THE RELATION BETWEEN
CRITICAL FLICKER FREQUENCY
CARROLL bM COLGAN
A DI'FPFTTIO*N rPCFi F Nr I T. Tv 7 iii. 7:f.t.' A COLt CiiL :-r
T iH E U ,l' i.'P :17, .*- t ,., [..*.
IN PA.PTIA FiLFILEI ENT 'F TH( FUI'-1. IPF iNT; fI.:r H
[,[* PE L ,.J [,,-.**. T.: ,., .i iL.,.,. l ,
L'NIVER5i 1 I I LUP DA.
UNIVERSITY OF FLORIDA
3 1262 08552 2323
ihe author is Indebted to Lr. E. Porter Home, the
Chairman of the .upcrvicory Cor.ittee, for the generous porti-n
of his tLLo and anorgy that uent into the study. heartfelt thanks
ar- also duo ErT. E. L. Kincicley and Z. J. Anderson, representing
the najor, and Drs. G. R. LarLlett and J. V.. Oliver, representing
For help of a special nature, the cutnor wishes to thank
C[ean e.. k,. Little and Dr. ri. E. Iooro of the Univerrity College
iad Dr. J. V. rcquitty, the Univcrsity Exan-inr. Credit is also
dcL Lrs. H. A. t hycr and A. K. K(rtz for aid xid critical advice
on tre statistics.
Thnl:s to, a-lso, to trs. 2. U. Ilemneier, 5. EI.imboriy,
and Ilenry ivundorlich.
TALE OF CNTENiTS
ACiKNOLEDGM NT . . . . .
I. INTRODUCTION . . . .
II. APPARATUS, TEST AND PROCEDURE .
III. RSULTS . . . . .
IV. DI1CUSSION AND CO.CiUSICONS .
1. 5A;Jo aDh STi-JDA.) DEVIATI . . .
2. LiT.aCORR!!L TIOiS. . . ....
PLATE I. Subject and Experimenter at the Apparatus
WIlLIOGRAPHY . . . . .
aIOGRAPHY . . . .
. . 21
. . 12
. . . 20
. . . 25
The present study as desiaiod to investigate the relation
between critical flicker frequency and a nunbor of psychological
variables. These were attention, ameory, perceptual ability, scho-
lastic aipitde and scnolastic achievement.
A Licht flashing on and off may ap;.car to fLic,:er or %ay
appear to luse, depending on a nurejr of en7iron:'ental conditions
and the condition ol tne subject. The frequency of intenrittence at
which some change in the physical stimulation is paralleled by a
change in tne sensation from flicker to "stencay" or from steady to
flic.ier) ic Icoon as the critical flic:er frequency (CFF). Tno
CFF of a civen individual represents his fliccer-fusion threshold
for the conditions under which it uas measured.
According to lateau, as reported in an article by Landis .17),
the first reported investigation relevant to flic.:er -as done by
Ptolon y-Roglonontanus about ,.. D. 150. ?tolmcy noted that if a disc
Ulth sectors of different colors is spun rapidly the colors seam to
fuse anrd become a new and dirffro:Lt color. oince tnat tirLe, the
phenomenon has inturosted many i jvostigators so that much is lkown
about the conditions under which it occurs. ai colorful and detailed
history of CFF, including a survey of the osctblished factual know-
ledge, is given by Landis (17).
The information available on CFF may be divided into three
categories. These are: (a) psychophysical--concerning the relations
betwwn CFF and various stimulus conditions, (b) physiological--
concerning the relations of CFF with various bodily conditions, and
(c) psychological--concerning the relations with the various measur-
able components of mental abilities, characteristics of personality,
Most of the early work on CFF and much of present day research
involves psychophysical investigations. r.ithin areas of agreement
it can be said that CFF is a function of the size, shape, and posi-
tion of the patch of light, that it varies with brightness and dis-
tance of the light. It is influenced by the surrounds of the light
patch as well as the ratio between the length of the light period
and the length of the dark period in each cycle of intermittence.
Complete discussions of these relations and others are included in
the writing of martley ( 2), Landis (17), and Sinonson and Bro ek (31).
The physiological data, while not as numerous as the psycho-
physical, permit wider generalization. Most, if not all, central
nervous system stimulants cause a rise in CFF, i.e., the light is
seen as flickering above the previous fusion-point and a new, higher
fusion-point is established. Most, if not all, central nervous
system depressants result in a lower CFF, i.e., the light previously
seen as flickering now appears steady and there is a new, lower
fusin-point (31). Further, in tho words of Landis:
. any condition or agent which acts to decrease the avail-
able blood msuar and/or oxygen availaolo to the retina or to the
brain decrenses CFF, whereas conditions increasing the efficiency
of the vascular supply increase CFF. In other words, CFF seems
to be a measure of the functional efficiency of tho retina and/or
the visual cartex. ... 17)
ihe psychological data on CFF are not as numerous as the
pszchophyaical and in the light of present knowledge may appear
mnro limited in value compared rith the physiological. The affects
of practice, and t!Leroforc loarnin,, zermi ts be negligiblc provided
that care has been ta-en to insure that the scbjuct is thoroughly
acquainted costcn-ively) with tne phenceaioon .17). CFF va-rics wiut
the dircction:s Civen the s-uject, such that thel- set to see 'fLic:;er"
gives higher value than the ect to see "fusion". studies oy
ic:lcmar 30) and by hroiek, et al. ( 3) show the reliability of CFT
tl be hiCh--on the order of 0.97. Several personality studies have
shown that "introverts" have higher CFF2 than do "extroverts" (31).
Halstead includes a flicker test in a battery of tests designed to
neacure "bitolical intelligence" (il), but he foJnd little relation-
:!up between th'e flic.er test with a lignt-dar, ratio (LD.1) of 1:5,000
and the Ilennon-lelson est: of i' mental Auiiity. manner, on the other
hand, fou..d C. wiUt an a.craie LD2 of 28:1 to vary significantly
witn the hACL (3-). COla3n, iusi 3 LU2 of 1:1, fc nd a a iificant
relatinshi- iuith the Wechslir-bellerae oale, in a :tuuy of acujccts
ranging Li aIg f-rm 67 to 92 years ( 5).
/. oiological theory of lo.i, standJin i3 that mental functions
are intLaateia conrnecced with the functions of the orain. In his
book, Man on his Nat.u:'e (30), ShcrrLnct)n, the physiologist, develops
this idea at great length, citing experimental evidence to demonstrate
the correlation. A similar basic view is held by the psychologist,
Spearman, although in 'ie Abilities of Man (32) he expresses concern
over the inadequacy of present day kPiowledge of physiology for a
satisfactory close fit with established psychological facts. Others
holding to this theory include Kdhler (16) and Lashley (18). As a
matter of fact, the Gestaltists (including Kdhler) assume a relation
of isomorphism (16) between physical events of some degree of complex-
ity in the brain and mental events occurring in the realm of experi-
ence. There is then, a desire on uoth sides to further the integra-
tion of psychological and physiological facts.
It should perhaps be noted that both the physiologists and
the psychologists consider the study of vision important not only
in itself but, by the former, as a means of understanding the central
nervous system and, by the latter, as a means of understanding a vast
array of mental functions and personality characteristics. In
biological symposia held at the University of Chicago, Gelihorn
It is. . not inappropriate to study the functions of sense
organs not as a purpose in itself, D,.t rather as a means of
eliciting fundarmental processes of the central nervous system.
The senso organs including the visual system) represent natural
avenues of approach to the central nervous system. They allow
one to perform experiments on the central nervous system in the
human, under the most physiological conditions. . it ought
to be possible to illustrate fundamental laws determining the
activity of the central nervous system by the study of. the
visual system. (10)
The importance of vision in theoretical psychology c-n be illustrated
by the fact that two present day theories, as presented by Koffka ( i)
and by Hobb ( L), endeavor to explain all of behavior in terms of, or
by analogy to, visual perception. The use of the Rorschaclh sycno-
diagaostic Lest in personality research illustrates this still further.
lo it is that CFF, already considered of wide si -tilicanco by the
physioloist could just as easily oe accepted as of far-reaching
import.Lce, psychologically, if tnh facts warranted it.
It was mentioned anove tnat CFF reflects many major changes in
the brain. This point is made cloar in the following comment of
Si oason and broeck:
In such clearly defined stresses as anoxia or carLon dioxide
inhalation Lboth probably producing Local acidosis) the flicker-
fusion frequency is a sensitivc method for characterizing, in
a quantitative way, the C.S involvement. (:!)
In accordance with oioloical theory, then, CFF should show
definite relationship %rith some psychological function. If it is
as importantly related to the metaialic activity of the brain as
Landis i7) thinks, thon it should be significantly related to an
important relatively oasic psychological ability such ab attention.
Tne present study was designed to investigate sucn a possi-
oillty. In addition to attention, several oUler psychological aoil-
ities were included so that the relationship of CFF to each might
be determined. These were memory, perceptual ability, scholastic
aptitude, and scholastic achievemer:t. because of the imRrensity of
the task of relating CF to all pos-:iule psychological variables,
limitation was necessary and those chosen are of practical importance.
Attention, as a nae for a class of mental phe.ino.mna, has
had a varied career in the history of theoretical psychology.
Spearman, in discussing attention in his c'chio, Do.In the Ages
(33), states: "In truth, there is hardly an element, or aspect, or
relation, of consciousness wherein this 'attention' has not been
located by some one or other." -.cert*ileos, after a thorough review,
he finds that it has a saving grace--"This is that, however diversely
defined, it has nevertheless been uniformly applied." It would
seen that Pillsoury is in agreement, for in his book, Attention.
e may say then, in conclusion of our examination of the various
theories of attention from the side of consciousness, that each
has picked out some more or less important coneonitant process
or some aspect of attention and regarded it as the explanation
of all the remaining parts of aspects. . Attention is not
any one of these things alone, but it is all of them taken to-
gether and more. (25)
Hebb, in proposing a new theory of behavior (13), thought it neces-
sary to face the problem of explaining attention squarely. In his
opinion, the confusion and hesitancy about attention derive from in-
safficient realization of the effect on current theory of admitting
the facts of the phenomenon. He states (13, p. 4):
'he an experimental result maies it necessary to refer to "set"
or "attention", the reference means, precisely, that the activity
that controls the form, speed, strength, or duration of response
is not the immediately preceding excitation of receptor cells
alone. . Almost without exception psychologists have recognized
the existence of the selective central factor that reinforces
now one response, now another. The problem is to carry out to
its logical conclusion an incomplete line of thought that starts
out preoccupied with stimulus or stimulus configuration as the
source and control of action, eventually runs into the facts of
attention and so on, and then simply agrees that attention is an
important fact, without recorgnzing; that this is inconsistent
with one's earlier ascunntions.
Attention then, is the keystone for psychological theories that would
go Dcyond single stinulus-respons.a association.
In line with Hcbb's contention that attention denotes a
"selectivity of response" originating within the individual is the
working definition given by "hilip in 19A8 1',). After aiL extensive
review of the literature on methods of maazurin, attention, Philip
decided that the w.orklin. definition waic.n best fitted the varied
approaches :ras that attention refers to .a -ubject's power
of holding the :niind on a task in spitc of fati.guo and accidenta.l
disturbu-nce.." Using a critorion proposed by hloodrow 1u), he
studied the rcl:tiie ncrit of fourtecn moasroez of attention derived
partly from the literataro and partly from c.ntribations original. ,ith
Ilia. Ho selected five of the sest of' those measursr to onr a battery
suitable for act-itiistratilon to groups.
In severE-l investigations this battery, Knmun as thiiLp's
Test of Attenit~n, has oe@& used with consistent findings. ;aeinku rt
(26) nade use of this battery in her study, "A scale for measuriig Lihe
g-factors in intelligence." aho co;icludes: ". .that underlying
the atLentioni tosts of LroLbuer LhilLip tnuer is a general factor. .."
(2o, p. 7). In 1935 Monachen included ilhilip's Lest in his study (.),
major r factors in cociiti n." lie also found a goneral factor under-
lying the attention tests, Lrt this general factor for attenti:. uwa
intercorrelated with t;ho g;CerJal factors for theo memory and the coni-
tive tests so that he concludes that thero is a "supcr-uneral factor'
underlying all of them. In a work of tre- adous scup the Speam-
Holzinger Unitarl Trait Study (6 ,3h) has reported similar results.
Attention (including the test by Philip, see34, p. 73) is listed
as a "unitary trait" along with eight others (14, p. 1).
Hames (12) has compared GFF with four of the five sub-tests
from Philip's battery, finding two of them, number span and cancel-
lation, related to CFF. Unfortunately, his results are of doubtful
significance because of the distinct possibility for systematic
errors in the UFF determinations. For his source of illumination
he used a General Radio "Strobotac" which gives an extremely short
flash of constant duration. This instrument consequently produces a
flashing light whose light-dark ratio varies with the frequency of
intermittence. In a vast majority of the studies of CFF the time of
the flash has a constant ratio in the flash cycle. Since CFF is in
part determined by the light-dark ratio, Hamnes's results are not
directly comparable to those of other studies and of greater iEportance
is his omthod of measuring CFF. HIames says of his procedure that
the subject was not dark-adapted, but instead his CFF was immediately
obtained. CFF was recorded in one direction only, from fusion-to-
flic;ker. Five readings were taken with the first discarded as practice,
and a mean CFF was computed from the remaining four. The really serious
source of error here is the lack of care taken to insure that each
subject's CFF was valid for him under the testing conditions. This
need for care can hardly be over emphasized. Landis states:
Finally, one must be sure to instruct and demonstrate to
the observer just what a steady liCht looks like at each level
of intensity, and what a fliccering field loo;:s like at each level.
Crosier I 6) hcs described the appearance of a white field flicker-
ii:; slightly below the point of fusion at low-brightness intensity
as smooth, bluish-grey rp'lsation, at lIn-randiun intensity as
spec:od with yellow spots, at medium intuisity as a granular
ruricco, at nedium-hiLih intensity as frostoi, and at that much
that has Lecn cal.le 'practice', as well as much of the variaDility
in results, is dUo to the fA'ct that untrained ooservcrs do not
know urat to look for. (17)
r4emory, more than any other mental. .unction, is the most widely
acccptnd and the most difficult to explain. As bpea-rman L(.3, ,. 161)
notes: 4Alen talking of the act itself, everyone, oven the plain
nan, seems to mern and always to have meant much the same tning."
Explanations however, have centered around t.o radicalLj different
.lnuw: (a) that reonenorinZ so-not'ing from the past is accomplished
by access to tracks stored in the nervous system of the original
perception or tnoaJzht, etc., and (0) tiat tnere is an "'unc.nsciousness"
.bcra p-st exporicnces aro neld, access beilnL dotcrnined ry a caopli-
catol syster. of mental dynamics. both of teset oxplanations date
at least lroea the middle Aces an d both have their modern-day exponents.
"owuovcr oxplain id, tne experinental investigtii3: of0 t:io conditions
inliuoncing nomory stands as one of the Drigntost achiev. nnts of
mnden-r pjacholo y. ho relation cet.eenc CFF and nemory has nat ueen
Although pcrcaption itself has long; ecz- on the psyc.olo.ical
sco:o perceptual abilltj is a raticr recent innovation. It cec.e3
to have oeco.ne ocplicit as a recul of the earlier ..or. of tne factor
analysts, notably J.pearnan, idoinanicr, and Iharsto.'ic (uc). Their
General approach is, periha.s, guest ciar-ctoriLed Dy tie uar.i of
rnurstrin (38). In 1944 Thurstone published A Fact:.rial Stur- of
Perception (37). Included were five of his "primary mental abilities"
which did not correlate with the test of CFF used in this battery.
His test of perceptual ability was not used. There were, however,
numerous approaches to perceptual responses. In general the meas-
ures of perception did not correlate with CFF. Thurstone did not
relate CFF to tests of attention as defined by Philip. It seems
from Taurstone's description of the measurement of CFF in his study
that the CFF determinations were suoject to the sources of error
referred to above in connection with Hammes's study.
Scholastic aptitude is the term used to denote the capacity
to learn academic subject matter. Even though it specifically refers
to academic subject matter, it is clear that that which is measured
oy scholastic attitude tests is, to some extent, measured by such tests
as the techsler-Bellevue and the Stanford-Binet. In practice, however,
the two seem to diverge. scholastic aptitude tests are primarily
verbal in nature (in keeping with their validation criteria) whereas
the major intelligence tests (such as the wechsler-zellevue) give
approximately equal weighting to both the veroal and the performance
test items. This difference in the composition of intelligence tests
and scholastic aptitude tests plus differences in use and therefore
validating criteria have led authors of scholastic aptitude tests to
point out that, at best, their tests give only rough indications as
to the intelligence of testees.
Biological. theory posits a close correspondence between
neurological events ani psychological functions. At the present time
the experimental findings of neurophysioloLy have some correspondence
with psychological findings, uut much remains to be done Lsee ieob,i3).
As new information iaoot toe functioning of the nervous system is pro-
vided by the physiologists, it is i-rortant that this Liortmartin be
studied in relation to psychological Iunictioan ius 1 id vice versa.
Recently CFF has ocen found to Do related to widespread general
activity of the central nervous system. CFF represents the best
sinnie indicator the physiologists now have for estimating the func-
tioninr, efficic-ncy of the central nervous system. The relating of
CFF to psycholo-ical functioning hao now becomnc an important tas:
for psycholojir'. The present study was undertaken as part of that
_reatcr L-s;:. As a result of this study it should Le posaiole, Dy
means of co,.parin. the relations between CFF and the various psycho-
loical variables, to decide whether CFF is a measure of attention
or memory or perceptual ability or scholastic aptitude or, perhaps,
none of those.
APPARATUS, T7STS, AND PROCEDURE
The general procedure was broken into two parts, a group
session and an individual session. Sixty-seven subjects took part
in one of the six group sessions but only fifty took part in the
individual sessions. Seventeen not taking part in individual sessions
failed repeatedly to keep their appointment. From the fifty there
was a final reduction to forty due to the following: two had scores
that were considered invalid because of difficulty with the English
language on tests, two -omen were dropped in view of difficulty of
scheduling, one subject was hospitalized, one subject never saw fusion,
several subjects failed to keep further necessary appointments. The
forty subjects who satisfactorily met all the requirements of the
study were male college sophomores with three semesters of college
work completed. They were all in good standing and in good health.
The tests suitable for administration to groups (attention, percep-
tual aoility) were given at the group session, while the tests limited
to individual administration (sensory attention, memory, CFF) uere
given at the individual session. Scores on scholastic aptitude and
scholastic achievement were obtained from university officials. At
the individual session each subject's height was recorded so that a
gross physical measurement might be included in the intercorrelations.
The light source used for the CPF measurements was the glow
modulator tubo, Sylvania R-1130-;, modulated by an electronic snitch.
The wave-torn was essentially rectangular, thus linitino the latency
and decay of the liflt source to the time required for ionization
and de-ionization of the gas contained therein .nhich was approximately
This tube was part of a circuit unicn allows variation of the
Brightness of the light source. The circuit was stable and noise-
less in operation. it had been used in several previous studies,
see Colgan (Li ) and Saucer (2U,29). Suitable regulating devices
were included to filter out fluctuations in the 110 volt, 60 cycle
The circuit consisted essentially of a positive bias multi-
vibrator with symmetrical time constants. Large frequency increments
were controlled by a switch which places the correct value of C in
the grid circuit of eacn tube of the multiviurator. Small frequency
chances of the order of 3:1 were made oy the adjustment of the posi-
tive Dias potentiometor.
The signal output of the multivilrator was developed across
a 5,000 ohm resistor. A 6587, functioning as a wide-band grounded
amplifier, is connected across the same resistor, so that the 65H7
signal input was transmitted via the cathode in accordance with con-
ventional practice in grounded grid circuits ,hi). ahis eliminates
phase shift and other forms of wave distortion associated with RC
coupling networks. In addition, these tabes served as clippers and
wave shaping circuits, so that the gatin, signal applied to the Eon-
trol tube had an extremely short rise time.
A 6V6 was used to control tle current throoii the R-l130-i.
In order to control this tube it was connected as a direct-coupled
amplifier across the plate load resistor of the 6j7il, so that when
the 6Si7 was conducting the 6V6 was cut off by apiro:icnately 125
volts negative bias. ..hen the 6&H7 was not conducting, the bias
on the 6V6 was the value imposed by a 100 ohm cathode ra~istor.
Further intensity control was secured by the use of a voit-ge divider
in the plate circuit of thc 6V6.
The sat.uiu3-patch was a 10-sided polygon, white in color,
4 mm. across, and 1000 mm. from the suoj-cts', pyes. hcn flas&irg,
the stimulus-patch had a orignl.ross of 23.71 ioot-lanDerts and a Li,;ht-
dark ratio of 1:1. Light and test-patcn were enclosed in a large
rectangular box, the insides of which ioer flat-blac... he szoject
observed the test-patch by means of a vicerinv hood attached to one
end of the box (see Plate I).
In general the procedure for the measurement of CFF was the
sauce for all subjects. Each spent approximately 50 minutes prior
to the testing in a room illulinatcd by relatively low-level arti-
ficial illumination. For the measurement itself, the .cauject fixated
the patch binocularly. Flicker and the fusion-point were given
ostensive definition for the subject. Following several preliminary
trials, five ascending and five descending trials were given the
subject who was instructed to report when the flicker disappeared
and reappeared. The average of these ten determinations was taken
as his mean CFF. The rate of change of the flash rate was rapid
and irregular. The initial rates of repetiioL were rand-irizod
and the exposure was continuous for each trial, varyin-i irom 2 to
6 seconds. The light was off between trials. The exierinreintal
room was darkened throughout all determinations.
The preliminary trials served to increase the reliability of
the CFF determinations. Investigation had shown that experienced
subjects gave initial judgments with little or no scatter, whereas
among naive subjects, some gave highly consistent initial judgments
and others gave widely scattered judgments initially, but after four
or five detenninations they became consistent also. This variability
or practice effect was controlled by taicing as many ascending and
descending determinations (fron 2 to 10) as was necessary to insure
that each subject was civbi; consistent judgments. For 19 subjects
excessive variability necessitated a retest. The preliminary results
were not used in the determination of CFF for any subject.
The test selected as a measure of attention was tPilip's
Test of Attention. As mentioned in Chapter 1, this test has been
found to be a suitable test of attention. It is coaoosed of five
subtests and requires slightly over an hour to administer. Special
ansujer sheets are available and the test is suitable for administration
to groups. Complete instructions as well as scoring keys and procedure
are given by rhilip (2t). Several of the subtests are timed. The
use of a blackboard or similar device seemed nocossary to make sure
thnt -al of the subjects understood the instructions for sone of the
The five subtests were named by Philip as: (a) Number span,
(b) Iultiplication, (c) Alphaoct, (d) Addition, Laid (e) Cancellation.
The Nu.ioer ispan test. consisted of twenty-four numbers, from one to
nine digits, with two to three letters randomly placed ameao them.
These were continuations of letters and digits dictated uy the ex-
aminer writh the subjects required, at a signal froa the eyamniner,
to rite only the digits in their proper order and to disregard the
letter. rho Ahiltiplication test requires mental multiplication of
relatively lonj numbers, itkewioe dictated by the examiner, and the
retention of tne answer in the mcanry until the si3ial is given to
Twrlte down only the answers Ln their proper place. Dhe Alphabet
test was original with ?hilip and consists of the olloUiing: A
letter of the Japhaoet is dictate, follow cu from one to five
digits. The s-oject, at a given &ignal, is re.uirea ta writo cJwn
tre letters of tne alphabet, in the sequence in which the aiitG were
givo:i, counting from the initial letter. Thus if' F-35 is dictated,
only I N R is to be written down. The uore: must De done mentally.
The Addition test consists of numbers of from one to six digits pre-
sented on the answer sheets writh the subject required to adJ them
horizontally in his hnad. The numuors on any one line varied in
length so that care is needed to plane heo uiits, tons, hundreds,
otc., in their proper column. Tie Cancellation test represents a
modification by Phiip of a test by 6tcrziLuer. It consists of
seventeen lines of randomly assorted letters of the il-,habet in groups
of from one to four letters. The groups are also randomly arranged.
In a ten minute time period the subject is required to cancel letters
according to their position and the &ailic.ioiLtit of one or more of
three rules given for this purpose.
In his study Philip called his test a test of "abstract"
attention and used a modification of a test by Nfnsterberg for the
measurement of "sensory" attention. It was thought desirable to
include this test in the present study to investigate the possibility
that CFF represents more a measure of "sensory" rather than abstract"
attention. Describing his test of sensory attention, Philip stated:
A pack of thirty-two cards had marked on each the four colors
black, red, green and purple in thirty-six randomly distributed
dots, according to the following scheme: Two cards had sixteen
olaci dots and of the remaing colors the following numbers,
seven, seven, six. Two cards had fourteen blacks, and seven,
seven, and eight respectively of the others. Two cards had twelve
slacks, and eight for each of the others. Two cards had eleven
blacks, and eight, eight and nine for the others. This scheme
was followed for each of the four colors. (24, p. 37)
The subject is required to sort these cards into four piles, accord-
ing to the predominant color. Three trials are given, with means
for time and for errors recorded.
As a measure of perceptual ability, the (Serics it) Likert
and Quasha revision of the Minnosota Paper Form board Test was used.
This test has been widely used and publicized (19, 7 ). It is suitable
for group testing.
As a test for memory, the standardized Memory Scale of *,echsler
(39) was adopted. This test was designed primarily for clinical use
and consists of seven subtcsts: (a) Porsonal and Current Infonrmtion,
(b) Orientation, (c) Mental Control, (d) L)gical M iory, (e) memory
Span, (f) Visual Reproduction, ([) Associate Learning. The first
three were included, Wechsler states (39, p. 87), because of their
value for clinical diaGnosis--even though thny discriminate "...
very little or not at all Detween normal or even near-normal subjects."
.inco the subjects in the present study wore at lost in the Latter
cateeor7 tho first three subtests were not used. Appropriate points
wore allowed all subjects on these tests, however, so that tt.-al
: eichted scores could be attained for comparison with Wechsler's norms.
The other subtests .e*re scored according to the toat manual.
Scholastic aptitude was measured oy meruis of the American
Caoncil on -ducation Psychological Exainination (ACE), 19L9 edition.
This test had been taken Dy all subjects when they first entered the
university as freshman. The scores were outalnod from the University
Sxa2iiner's oilice. Three scores are derived front this test: ka) a
,uantitative or 4 score, (b) a Linguistic or L Scoro, and (c) a Total
or r score. All three have extensive norms for comprrison purposes.
Scholastic achievement was determined uy computing the honor
point average (HPA) for each subject on the basis of course grades
since entering college. A grade of "A" receives four honor point,
a crade of ".;" three points, a grade of "C" two points, a grade of
."" ono point, and a grade of "S" no point. Access to these grades
was furnished by the Lean of the Ualversity Colloge.
As a means of reporting the relationships between variables,
Pearson product-moment correlations were used. The variables fell
into three classes: (a) experimental variables, (b) test variables,
and (c) subject variables.
The average of ten determinations of a subject's fusion-
point was taken as his mean FF--rocorded in cycles per second (cps).
A subject's score on the sensory attention test was obtained by add-
ing the average errors to the average time in accordance with a
formula used oy thilip I2h).
The Minnesota Paper Form board (P. Fm. Ld. ) and the ACE were
scored according to their respective test manuals, scores weighted
for age were obtained from the memory test, while the perceptual test
scores were raw scores. The attention scores for the Philip's battery
of subtests were weighted according to a formula given by Philip (24).
Each subject's height was recorded to the nearest centimeter.
His HPA was taken as the average number of honor points per semester
hour credit. The course work covered general introductory freshman
and sophomore subjects.
In Taole 1, measures of central tendency and variation and
also a measure of variability of the central tendency are presented.
As representations of these statistics, the following were obtained
in order: mea; (M), standard deviation (3), and the standard error
of the noan (rw).
DS- .TIOiiOa, ,.l;u Si'~;..i, Oi.0u OF D-6 KrA.-
(1- = 40)
Measure I o oM j eauure 1 o aa
CFF (cps) 36.9 1.8 0.3 HPA 2.5 0.8 0.1
Attention 89.6 12.4 1.9 Sensory 155.0 35.0 5.5
.Jo. span I1S.h 5.8 0.9 AC1. (total) 115.7 17.0 2.7
.tult. 6.5 1.6 0.3 .uant. 4h.0 8.2 1.3
Alphaoct 11.8 L.O 0.6 Linguistic 71.7 12.1 1.9
AdnitLion 13.9 h.7 0.7 ilcmory 103.2 4.9 0.6
Cancel. B.2 2.6 O.h A. Ld. 17.h 7.3 1.2
Hcidit (km) 179.9 6.1 1.0
To deter.ice the relation DetweLn CFF and each of the other
variaoies, correlation coefricients were com.juted. Ihis tecclique
of statistical analysis was iaso usoe to determine the ma6nituce and
direction of tihe interrelations among the scores on the tests ol
attention, perceptual aoility, memory, scholastic aptitude, ual
scholastic achievement. The measurcments of height cwre correlated
with scores on all of the auovn tests.
Correlation coefficients are presented in Taole 2. These
coefficients permit evaluative inferences about GFF--both aoout
its psychological and its physiological explanations. In addition,
they permit interpretations aoout the relations of attention, as
it is measured by Philip's test, with the other psychological aoil-
ities. Relations between attention and other psychological abilities
have frequently been hypothesized or discussed out seldom studied
In interpreting these coefficients of correlation it should
be noted that for an N of 10 a correlation coefficient (r) of approxi-
mately 0.30 is considered significantly different from zero at the
5 per cent level of confidence*. Similarly an r of approximately
0.40 is considered significant at the 1 per cent level of confidence.
Because a high score on the sensory attention test means a
poor performance and a low score signifies a good performance, a
negative correlation with any other test should have a positive sign
to be readily interpreted. Therefore the signs of the correlation
coefficients between this test and each of the others have ueen
*'he standard error of r for various values of r is as follows:
for an r of 0 to .20, .16; r of .21 to .30, .15; r of .31 to .39,
+ .lh; r of .o0 to .45, .13; r of .46 to .52, 1 .12; r of .53 to .58,
S.11; r of .59 to .63, 1 .10; r of .6h to .68, 1 .09; of .69 to .72,
.08; r of .73 to .76, + .07; r of .77 to .80, .06; r of .81 to .84,
S.05; r of .85 to .87, 1 .Oh; r of .89 to .91, 1 .03.
TfbL-J OF IilLRCOQO;dAiAiOi
-easure 1 2 3 4 5 6
sensor r Atte-tiona
I-inn. P. Fa. Ad.
. . +0.23 -0.27
+0.23 . +0.67
-0.27 +0.67c . .
+0.12 -3.51c +0.10
S0.32 +0.703 +0.31'l
40.07 +0.76c <0.29
+0.16 V3.23 -0.26
-0.15 +0.37) -0.28
40.02 40.550e 0.16
+..05 0.50c +O.J7
-0.02 +0.60c +0.17
+O.ObL 0.3)0 +0.07
-0.01 +0.23 +0.01
+0.12 +3.LOC +0.18
-0.0h -0.03 -0.11
aThe correlation coefficients are rcrersed in sion--see
jaicnificant t t o 5 level of caLlidea.Le.
c.lgnificanL t t he 1% Level of confidence.
7 8a 9 10 11 12 13 1l 15
40.16 -0.15 +0.02 +0.05 -0.02 +0.04 -0.01 +0.12 -0.Oh
+0.23 +0.37b +0.550 +0.54c 0.60c +0.39b +0.23 +0.)00 -0.03
-0.28 -0.28 +0.16 +0.07 +0.17 +0.07 +0.01 +0.18 -0.11
+0.12 +0.36b 0.33b +O.lIOc +0.20 +0.19 +0.00 +0.10 +0.13
+0.27 +0.10 +0.27 +0.29 +0.18 +0.11 +0.14 +0.25 -0.05
+0.25 +0.310 +0.62 +0.60 0. +0.6 +0.l3c +0.25 +0.h2C -0.O0l
. +0.06 0.32 +0.38b +0.19 +0.32b +0.04 +0.03 +0.15
+0.06 ... +0.h6 +0.36 +3.0c +o0.38b +0.15 +0.14 -0.05
0.32 0.6 0.76 0.+0.320 6C + 76 9C 0.32b +0.45c -0.17
+0.38b +0.360 +0.76c 4038b +0.4l1 +0.29 +0.38b +0.10
+0.19 +0.0Oc +0.89 +0.38b .. +0.27 +0.24 +0.38b -0.30b
+0.32b 10.38b 0.39b +0.41c +0.27 . +0.8c -0.05 -0.20
0+.04 +0.15 +032b +0.29 +0.24 +0.8c0 . -0.27 -0.26
+0.03 +0.1L +C.45c ,0.38b +0.380 -0.05 -0.27 . +0.16
+0.15 -0.05 -0.17 +0.10 0.30b -0.20 -0.26 +0.16 . .
uISCUSLIA. Allb C jiiCLUJIIO.a
Discussion of the results of this study is presented in three
parts. First, the particular method of analysis appropriate to the
study is discussed. Then follows a general discussion of the group
results on each test or measure considered separately. The last
section deals irith the presentation and interpretation of the inter-
relations among the variables, including the conclusions to be drawn
from the study.
A method of analysis suitaulo for the present study is derived
front one referred to by J. S. Mill a: the joint method of agreement
and difieronce (3, p. 220). Lnployinc this metnod in a now applica-
tion, Spearman (J., p. UI) demonstrated its usefulness as a criterion
for ovaluatin interrelations expresuso in corrolational form. To
meet tno agreement criteria, CFF should correlate Aignificantly with
not only one variaDle--such as sensory attention--but also with each
of the other variables included in the study that can Oe adequately
described as measures of a closely related function--in this erxaplie,
the attention battery of lhilip. Following the ex-aple, in order for
the difference criterion to Do satisfied, CFF should correlate little
or not at ill i.ith each of the variables that can be nde.;uately
described as not measuirin attention or any closely related function.
CFF should meet both criteria to satisfy the method of agreement
Before considering the interrelations among the variables,
the group results on each of three separately should be noted. The
average OFF was 36.9 cps, with a standard deviation of 1.8 cps. 'his
average value is about the same as that found by several investigators
S31). The standard deviation found here, althouEh it is less than
that reported by Simonson and brolek (31) for a sample of 32 men,
is sufficient in view of the high reliability associated with CFF,
especially when the latter is carefully determined, to siow whether
a relation exists between CFF and any of the variables included in
the present study.
Means and standard deviations for Philip's Test of Attention
are comparable to those Philip obtained for the 18 and 19 year old
boys and girls in his study (24). This is trae whether the comparison
is between total scores or between scores on any one of the subtests.
For the sensory attention test, Philip reported a mean and standard
deviation for 49 college males which are similar to those found in
Comparisons are also possible for each of the other variaoles.
The mean value found for the 'irinne:za taper Form board, 47.4, is
approximately the sane as that given in the test manual for the 50th
percentile, third year engineering students or for the 85th percentile
for liberal arts freshmen. Mean and standard deviation for the memory
test are similar to the values reported by Wechsler for subjects of
comparable ase. iccordi ng to the norms for the AC., the ncans found
in Table I for Total, j. and L, have percentile ranks of 62, 65, and
6L, respectively. The average IRA is higher than the average for
University of Florida males and the average height of the group is
greater than that of the average American male.
Against tiis background, the interrelations aaong the v:ri-
ables may be discussed. CIF correlated with the attention test of
Philip *0.23 and with the teat of sensory attcution -0.15. r1either
of these coefficients is siuiilicantly dilfforent from zero. One of
the subtests of rhiLip's test, Alphabet, correlated with CFF tb the
extent of +0.32. On the basis of chance fluctuations, an r of this
magnitude could be expected to occur approximately five times out of
100 if the true r were zero.
Applying the criteria of agreement and difference to these
interrelations, it is concluded that for subjects and testing, con-
ditions similar to those that here used in the present study CFF is
not relatoi to attention as measured by either rPilip's test or the
test of sensory attention. These test-, as measures of attention,
dopond on the subjects concentrating on the t,-t natter to a maximum
extent and cherefore reflect individual differences in this maxianm.
There are other ways of describing the variation of attention. It is
possible for attention to vary from time to time within the sane
individual. The lack of a suitable measure of this aspect of atten-
tion prevented its inclusion in the present study.
OFF correlated nearly zero with the *j, L, &id T scores of
the A.-. Interpreting the CE as a measure of intelligence, Tanner
(36) reported significant correlations between CFF and the ACE.
Colgan ( 5) found similar results with the beehsler-Bellevue Intelli-
gence Scale. Since both Tainer and Colgan used testing conditions
for the CFF determinations siLilar to those used in the present study,
the apparent conflict in results deserves discussion.
To begin with, Tanner measured the shortest noticeable dark
period for several fixed light periods. This means that for a given
fixed light period, the dark period of each cycle was reduced in length
until the subject reported the absence of flicker and then the dark
period was increased in length until the subject reported fliceter.
The length of the dark period at the point of transition tas determined
by one ascending and one descending determination) was taxen as the
shortest noticeable dark period. Thus the light-dark ratio (LDR)
was variable. In the present study the LDR was constant at 1:1,
i.e., the light and dark periods in each cycle were equal and were
shortened (or lengthened) by the same amounts whenever the frequency
At the fixed light period of 16 milliseconds, Tanner's 25
subjects gave an average LDR of approximately 1:1. Since this is the
constant LDR used in the present study it is interesting to note that
Tanner did not obtain significant correlations with the ACE at this
setting (35). There is, then, no conflict with the present findings
but rather corroboration. His positive findings with the 38 and the
8h nillisecond light periods stand in need of corroboration also;
tlero are reasons for believiLi that the CFF of a given sauject is
different when measured with a constant LULR from that obtained when
usLng a variable LDR. Coasentiji: on this, Landis i;) states that
u.iore the LD1 varies with freuency ". .tne contour found by Lraph-
Lng frequency against intensity has a different position from that
were the time of the flash has a constant ratio in flash cycle."
The app-artus used in the Moosehaven study 5) is the sane
as that used in the present study, with a LDR constant at 1:1. The
subjects studied ranged in age from 67 to 92 years and they were
trstedJ with the ihecaler-Bellpvue Intplli.inco Scale (Ui-). by
neoois of partial correlation, Colgan demonstrated tLat for his L,0
subjects CFF was related to the v-b and not to aoe except in so far
as the latter was possibly .un underlying datorminant of both tne W-b
ccores and the CFFs. lhe high correlation oetw:een CFF and esca of
the performance sutoests accouita, for the most part, for the bish
correlation betwoun CFF and the total score on the W-L.
In the present study, CFF was found to De unrelated to the
/.C. Studies ny Sartain (-,) and oy n/derson, et al. k i) have sh:un
the h-B performance IQ to have little or no relation with the ACE for
college students. It is not surprising that CFF, which correlates
highly i.ith the 'W-3 perfor= noc scale, does not correlate sicnifi-
cantly with the I.C.
In view of the above, it is not unexpected that CFF should
not correlato siiiAif1catly l.ith ViA. Tho purpose or function of
the AC; is to predict ILr,--at least to sorle extent. In. the present
study, ACE is definitely related to HPA and just as definitely not
related to CFF. In addition, the W-1 performance scale was found
by Anderson and by Sartain to be only slightly related to HPA.
The bochsler Memory Scale correlated to an insignificant
degree with CFF. Wechsler found a relation of sufficient magnitude
between raw scores on his memory scale and age to warrant weighting
these scores in terms of the W-B full scale, but points out (39, p. 90)
there is no relation between the memory scores and the W-B without
variation in age of appreciable scope.
The relation of CFF to the W-B Performance Scale deserves
special attention. Colgan found a correlation of 40.48 between scores
on these two variables, using elderly men as subjects. A coefficient
of this size, for an N of h0, is significant from both a statistical
and a practical standpoint. It is possible, however, for the W-B
Performance Scale to be related approximately to the same extent
with some third variable totally unrelated to CFF and vice versa.
Nevertheless, it is significant the way the relation between CFF and
the performance scale is paralleled by their relations with several
other variables. In Colgan's study both CFF and the performance
scale iere significantly related with age. In Anderson's and Bartain's
studies, using college students as subjects, the performance scale was
found to have very little relation to either the AGE or the HPA. In
the present study, again with college students as subjects, CFF was
found to have little or no relation with the ACE or the IPA. echisler
found the performance scale to have little relation with scores on his
emoary test for subjects of about the same age. In the present study
the subjects were all approximately the same ago and CFF was found to
have little or no relation to their scores on Wachsler's memory test.
nLds is either a remarkable set of coincidences or further evidence
of definite relationship between CFF and tre W-b perfonqcnce scale.
RFrther research along tnis line is indicated. This nuch can be stated
at present: none of the findi-as in the present study ii any way
contradict the observation made Dy Colgai that CFF and thLc; -5 per-
formance scale are related.
CFF did not correlate significantly with the Minnesota Paper
Fonr board or with the height of the suojecta. It is concluded
that CFF is unrelated to perceptual ability or to height. The
specific aspect of perceptual ability measured by the Minnesota Paper
For, board was found by tMurphy (22), in a fcctorial study, to oe tne
ability to manipulate spatial relations. The lack of relation between
CFF and height. does not preclude possible relations with other body
sises or proportions not studied.
To sumarize the findings of the present study, CFF was found
to be unrel:-toa to attention--oither abstract or sensory. Neither
was CFF related to scholastic aptitude or scholastic achievement. In
addition, there was little or no relation ooservaolo uetween CFF and
perceptual ability, memory, or height. In regard to some of these
variaules CFF exhiDitod a lac, of relation sirdilar in pattern to that
reported by other investigators for the r-b performance scale.
Iriarnuch as attention has seldom been studied in relation to
other psychological abilities as measured by modern standardized
tests, the results of the present study that bear on this point are
of great interest and practical importance. both Philip's Test of
Attention and the measure of sensory attention correlated very signi-
ficantly with the ACE (+0.55 and +0.46, respectively). Philip's test
correlated with HPA (+0.40) almost to the same extent as did the
ACE (40.45). By means of multiple correlation, HPA was correlated with
ACE and the attention battery of Philip. The multiple correlation
coefficient was +0.54. To provide a means of evaluating the influence
of attention on the relation beoteen the ACE and HPA, a partial corre-
lation was conmuted between ACE and IIPA with attention statistically
held constant. The resulting coefficient ias +0.30. The relation of
attention to HMA with the ACE held constant is represented by a coef-
ficient of +0.20. The test of sensory attention, Philip's Test of
Attention, and the ACE all correlated with perceptual ability to about
the same degree (+0.38, +0.39, and +0.39, respectively). Neither the
attention test nor the sensory attention test correlated significantly
with either memory or height.
On the basis of the intercorrelations between then, the test
of scholastic aptitude seems to be measuring to a considerable extent
the same function as does the test of attention. If Philip's test
is measuring attention in the sense defined by him, this finding is
entirely reasonable. Any careful observation of the ability require-
ments for acadunic success will show attention to be one of the traits
differentiating good from poor students. FPrther, the correlation
found between the test of attention and IIFA substantiates this obser-
vation. That attention is not the only ability needed for scnolastic
aciievo,.ient is demonstrated by the significant r Oot.oan ACL and ILPA
with attention statistically held constant. The r between attention
and H.iA, o0. thu other htr.1, loses significnce iuhna the ;.C is held
coA.stuit. Anlothor ability, besides attention, noasurod by the ,.C
is nemory. This is demonstrated by the ftnding that menoxry correlated
sELtiiLfcantly ulth the AGE uut not ith either of the attention tests.
The ACE exhiDited an interesting pattern of intercorrelations.
Lesidos correlating highly with its own parts, the ACi correlated
to a si[i[ticant degTee uith almost all of the other variables.
Lcholastic aptitude was trhus related to memory, prceptual ability,
abstract LnJ sensory attention, and scholastic achLevement. Cnly
CrT, height, r-nd two of tre attr iti .n subt.sts (!iumer Span and
Alphabet) did not corrolato a-igiific:uLt1y id u the L.C. Lyon so
hei;ht wan related to the LinLuistic part, with tho r barely reach-
Ln. the 5Z lovol of confidenco--a finiiin co.,siderea of no L.portance.
To return to a discussion of CFF, it is apparent that this
". msinsitive indicator of neurological efficiency" (!Landis, 7)
is no lssitive indicator of any of the joveral psycholo.icaCl functions
included in the pruueat study. At is of course posaiule that CFF
is sucij an indicator for soao psychological uniction nat ctudled
here, bit tictler this is so or not furtihr specificatio. of the
physiological nature of CFF seems desirable. There i. the questionn
of whether a high CFF for one individual neans that his nurrous system
is more "cfL 'jricnt" than that of an individual with a low CFF. Or
perhaps a high CFF is "normal" for one person, while a low CFF is
proper for another--with CFF being a "sensitive indicator" for varia-
tions (intraindividual) from this norm. either specification of the
physiological nature of CFF is more desirable than the present
For suojects and testing conditions similar to those used
in this study, the following conclusions are presented:
1. CFF is correlated with attention, as defined oy Philip,
to the extent of a Pearson r of +0.23. This r falls within
fiducial limits (1%) +0.58 and -0.19. CFF is correlated
with sensory attention to the extent of an r of -0.15.
This r falls within fiducial limits (1%) -0.52 and +0.27.
Ho definite relationship was found in this study between
CFF and attention.
2. The results of this study indicate that it is probable
that the correlation between CFF and scholastic aptitude
as measured by the psychological Examination of the ACE
is low. The r of +0.02 with its corresponding fiducial
limits of +0.42 and -0.38 indicates the extent. The
absence of relation found between CFF and the ACG. in no
way contradicts the relationship previously found by the
writer between CFF and the Wechsler-bellevue Intelligence
3. Teio Penrson r toetoeen ho.or poi-t a--orace -and CFT wac
40.12 ..ith fiducial limits of .0.50 and -0.29. .colastlc
ac;ievo-aent as representca btr h3.ior point average and CFF
are probably not relatea to any appreciaole ext.nt.
I. here is prooaoly little or no relation Jot:.,an CFF and
perceptual aluiity as measured by the ilinnesota Paper Fona
board nor between C."F and memory as moas-red by the :.echsler
1 Coory Scale. The fiducial limits for the r Detween CFF and
the Miinnesota L'rer Forni board (JO.0) are +0.143 nd -0.36.
The corresponding values for the r betccwnO CFF and th 4 ech-
alor 'Memory Scale L-O.0l) are *4O.1 and -0.39.
5. 'l:iiCt anjd CFF are probably unrelated for a..ult szDjccts.
T-o exb-nt is iidicate.l uy an r of -0.04 i th its fiducial
linits of -3.13 aid +0.36.
6. L'hilip's Te't of Atterntioli is sLTii'iccALtiy related to the
hAC'. Die r of ).55 with its fiducial Lirts or ).70T ao:a
r0.19 indicates the extent. acniolastic aptitcde iz a lunc-
tioL of attention, memory, perceptual ability, and possibly
ot:er metal aDitities not represented in the present ztudy.
7. The measure of scholastic aptitude, the AC:, was foand to
relt., to the measure of scholastic achiev.eent, H.r, to
about the sano extent as t.nat reported in tU lioratu.re.
8. '3oro is need for further clarification by phycio ogists
of the sopcific status of CFF in neurop.nysioloiceal theory.
Further study of the relation of CFF to other psychological
variables is indicated since many experiments have shown
C.F to be importantly related to events occurring in the
central nervous system.
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Carroll Monroe Colgan was born May 12, 1925 in Jacksonville,
Florida. He attended elementary school in Jacksonville and Marianna,
Florida, and graduated fror Andrew Jackson High School--receiving
his diploma in absentia. Upon his discharge from the Army Air Forces
he entered Jacksonville Junior College and received a diploma in
May, 1947. He then enrolled at the University of Florida and graduated
with honors and a Bachelor of Science degree in June, 19h9. Entering
graduate work in Psyc'oloi also at the University of Florida he
received the degree Master of Arts in June, 1951. He was employed
during the same period as a graduate assistant in the Psychology
Departnont. Upon receipt of a Fellowship from the United States
Public Health Service he continued his studies in 'syc-ology with
Philosophy as a minor while engaged in several research investigations
at the Moosehaven Research Laooratory in Orange Park, Florida.
The author is married and has one son. He is a member of
Phi ueta Kappa, ihi Kappa Phi and an associate member in the Society
of the Sigma Xi and the American Vsychological Association.
This dissertation was prepared under the direction of the
chairman of the candidate's supervisory committee and h?.s been
approved Dy all members of the coaiittee. It v;as submitted to
the LDan of the College of Art r.nd Sciences and to the Graduato
Council and was approved as partial fulfil-ment of the rduiroments
for the dgreeo of Doctor of Philoaophy.
August 9, 195h
Dean, CotiLet of Arts ana sciencess
Dean, Graduate school
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