and A ing. 13, 405-423.
Arbuckle, T., & Harsany, M. (1985). Adult age differences in recall of a moral dilemma under
intentional, incidental and dual task instructions. ExperimentalAging Research, 11(3-4),
Baddeley, A. D. (1986). Working memory. Oxford: Clarendon Press.
Ball, K., & Owsley, C. (1993). The Useful Field of View Test: A new technique for evaluating
age-related declines in visual function. Journal of the American Optometric Association,
Balota, D. A., Cortese, M. J., Duchek, J. M., Adams, D., Roediger III, H. L., McDermott,
K. B., & Yerys, B. E. (1999). Veridical and false memories in healthy older adults and
in dementia of the Alzheimer's type. Cognitive Neuropsychology, 16, 361-384.
Belleville, S., Chertkow, H., & Gauthier, S. (2007). Working memory and control of
attention in persons with Alzheimer's disease and mild cognitive impairment.
Neuropsychology, 21, 458-469.
Benton, A., & Hamsher, K. (1989). Multilingual aphasia examination. Iowa City: AJA
Bielak, A. A. M., Hulstch, D. F., Kadlec, H., & Strauss, E. (2007). Was that part of the
story or did I just think so? Age and cognitive status differences in inference and
story recognition. Experimental Aging Research, 33(3), 295-322.
Bopp, K. L., & Verhaeghen, P. (2005). Aging and verbal memory span: A meta-analysis.
Journal of Gerontology: Psychological Sciences, 60B, 223-233.
Brandt, J. & Benedict, R. H. B. (2001). Hopkins Verbal Learning Test- Revised: Professional
manual. Odessa, FL: Psychological Assessment Resources.
Brandt, J., Spencer, M., & Folstein, M. (1988). The Telephone Interview for Cognitive Status.
Neuropsychiatry, Neuropsychology, and Behavioral Neurology, 1, 111-117.
Chapman, S. B., Anand, R., Sparks, G., & Cullum, C. M. (2006). Gist distinctions in
healthy cognitive aging versus mild Alzheimer' s disease. Brain napairnzent, 7(3),
Chapman, S. B., Zientz, J., Weiner, M., Rosenberg, R., Frawley, W., & Burns, M. H. (2002).
Discourse changes in early Alzheimer disease, mild cognitive impairment, and normal
aging. Alzheimer Disease and Associated Disorders, 16(3), 177-186.
Chen, J. Y. (2000). The effects of aging on dual-task performance: A meta-analysis of studies
between 1981 and 1997. Brain and Cognition, 44, 94-97.
Collette, F., Van der Linden, M., & Salmon, E. (1999). Executive dysfunction in
Alzheimer's disease. Cortex, 35, 57-72.
Collie, A., & Maruff, P. (2000). The neuropsychology of preclinical Alzheimer's disease
and mild cognitive impairment. Neuroscience and Biobehavioral Reviews, 24(3),
Cook, S. (2007). The impact of distraction on simulated lane navigation in older adults 11 ithr and
as without cognitive inspairnzent. Unpublished dissertation, University of Florida,
Craik, F. I. M, Naveh-Benjamin, M., & Anderson, N. D. (1998). Encoding and retrieval
processes: Similarities and differences. In M. A. Conway, S. E. Gathercole, & C.
Cornoldi (Eds.), Theories of mentory H (pp. 61-86). Hillsdale, NJ: Erlbaum.
Crook, T. H., West. R. L., & Larrabee, G. J. (1993). The driving-reaction time test
assessing age declines in dual-task performance. Developmental
Neuropsychology, 9(1), 31-39.
Crossley, M., Hiscock, M., & Foreman, J. B. (2004). Dual-task performance in early
stage dementia: Differential effects for automatized and effortful processing.
Journal of Clinical and Experimental Neuropsychology, 26(3), 332-346.
Daly, E., Zaitchik, D., & Copeland, M. (2000). Predicting conversion to Alzheimer
disease using standardized clinical information. Archives ofNeurology, 57, 675-
Dixon, R. A., Wahlin, A., Maitland, S. B., Hultsch, D. F., Hertzog, C., & Backman, L.
(2004). Episodic memory change in late adulthood: Generalizability across
samples and performance indices. Memory and' Cognition, 32(5), 768-778.
Fisk, J. E., & Sharp, C. A. (2004). Age-related impairment in executive functioning: Updating
inhibition, shifting, and access. Journal of Clinical and Experimental Neuropsychology,
Folstein, M. F., Folstein, S. E., & McHugh, P. R. (1975). "Mini-Mental State": A practical
method for grading the cognitive state of patients for the clinician. Journal of Psychiatric
Research, 12, 189-198.
Gely-Nargeot, M. C., Ska, B., & Touchon, J. (2002). Text structure and content
modulate the recall of patients with dementia of the Alzheimer' s type. Brain and'
Cognition, 48(2-3), 371-375.
Greenaway, M. C., Lacritz, L. H., Binegar, D., Weiner, M. F., Lipton, A., & Cullum, C. M.
(2006). Patterns of verbal memory performance in mild cognitive impairment,
Alzheimer disease, and normal aging. Cognitive and'Behavioral Neurology, 19(2), 79-
Head, D. P. I. (2002). The role of executive functions in age difference in episodic
memory. Dissertation Abstracts International: Section B: The Sciences and Engineering,
Head, D., Buckner, R. L., Shimony, J. S., Williams, L. E., Akbudak, E., Conturo, T. E.,
McAvoy, M., Morris, J. C., & Snyder, A.Z. (2004). Differential vulnerability of anterior
white matter in nondemented aging with minimal accelerationin dementia of the
Alzheimer type: evidence from diffusion tensor imaging. Cerebral Cortex, 14, 410-423.
Holtzer, R., Burright, R. G. & Donnovick, P. J. (2004). The sensitivity of dual-task performance
to cognitive status in aging. Journal of the International Neuropsychological Society, 10,
Hosokawa, A., & Hosokawa, T. (2006). Cross-cultural study on age-group differences
in the recall of the literal and interpretive meanings of narrative text. Japanese
Psychological Research, 48(2), 77-90.
Hudon, C., Belleville, S., Souchay, C., Gely-Nargeot, M. C., Chertkow, H., & Gauthier,
S. (2006). Memory for gist and detail information in Alzheimer' s disease and
mild cognitive impairment. Neuropsychology, 20(5), 566-577.
Hultsch, D. F., Hertzog, C., Dixon, R. A., & Small, B. J. (1998). M~enory change in the
aged. Cambridge, UK: Cambridge University Press.
Johnson, D. K., Storandt, M., & Balota, D. A. (2003). Discourse analysis of logical
memory recall in normal aging and in dementia of the Alzheimer type.
Neuropsychology, 17(1), 82-92.
Johnson, R. (2003). Aging and the remembering of text. DevelopnzentalReview, 23,
Kaplan, E. F., Goodglass, H., & Weintraub, S. (2001). The Boston Naming Test. (2 ed.)
Baltimore, MD: Lippincott.
Karren, R.J. & Barringer, M.W. (2002). A review and analysis of the policy-capturing
methodology in organizational research: Guidelines for research and practice.
Or ganizational Research M~ethods, 5(4), 3 37-3 87.
Kluger, A., Ferris, S. H., & Golomb, J. (1999). Neuropsychological prediction of decline to
dementia in nondemented elderly. Journal of Geriatric Psychiatry and Neurology, 12(4),
Kubose, T. T., Bock, K., Dell, G. S., Garnsey, S. M., Kramer, A. F., & Mayhugh, J. (2006). The
effects of speech production and speech comprehension on simulated driving
performance. Applied Cognitive Psychology, 20, 43-63.
Leep Hunderfund, A. N., Leibson, C. L., & Slusser, T. C. (2005). Survival in mild
cognitive impairment. Neurology, 64(Suppl. 1), Al66.
Light, L. L. (1991). Memory and aging: four hypotheses in search of data. Annual
Review ofPsychology, 42, 333-376.
Lindenberger, U., Marsiske, M., & Baltes, P. B. (2000). Memorizing while walking: Increase in
dual-task costs from young adulthood to old age. Psychology and Aging. 15(3), 417-436.
Lopez, O. L., Jagust, W. J., & DeKosky, S. T. (2003). Prevalence and classification of
mild cognitive impairment in the cardiovascular health study cognition study.
Archives ofNeurology, 60, 1385-1389.
Lovden, M. (2003). The episodic memory and inhibition accounts of age-related increases in
false memories: A consistency check. Journal of~entory and Language, 49, 268-283.
McPhee, L. C., Scialfa, C. T., Dennis, W. M., Ho, G, & Caird, J. K. (2004). Age
differences in visual search for traffic signs during a simulated conversation.
Human Factors, 46(4), 674-685.
Meyer, D. E., Glass, J. M., Mueller, S. T., Seymour, T. L., & Kieras., D. E. (2001).
Executive-process interactional control: A unified computational theory for
answering 20 questions (and more) about cognitive ageing. European Journal of
Cognitive Psychology, 13(1-2), 123-164.
Morris, J. C. (1993). The Clinical Dementia Rating (CDR): Current version and scoring rules.
Neurology, 43, 2412-2414.
Morris, J. C., Heyman, A., & Mohs, R. C. (1989). The Consortium to Establish a Registry for
Alzheimer' s Disease (CERAD). Part I. Clinical and neuropsychological assessment of
Alzheimer's disease. Neurology, 39, 1159-1165.
Mosley, M., Bammer, R. L., & Illes, J. (2002). Diffusion-tensor imaging of cognitive
performance. Brain and Cognition, 50, 396-413.
Naveh-Benjamin, M., Craik, F. I. M, Guez, J. & Kreuger, S. (2005). Divided attention in
younger and older adults: Effects of strategy and relatedness on memory
performance and secondary task costs. Journal ofExperintental Psychology:
Lea(lrnin. M~entory, and' Cognition, 31(3), 520-537.
Nyberg, L., Lars-Goran, N., Olofsson, U. (1997). Effects of division of attention during
encoding and retrieval on age differences in episodic memory. ExperintentalAging
Research, 23(2), 137-143.
Nyberg, L., & Tulving, E. (1996). Classifying human long-term memory: Evidence from
converging dissociations. European Journal of Cognitive Psychology, 8(2), 163-183.
Park, D. C., Lautenschlager, G., Hedden, T., Davidson, N. S., Smith, A. D., & Smith, P.K.
(2002). Models of visuospatial and verbal memory across the adult life span.
Psychology and A ing. 17, 299-3 20.
Park, D. C., Smith, A. D., Dudley, W. N., & Lafronza, V. N. (1989). Effects of age and a
divided attention task presented during encoding and retrieval on memory.
Journal ofExperintental Psychology: Lea-l~rning. Mentory, and' Cognition, 15(6),
Perry, R. J. & Hodges, J. R. (1999). Attention and executive deficits in Alzheimer's
disease: A critical review. Brain, 122, 383-404.
Perry, R. J., Watson, P., & Hodges, J. R. (2000). The nature and staging of attention
dysfunction in early (minimal and mild) Alzheimer's disease: relationship to
episodic and semantic memory impairment. Neuropsychologia, 38, 252-271.
Petersen, R. C. (2004). Mild cognitive impairment as a diagnostic entity. Journal of
Internal Medicine, 256, 183-194.
Petersen, R. C. (2005). Mild cognitive impairment: where are we? Alzheimer 's Disease
and Associated Disorders, 19(3), 166-169.
Petersen, R. C., Doody, R., Kurz, A., Mohs, R. C., Morris, J. C., Rabins, P. V., Ritchie, K.,
Rossor, M., Thal, L., & Winblad, B. (2001). Current concepts in mild cognitive
impairment. Archives ofNeurology, 58, 1985-1992.
Petersen, R. C., Smith, G. E., Waring, S. C., Ivnik, R. J., Tangalos, E. G., & Kokmen, E. (1999).
Mild cognitive impairment: Clinical characterization and outcome. Archives of
Neurology, 56, 303-308.
Pratt, M. C., & Lombardi, L. (1990). Regeneration in the short-term recall of sentences.
Journal of2~emory and Language, 29, 633-654.
Reitan, R. M. (1992). Trail Making Test: Manual for administration and scoring. Tucson, AZ:
Reitan Neuropsychology Lab.
Rekkas, P. V. (2006). Interference resolution in the elderly: Evidence suggestive of differences
in strategy on measures of prepotent inhibition and dual-task processing.A i.
Neuropsychology, and Cognition, 13(3-4), 341-365.
Reuter-Lorenz, P. A., & Sylvester, C-Y. (2005). The cognitive neuroscience of working
memory and aging. In R. Cabeza, L. Nyberg, & D. Park (Eds.), Cognitive neuroscience of
aging (pp. 186-218). New York: Oxford University Press.
Rey, A. (1941). L examenn chinique en psychologie. Paris: Presses Universitaires de France.
Riby, L. M., Perfect, T. J., & Stollery, B. T. (2004). The effects of age and task domain
on dual task performance: a meta-analysis. European Journal of Cognitive
Psychology, 16(6), 863-891.
Robinson-Whelen, S., & Storandt, M. (1992). Immediate and delayed prose recall
among normal and demented adults. Archives ofNeurology, 49(1, 32-34.
Ronnlund, M., Nyber, L., Backman, L., & Nillson, L. G. (2005). Stability, growth and decline in
adult life span development of declarative memory: Cross-sectional and longitudinal
data from a population-based study. Psychology and Aging. 20, 3-18.
Ruff, R.M. & Allen, C. C. (1996). Ruff2 & 7 Selective Attention Test. Odessa, FL: Psychological
Assessment Resources, Inc.
Salthouse, T. A., Fristoe, N. M., Lineweaver, T. T., & Coon, V. E. (1995). Aging of
attention: Does the ability to divide decline? Memory and Cognition, 23(1), 59
Salthouse, T. A., Rogan, J. D., & Prill, K. A. (1984). Division of attention: Age
differences on a visually presented memory task. Memory & Cognition, 23, 59
Schaie, K. W. (1990). Intellectual development in adulthood. In J. E. Birren & K. W. Schaie
(Eds.), H~andbook of the psychology of aging (3rd ed., pp. 291-309). New York:
Singer, T., Verhaeghen, P., Ghisletta, P., Lindenberger, U., & Baltes, P. B. (2003). The
fate of cognition in very old age: six-year longitudinal findings in the Berlin
Aging Study (BASE). Psychology anddging. 18(2), 318-331.
Somberg, B., & Salthouse, T. A. (1982). Divided attention abilities in young and old
adults. Journal ofExperimental Psychology: H~uman Perception and
Performance, 8, 651-663.
Tulving, E. (1995). Organization of memory: Quo vadis? In M. S. Gazzaniga (Eds.), The
cognitive neuroscience (pp. 839-853). Cambridge, MA: The MIT Press.
Verhaeghen, P., Marcoen, A., & Goosens, L. (1993). Facts and fiction about memory
aging: a quantitative integration of research findings. Journal ofGerontology:
Psychological Sciences, 48(4), Pl57-P71.
Verhaeghen, P., & Salthouse, T. A. (1997). Meta-analysis of age-cognition relations in
adulthood: Estimates of linear and non-linear age effects and structural models.
Psychological Bulletin, 122, 231-249.
Verhaeghen, P., Steitz, D. W., Sliwinski, M. J. & Cerella, J. (2003). Aging and dual-task
performance: A meta-analysis. Psychology and Aging. 18, 443-460.
Wechsler, D. (1997). Weschsler Adult Intelligence Scale-III. San Antonio, TX: The
Wechsler, D. (1997). Wechsler M~emory Scale- Third Edition: Manual. San Antonio, TX: The
Wilson, B., Cockburn, J., & Baddeley, A. (1985). The Rivermead Behavioural memory Test.
Bury St. Edmunds, England: Thames Valley Test Company.
Yesavage, J. A. (1983). Development and validation of a Geriatric Depression Screening Scale:
A preliminary report. Journal of Psychiatric Research, 17, 37-49.
Zacks, R. T., Hasher, L., Li, K. Z. H. (2000). Human memory. In F. I. M. Craik & T. A.
Salthouse (Eds.), H~andbook ofaging and cognition (2nd edition, pp. 293-357). Mahwah,
Shannon Sisco graduated with honors from Calvin College with a bachelor' s degree in
psychology and a minor concentration in biology. She then spent two years working at a
research associate in the Department of Psychiatry and in the Center for Stroke Research in the
Department of Neurology, both at the University of Illinois-Chicago. Ms. Sisco was accepted
into the doctoral program in Clinical and Health Psychology at the University of Florida in 2006.
She is currently there working toward her doctorate in clinical and health psychology, with a
specialization in clinical neuropsychology. She is concurrently working toward her certificate in
Public Health, also at the University of Florida.