INTELLIGENCE 7, 227-252(1983) Fluid and Crystallized Intelligence and Primacy/Recency Components of Short- Term Memory* JOHN CRAWFORD Universi~ of New South Wales LAZAR STANKOV Universi~ of Sydney Primacy and recencyrecall measures, obtainedfrom both free and probed-recall tasks, were includedin a battery of tests which also containedmarkers for fluid intelligence, crystallized intelligence,and cognitivespeed factors. Our results confirmedprevious findings that for subjects within the normal range of abilities, recency recall from probed-recalltasks is more closely linkedto intelligence than is primacyrecall. A new finding was also obtained: that primacy recall is correlated more with measures of cognitive speed than is recency recall. These results are discussed in terms of the concept of working memory and its relation to intelligence. Several experiments attempting to investigate the mechanisms underlying cor- relations between short-term memory (STM) and intelligence have adopted, at least in part, concepts contained in multi-store models of memory, such as proposed by Atkinson and Shiffrin (1968). A major success of such models was the accounting for serial position data from experiments involving free recall of supraspan lists. Of particular interest, recall of terminal and nonterminal items, in an immediate recall task, are interpreted as measuring different processes. Terminal items are retrieved from one or more short-term memory stores or buffers, sometimes referred to as the Primary Memory system (e.g., Waugh & Norman, 1965), while the recall of earlier items depends on their transfer to a relatively long-term Secondary Memory system. This transfer was thought to be influenced by such 'higher order' mental processes as choice of efficient rehears- al strategies and the use of complex semantic relationships between memory items. It was thus postulated that primacy recall (i.e., recall of the last few items), which was regarded as reflecting more basic mental functioning or "shal- lower levels of processing" (Eysenck, 1977). Such expectations were initially confirmed but largely from studies comparing *This paper is based upon an Honors thesis submittedby the first author and supervisedby the second author. Correspondenceand requests for reprints should be sent to John Crawford. School of Psychology, Universityof New South Wales, Kensington,N.S.W., Australia 2033. 227
Transcript
INTELLIGENCE 7, 227-252 (1983)
Fluid and Crystallized Intelligence and Primacy/Recency Components of Short-
Term Memory* JOHN CRAWFORD
Universi~ of New South Wales
LAZAR STANKOV
Universi~ of Sydney
Primacy and recency recall measures, obtained from both free and probed-recall tasks, were included in a battery of tests which also contained markers for fluid intelligence, crystallized intelligence, and cognitive speed factors. Our results confirmed previous findings that for subjects within the normal range of abilities, recency recall from probed-recall tasks is more closely linked to intelligence than is primacy recall. A new finding was also obtained: that primacy recall is correlated more with measures of cognitive speed than is recency recall. These results are discussed in terms of the concept of working memory and its relation to intelligence.
Several experiments attempting to investigate the mechanisms underlying cor- relations between short-term memory (STM) and intelligence have adopted, at least in part, concepts contained in multi-store models of memory, such as proposed by Atkinson and Shiffrin (1968). A major success of such models was
the accounting for serial position data from experiments involving free recall of supraspan lists. Of particular interest, recall of terminal and nonterminal items, in an immediate recall task, are interpreted as measuring different processes. Terminal items are retrieved from one or more short-term memory stores or buffers, sometimes referred to as the Primary Memory system (e.g., Waugh &
Norman, 1965), while the recall of earlier items depends on their transfer to a relatively long-term Secondary Memory system. This transfer was thought to be influenced by such 'higher order' mental processes as choice of efficient rehears- al strategies and the use of complex semantic relationships between memory items. It was thus postulated that primacy recall (i.e., recall of the last few items), which was regarded as reflecting more basic mental functioning or "shal- lower levels of processing" (Eysenck, 1977).
Such expectations were initially confirmed but largely from studies comparing
*This paper is based upon an Honors thesis submitted by the first author and supervised by the second author. Correspondence and requests for reprints should be sent to John Crawford. School of Psychology, University of New South Wales, Kensington, N.S.W., Australia 2033.
227
228 CRAWFORD AND STANKOV
performances of normals and retardates. Ellis (1970) explained such data by proposing that individual differences in rehearsal proficiency produced the lower Memory Span scores in retardates as compared to normals. More recent data, however, suggests that for subjects within the normal range of abilities, in fact, the reverse is true. Cohen and Sandberg (1977) found that for probed serial recall of digits, recency measures were more closely related to intelligence than were primacy measures. Moreover, they presented evidence that this effect could not be explained in terms of individual differences in rehearsal patterns, encoding efficiency, or susceptibility to proactive interference. They concluded that indi- vidual differences in the "persistence" of traces in the short-term store underlie the link between Memory Span and intelligence. In a more recent paper, Cohen and Sandberg (1980) proposed an alternative explanation, that it is the "encod- ing of items-in-order" under memory load which is the critical mechanism producing correlations between IQ and recency recall.
Horn, Donaldson, and Engstrom (1981) report two studies, using subjects within the normal range of ability in which recency and primacy recall were comparably correlated with intelligence. However, their STM task was some- what different to that used by Cohen and Sandberg. Primacy and recency scores from the free recall of words lists, presented at the rate of one word every two seconds, were correlated with fluid and crystallized intelligence tasks. Horn et al. 's task, using words rather than digits as items, and with a relatively slow presentation rate, would be expected to allow greater subject variation in the use of executive or control processes. This might account for the higher pri- macy-intelligence correlations found by Horn et al., compared with the results of Cohen and Sandberg.
Aims of This Study
Our study was designed to investigate further the relationships between recen- cy and primacy recall in tasks similar to those used by Cohen and Sandberg (1977, 1980) and performance on intellective cognitive tasks. Its main aim was to extend findings beyond those involving global measures of intelligence, as used in the above studies. The present test battery contains markers for fluid and crystallized intelligence as defined, for example, in Horn (1980). Cognitive speed measures were also included. Speed and accuracy (or ~'power") measures of intelligence have been shown to form reliably distinct and lowly correlated factors (see Horn, 1980; Horn & Bramble, 1967). As it can be assumed that the global IQ measures used by Cohen and Sandberg would contain both speed and power components, it is therefore of interest to investigate the separate correla- tions of primacy and recency recall with these ability components. Also the range of memory variables was extended to include both of the different experimental paradigms used in the above two studies to obtain recency and primacy scores, as
Gf/Gc AND PRIMACY/RECENCY 229
well as additional variables which might assist in the theoretical interpretation of the results.
In addition, six tests of the Temporal Tracking primary factor (Tc; see Stankov & Horn, 1980) were also included. This latter factor has become a marker for fluid intelligence (see Horn & Stankov, 1982; Stankov, 1978, 1980, 1983), although it also has some common variance with the broad auditory perceptual factor, Ga. One reason for including a Temporal Tracking marker in our battery stems from the interpretation of this factor. Although there are several possibilities in this regard (see Stankov & Horn, 1980), the preferred description of the processes tapped was in terms of "working memory" (Stankov, 1983). This means that performance of this factor can be best understood in terms of those aspects of the human information processing system which are used to do something with immediately available information. Since the processes of rehear- sal and short-term storage and retrieval can be assumed to be involved in the performance of memory tests and, by definition, in the concept of "working memory," it was important to include markers of the Temporal Tracking prima- ry in our battery.
Our memory variables include primacy and recency measures derived from both free and probed-recall tasks. Previous studies on the relationship between recency recall, primacy recall, and intelligence have typically used only a single experimental paradigm in obtaining these recall measures. The results of Horn et al. (1981) and those of Cohen and Sandberg (1977, 1980) are in only limited agreement. The former study, however, used free recall procedures with lists of words for obtaining recency and primacy scores, while the latter used probed, ordered recall of digits. Cohen and Sandberg's primacy measures were much less related to intelligence than were their recency measures. This was not repeated in Horn's results, where both recency and primacy showed comparable correlations with intelligence, although there was a slight tendency for recency recall to be associated more with fluid intelligence and primacy recall more with crystallized intelligence. Although, as discussed earlier, such lack of agreement might be expected to result from differences in rate of presentation and item content, it is not apparent whether this might not be due to differences in subjects, to the factorial composition of their intelligence measures, or to their use of different experimental paradigms for obtaining recency and primacy scores. We have included in our battery recency and primacy measures obtained from both free and probed recall tasks in order that this might be further investigated.
A delayed recall task was included among our memory variables. This task was thought to be of theoretical interest for the following reason. Some authors (see Horn, 1977) have suggested that recency recall should be regarded not so much as an aspect of memory, but as an output of the current contents of awareness. This is in accord with an interpretation of recency recall as output from Primary Memory, if the term "Primary Memory" is used in William
230 CRAWFORD AND STANKOV
James's original sense as containing the span of immediate apprehension, or consciousness. A delayed recall task, with an attention-distracting filler, was included in our battery. This provided a conceptually opposite measure to recen- cy, in the sense that it represents the ability to retrieve items which have tem- porarily left the focus of attention. Primacy measures might also be given this interpretation, but it was thought that delayed recall provides a more extreme and clear contrast.
Within the psychometric domain it was expected that three broad, second- order factors (fluid and crystallized intelligence and broad speediness) would be obtained. It was expected that these would be formed from the primary factors, Induction, Verbal Comprehension, Cognitive Speed, and Temporal Tracking. From among these primary factors Induction, and particularly Temporal Track- ing, should show the highest correlations with the memory variables. The memo- ry variables, on the other hand, should form two basic clusters--primacy and recency--if the cross-situational constancy of these constructs is to hold. Al- though recency and primacy variables might be expected to exhibit different patterns of correlation with other variables, it was anticipated that all STM tasks would correlate more strongly among themselves than with our psychometric variables. It has been consistently found (e.g., Horn, 1977) that both recency and primacy measures each have their major loading on a single factor (SAR), although they also share some variance with fluid and crystallized intelligence. In accordance with Cohen and Sandberg's (1977) findings, recency measures from our probed-recall tasks should have higher correlations with the Verbal Comprehension or Induction factors. (These latter two factors might be expected to best represent, in our study, the global measure of intelligence used by these authors.) The results of Horn et al. (1981) suggest also that our free-recall primacy measure, as well as recency, should correlate with these psychometric measures. However, our rate of presentation (3 words per second) was faster than that used by Horn (1 word per 2 seconds). This rate of presentation was chosen to be the same as for our probed-recall tasks, to allow a more direct comparison of results between the two paradigms. In view of our previous discussion on the role of executive, or control, processes in STM-IQ correla- tions, therefore, it is possible that our free recall primacy, but not recency, measures may show decreased correlations with intelligence, compared to those obtained by Horn et al. (1981).
METHOD
Subjects
These consisted of 83 Psychology I students at the University of Sydney who were required to complete a total of 5 hours as subjects for research. The mean age was 23.6 years, range 18 to 36, with 83% of subjects between 19 and 21
Gf/Gc AND PRIMACY/RECENCY 231
years. The sample would be expected to have higher averages, and smaller variations in abilities related to academic success than would a sample randomly selected from the general population.
Procedure
A battery of 18 tests was presented to groups of subjects in two sessions, each separated from the next by at least one week. The groups varied from 4 to 20 subjects. Total testing time for each subject was about 43/4 hours, and was divided approximately equally between the two sessions. The order of presenta- tion of tests remained constant and is displayed in Table 1. Tests requiring auditory presentation were given via a cassette tape deck (Sony TC192), ampli- fier (Sony TA70), and loudspeaker (Sony SP620).
The Tests
The 18 tests and the 27 variables derived from the tests are listed in Table 1. Most tests were used previously in work by Horn (1980) and Stankov and Horn (1980). Tests called Sets and Substitutions and memory variables (18-25) were constructed by the authors and are used for the first time in this study.
For some tests, as indicated below, speed measures were also obtained in the following way. At half-minute intervals, signals of "tick-now" were given via the loudspeaker and subjects were instructed to tick the question they were currently solving. Subjects were also instructed to always work forward through the test, and after attempting the last item to stop. The speed score consisted of the total number of ticks with the sign reversed. All subjects were allowed sufficient time to complete all questions, although instructions were to work as quickly and accurately as possible.
Synonyms
For each item a word was spoken twice. The subject's task was to write down as many words as possible which have the same, or nearly the same, meaning as the given word. Spelling was not important. Subjects were told that points would be awarded, not only for the number of words written, but also for how close their meanings were to the given word. Twenty seconds were allowed for each item.
Scoring: Variable 1 = Total number of words judged "correct" by a pro- fessional teacher of English
Esoteric Analogies
For each item three words were written. The subject was instructed to choose from four alternatives the word which had the same relationship to the third word as the second does to the first.
For each item the subject was presented with a two-dimensional array of figures with one missing. The subject had to choose from five alternatives the figure which would complete the pattern.
For each item two sets of three letters were spoken with a pause separating the sets. Subjects were instructed to write the letter which occurred only in the first set, and then the letter which occurred only in the second set. They were allowed 5 seconds to respond to each item.
Two sets of three letters were spoken with a pause separating the sets, and followed by a further three letters, spoken slowly at 4 seconds per letter. These
Gf/Gc AND PRIMACY/RECENCY 233
last three letters were also contained in the first set, though not necessarily in the same order. The subject had to write down the letters in the second set which were in the same position, in the first set, as were the slowly spoken letters.
Example: yxz, gpt; x; y; z (Correct response: p, g, t) Scoring: Variable 13 = Number correct
Letter Reordering
Two sets of three letters, each composed of the letters r, s, and t were spoken. The subject had to indicate, by means of writing the digits 1, 2, 3 in the appropriate order, the way in which the second set was reordered relative to the first.
Example: RST, TSR (Correct response: 321) Scoring: Variable 14 = Number correct
Tonal Reordering
Same as Letter Reordering, except instead of the letters R,S,T, the musical notes middle-C,E,G were used.
Scoring: Variable 15 = Number correct
R.S.T. Task
Lists of letters of lengths 6, 7, and 8 were presented at a rate of one per second. Lists contained varying numbers of each of the letters. When each list had ended, the letters R, S, and T were spoken slowly, in that order, and subjects had to write down the number of times each letter had occurred in the preceding list.
Example: R S S T R T S: R, S, T. (Correct response: 2, 3,~2) Scoring: Variable 16 = Total number of letter counts correct
Do-Mi-So Task
Same as above, only the muscial notes middle-C, E, and G were used instead of letters R, S, T.
Scoring: Variable 17 = Total number of tone counts correct
POIR (Digits) (Probed, Ordered, Immediate Recall)
Each item consisted of the words " f i r s t " or " l a s t " followed by a list of random digits spoken at about 3 per second. The lists were of spoken lengths 12,
234 CRAWFORD AND STANKOV
15, or 18 digits, and these lengths were presented in random order. The instruc- tions were as follows. If the word "f i rs t" was spoken, the beginning of the list was "more important," and the subject had to write down as many digits from the beginning of the list, in their correct order, as possible. Then, as many digits from the end of the list were to be written, again in their correct order. If the word " las t" was heard, then the end of the list was "more important," and the subject had to do as above, only in the reverse order. Subjects were instructed not to guess, but rather to leave a position blank if uncertain of a digit. Five boxes at the beginning and four at the end were provided on the response sheet (see below) to guide the positioning of responses.
Example: First 192763184218
TypicalAnswer: 111912[71316 [ i2l 11181 Scoring: Variable 18 = (Primacy Measure). Number of correct digits in correct positions, from first five positions for items commencing with the word "first." Variable 22 = (Recency Measure). Number of correct digits from the last four positions, in correct positions for items commencing with the word "last."
POIR (Letters)
Same as for POIR (Digits), only using list lengths 9, 12, 15, and letters instead of digits.
Scoring: Variable 19 = (Primacy Measure). As above; Variable 23 = (Re- cency Measure). As above.
PODR (Digits) (Probed, Ordered, Delayed Recall)
Same as for Test 15, except that following each list of digits, four three-letter words were spoken at four-second intervals. The subject had to write each of these words backwards as they were spoken. Also, the cues "f i rs t" or " las t" came at the end of the list.
Example: 731862459312 dog, cat, hat, fin; first Scoring: Variable 20 = (Primacy Measure). As for Variable 18. Variable 24 = As for Recency Measure of Variable 22.
Free Recall (Words)
For each item a list of words (lengths 12, 15, or 18) were spoken at a rate of about three per second. Subjects were instructed to write as many of the words as they could as soon as each list had ended. Subjects were told that spelling wa~, not important, and that they could write the words in any order they wished.
Gf/Gc AND PRIMACY/RECENCY 235
Scoring: Variable 21 = Number of words recalled from first six of each list; Variable 25 = Number of words recalled from last three of each list.
Forward Digit Span
Forty lists of random digits (1 to 9) with lengths varying from 6 to 10 digits were presented at a rate of two per second. The various lengths came in random order with eight lists each of lengths 6, 7, 8, 9, and 10 digits. Subjects were instructed to write down, as soon as each list had ended, the list in the original order.
Scoring: Variable 26 -- Number of lists correct
Backward Digit Span
Same as above, except that lists varied from 3 to 7 digits in length, and subjects were instructed to write down the list backward, writing down first the last digit, then the second-last, etc.
Scoring: Variable 27 = Number of items correct
Statistical Analysis
For purposes of analysis we have divided our 27 variables into two sets. The first 17 we shall call the "Psychometric Variables" as they represent markers for several well-established cognitive ability factors. The remaining variables we shall term the "Memory Variables" since they represent various aspects of short-term memory performance. Factor analyses were carried out using the Little Jiffy Mark IV package of Kaiser and Rice (1974).
RESULTS
Factor Structure Among the Psychometric Variables
The essential descriptive statistics regarding all variables used in this study are presented in Tables 1, 2, and 4. In Table 1, it can be noted that primacy and recency scores based on the free recall task (Variables 21 and 25) have a rather low split-half reliability. This should reflect upon the correlations which these measures have with other variables in the battery. While inspecting the correla- tions presented in Table 2, it should be kept in mind that the signs for all coefficients involving speed scores (Variables 4 -8 ) have been reversed.
The correlational matrix of Table 2 was factor analysed and the resulting solution was rotated using image-analysis and orthoblique rotations embodied in the Little Jiffy, Mark IV package. This produced five first-order factors. Factor intercorrelations were then subjected to the same procedures and three second-
236 CRAWFORD AND STANKOV
TABLE 1 Descriptive Statistics For Variables Used in This Study
Order No. of Variable a of Presentation b Items X s rtt
aPOIR = Probed, ordered, immediate recall; PODR = Probed, ordered, delayed recall. bA = first session; B = second session (a week afterward).
order factors were ext rac ted . The hierarchical solut ion presen ted in Table 3 was
obta ined in accordance wi th the me thod descr ibed by Stankov (1979). All values
above .20 in this table are italicized.
The above results may be easi ly in terpreted by reference to previous work
associa ted with the Horn-Cat te l l theory o f fluid and crystal l ized intel l igence (see,
for exam p le , Horn, 1980; Stankov & Horn, 1980). W e shall cons ider firstly the
five factors p roduced in the f i rs t -order solution. The first o f these factors we have
label led Verbal C o m p r e h e n s i o n (V). Howeve r , each of the tests marking this
factor ( S y n o n y m s , Word Mean ings , and Esoter ic Analogies) would , in a larger
battery o f tes ts , be markers for the es tabl ished pr imary factors Associa t ional
F luency , Verbal C o m p r e h e n s i o n , and Cogni t ion o f Semant ic Relat ions , respec-
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38
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238 CRAWFORD AND STANKOV
tively. This factor, then, might be more directly compared, in terms of breadth of content, to the second-order factor of crystallized intelligence in Gf/Gc theory. We have called this factor Verbal Comprehension, however, to indicate that it was obtained at the first level of factoring.
Similarly, the third factor, labelled Induction (I), was marked by tests (Letter and Figure Series, Cattell's Matrices, and the RST Task) which have been found to be markers for the primary factors Induction, Cognition of Figural Relations, and Temporal Tracking. This factor therefore is comparable in scope to the second-order fluid intelligence factor in Gf/Gc theory. Again, we have labeled it Induction, rather than fluid intelligence, to indicate that it was formed at the first- order stage of analysis in this study.
The second first-order factor is a well-defined Cognitive Speed (Sp) primary in this data. This factor should be distinguished from the clerical or perceptual speed abilities, such as are involved in the Gs factor discussed by Horn (1980). Our Cognitive Speed factor rather should be compared with the Correct and Wrong Decision Speed factors of Horn, and possibly also Carefulness and Per- sistence. This is because our speed scores do not distinguish between the time taken to make correct and incorrect responses, but measure simply the rate at which a subject proceeds through test items, when instructed to work as quickly and accurately as possible.
The last two first-order factors we have called Temporal Tracking (Letters), Tc(L), and Temporal Tracking (Tones), Tc(T). In previous work a single Tem- poral Tracking factor, Tc, was formed by tests similar to those of this study. However, the occurrence here of two separate Tc factors, divided on the basis of item content, is understandable. Firstly, most of the earlier studies which yielded a single Tc factor contained tasks involving tones (and other auditory stimuli) but not letters (e.g., Stankov & Horn, 1980). At the second level of factoring, the Tc factor, defined in this way, was found in these studies to contain considerable variance in common with the broad auditory factor Ga, defined by short-term memory for sequences of tones and other auditory stimuli (Horn & Stankov, 1982). Second, in one study (Stankov & Spilsbury, 1978), Tc tasks involving tones and also letters were included. A single Tc factor did emerge, but the test involving letters (Letter Reordering) loaded even more heavily on a memory span factor, Msa, than it did on Tc. From the above it appears that the Tc factor contains at least some variance in common with abilities involving short-term memory for the sorts of items contained in the particular Tc tasks. It is important to note here that short-term memory for auditory sequences of letters, and short- term memory for sequences of tones, are associated with distinct ability factors, both at the first and second level of factoring. (Msa and SAR factors for letters; DASP and Ga factors for tones, respectively; see Stankov & Horn, 1980; Horn, 1977). We therefore have interpreted the formation of separate Tc(L) and Tc(T) factors in this study as being due to Tc(L) containing some component of Msa
Gf/Gc AND PRIMACY/RECENCY 239
(or SAR) ability, and Tc(T) containing instead some component of DASP (or Ga) ability, l
We will now consider the second-order solution shown in Table 3. Hierarchi- cal solutions of the kind presented here typically produce factors which, at the second-order, have noteworthy loadings from a relatively larger set of variables; that is, they are broader in scope. The finding that the first second-order factor (labelled crystallized intelligence, Gc) and the first first-order factor (Verbal Comprehension, V) had the same breadth is unusual. We have used different labels in order to indicate that although they appear at different levels of factor- ing, they appear to have the same interpretation. The other two second-order factors, however, do have a broader scope.
The second second-order factor, labeled General Speed, Gs, is slightly broad- er than the first-order speed factor, Sp. Its highest loadings are from those variables defining the Sp factor at the first order, but it also contains lower positive loadings from Tc(L) tasks and small negative ones from tasks defining the first-order factor, I.
The third second-order factor is defined by variables from the three primaries I, Tc(L), and Tc(T). As discussed earlier, variables defining the first of these, Induction, have in previous work, been closely linked to the second-order fluid intelligence factor, Gf. Also, the primary factor Tc has been found to define, in part, Gf (see Horn & Stankov, 1982). We have therefore labeled our third second-order factor fluid intelligence, Gf. However, caution is needed when comparing our Gf factor, in terms of ability content or construct validity, to the fluid intelligence factor, as it is traditionally defined within the Horn-Cattell theory of fluid and crystallized intelligence. In previous work within the Gf/Gc framework (e.g., Horn & Stankov, 1982), Tc has been found to load not only on Gf but also the auditory factor, Ga. Moreover, it is also likely, as discussed earlier, that those Tc tasks in this study, involving letters, would share compara- ble variance with the short-term memory factor, Msa (or SAR). Our third sec- ond-order factor could therefore be interpreted, in terms of the second-order
i .
ability structure of Gf/Gc theory, as some unknown combination of Gf, Ga and SAR factors.
In view of this lack of clarity in relating our second-order Gf factor to estab- lish abilities, only the first-order solution will be used for further analysis. Also, to avoid ambiguity, "fluid intelligence" (Gf), in further discussion will refer, not to our second-order factor of that name, but to the concept embodied in
IThis interpretation is partially confirmed by some results not reported here. The psychometric variables, together with Forward and Backward Digit Span tests were factor analyzed. It was found that the Tc tasks involving letters, but not those involving tones, loaded on a factor defined by the two memory-span tests.
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55
-0
5
-06
-1
2
57
5.
Spe
ed (
Wor
d M
ean
ing
s)
-21
22
-
12
-41
16
-
16
-05
06
42
6.
Spe
ed (
Let
ter
Ser
ies)
-0
8
40
-02
-0
7
49
09
01
-06
44
7.
S
peed
(F
igur
e S
erie
s)
-08
41
08
-l
0
34
-07
-0
7
18
44
8.
Spe
ed (
Mat
rice
s)
-ll
43
05
-08
51
05
06
13
53
9.
L
ette
r S
erie
s 07
-
13
37
09
- l
I 29
l0
03
38
10
. F
igur
e S
erie
s -0
2
-24
45
-0
3
-02
55
-0
3
-07
47
11.
Mat
rice
s -0
1
-22
42
03
-0
2
44
-08
04
40
12
. S
ets
07
28
18
-03
-0
2
-06
45
-0
1
53
13.
Sub
stit
utio
ns
04
22
23
-09
-0
3
02
42
-04
49
14.
Let
ter
Reo
rder
ing
04
20
30
08
07
ll
28
06
52
15.
Ton
al R
eord
erin
g -0
2
06
40
09
-02
-0
1
-01
45
44
16
. R
ST
Tas
k
00
05
45
02
12
35
09
09
52
17.
Do-
Mi-
So
Tas
k
-03
04
43
01
-0
5
-02
-0
1
49
53
aDec
imal
poi
nts
omit
ted;
R 2
=
squa
red
mu
ltip
le c
orre
lati
on.
bSec
ond-
orde
r fa
ctor
s ar
e: G
c =
cr
yst
alli
zed
inte
llig
ence
; Gs
=
broa
d sp
eedi
ness
; G
f =
fl
uid
inte
llig
ence
. cF
irst
-ord
er f
acto
rs a
re:
V
=
Ver
bal
Com
preh
ensi
on;
Sp
=
Co
gn
itiv
e sp
eed;
I
=
Indu
ctio
n; T
c(L
) =
T
empo
ral
Tra
ckin
g
(Let
ters
); T
c(T
) =
T
empo
ral
Tra
ckin
g (
Ton
es).
Gf/Gc AND PRIMACY/RECENCY 241
Gf /Gc theory. For reasons outlined above, our first-order Induction factor could be regarded as an appropriate representation of Gf.
Another reason for restricting ourselves to the first-order solution derives from our previously stated intention to extent the present findings beyond the global second-order measures of intelligence. This will provide a finer-grained analysis than would be obtained by considering the second-order factors only. In the present situation this approach is also suggested by the fact that Tonal and Letter Temporal Tracking factors involve processes previously discussed under the label of working memory. This latter notion has an interesting theoretical relationship to memory span which global fluid intelligence measure would not be able to disclose.
Structure Among the Memory Variables
Table 4 contains correlations among all ten memory variables used in this study. It can be noted that the two variables showing a negative correlation are also those with low reliability (primacy and recency measures obtained from the free-recall task). Since positive manifold among cognitive tasks is such a well- established finding, the present results suggest a cautious interpretation of cor- relations involving free-recall measures. Low reliability, in particular, points to the possibil i ty that relatively unstructured conditions of the free-recall task has led to an increase in error of measurement. Because of this possibility, Variables 21 and 25 were excluded from the analyses intended to establish the structure among memory variables.
We might mention, however, the possibili ty that the negative correlation of - . 2 9 between primacy and recency in free-call may be the result of subjects trading off pr imacy against recency recall, since both of these measures were obtained from recall of the same lists. Since primacy and recency scores from all
probed recall tasks are positively correlated, this would support Wickelgren's (1975) opinion that primacy/recency recall from free and probed recall tasks cannot be assumed to represent the same cognitive mechanisms. While acknowl- edging the low reliabilities of our free recall measures, our data do seem to support his contention that response interference is an important mechanism in determining free, but not probed, recall measures.
Factor pattern matrices obtained from correlations presented in Table 4 are given in Table 5. In order to provide an answer to the question of whether primacy and recency measures from different probed recall tasks define the same factors, the first solution of Table 5 was obtained by omitting Forward and Backward Digit Span tests from the analysis. It can be ascertained from this that primacy and recency measures do indeed define two separate factors, and this implies that these two sets of variables represent distinct processes in individual differences.
The second factor pattern matrix of Table 5 was obtained in order to find out what is the relationship between primacy and recency scores and traditional measures of Memory Span (Variables 26 and 27). There are two things to be noted. First, Forward and Backward Digit Span tests define the same factor. This is a typical finding in studies involving these two measures which is interesting because Jensen and Figueroa (1975) have reported that Backward Digit Span has a higher correlation with measures of intelligence than does the Foward Digit Span test. Factor I has a salient loading from only one memory variable, the primacy measure of delayed recall (Variable 20). The other two primacy mea- sures have some, admittedly nonsalient, loadings on this factor. The suggestion is that Memory Span variables tap the same processes as those of primacy measures and, in particular, those of the delayed recall task. By contrast, Horn
TABLE 5 Factor Pattern Matrices for Memory Variables Presented in Table 4
.41 c -.11 .16 .78 c -.33 .36 -.10 .53 c .27 -.10 .63 c .40
.15 .35 c .29 .10 .42 c .33 -.02 .42 c .22 .19 .30 .26 - - - - - - .59 c .13 .57 - - - - - - . 6 5 ~ .03 .50
.81 .78
aVariables 21 and 25 not included. bSMC = squared multiple correlation.
Gf/Gc AND PRIMACY/RECENCY 243
(1980) found that both primacy and recency measures have loadings on a factor defined mainly by the Memory Span tests. However, he used the free-recall memory task which, in this study, has low reliability. The second point to be noted is that the clear separation of primacy and recency factors has been lost by the inclusion of the digit span tests. Factor II has some resemblance to recency and Factor I to primacy but, if one accepts Little Jiffy's criteria for salience, the similarity between the two solutions of Table 5 is not strong.
Correlations Between the Psychometric and Memory Variables
Correlations between the memory variables and the first-order psychometric factors are shown in Table 6. Primacy and Recency factor scores, derived from the first solution of Table 5, were correlated with the psychometric factors. These correlations are also displayed in Table 6.
From these results it can be seen that, for the probed recall tasks, recency measures have consistently higher correlations with the 1 and V factors than do the primacy measures. This is partially reflected in the correlations of the Pri- macy factor (r = .22) and the Recency factor (r = .31) with Induction, I. These results reflect the trend, to some extent, in the studies of Cohen and Sandberg (1977) who found that recency recall, from probed recall tasks, is more closely related to IQ than is primacy recall. (Their IQ measure can be assumed to correspond to some combination of our I and V factors.) However, the pattern in
TABLE 6 Correlations of 1st Order Psychometric Factors with Memory Variables and Memory Factors
bDecimal points omitted. ~Factor scores obtained from the 1st Solution of Table 5.
Induction; Tc(L) =
244 CRAWFORD AND STANKOV
our results is much weaker than that observed by Cohen and Sandberg. They obtained near zero correlations of primacy recall with IQ, but correlations be- tween recency recall and IQ frequently above .6. A possible explanation for this difference will be suggested later in this paper.
The highest correlations in Table 6, however, are between the memory vari- ables and the two Temporal Tracking factors, Tc(L) and Tc(T). These correla- tions reflect, in part, the common influence of fluid intelligence, best represented in this study by the Induction factor, I, in both measures. The consistent relation of short-term memory and Temporal Tracking variables with fluid intelligence is well established (see Horn & Stankov, 1982). However, the considerably higher correlations of these Tc factors with the memory variables, compared with those between the memory variables and I, suggest a more direct link. It was pointed out earlier than Temporal Tracking tasks, as well as helping define fluid intel- ligence, also share considerable variance with abilities associated with short-term memory for items involved in the particular Tc task. In terms of the second-order abilities described in Gf/Gc theory, it is likely that our Tc(L) factor contains substantial contributions of both Gf and SAR abilities, while our Tc(T) factor contains both Gf and Ga abilities. The higher correlations of the memory vari- ables with the Tc factors, than with I, can therefore be explained as resulting from the direct associations between the memory variables and the SAR or Ga dimensions, independent of the common influence of Gf.
The above interpretation also accounts for the consistently higher correlations of the Tc(L) factor, compared with those of the Tc(T) factor with the memory variables. Our memory variables, involving numbers, letters and words are directly linked to the definition of SAR. Ga, on the other hand, defined by the short-term memory for tones (and other sound patterns) is thus less closely linked with our memory variables. It is important to note, however, that short-term memory for tones, and for letters, digits, etc., although defining separate ability factors, are nonetheless positively correlated (see Stankov & Horn, 1980).
An interesting new outcome has been obtained in correlations between the measures of speed in working through the intellective test items (Cognitive Speed Factor) and probed-recall memory variables. Contrary to the findings with intelligence factors, Cognitive Speed is more related to primacy measures from probed-recall tasks than it is to recency.
As mentioned above, our free-recall recency and primacy measures gave reliability estimates which are rather low. Our results involving these measures should thus be viewed with caution. However, we might briefly note one aspect of our results which serves to illustrate a point made earlier. Despite their low reliabilities, our free recall recency measures supported correlations with Verbal Comprehension and Induction (r= .31 and .22, respectively) which are similar to (and even slightly higher, on average) than those corresponding correlations with crystallized and fluid intelligence reported by Horn et al. (1981). Our primacy scores, on the other hand were correlated less with intelligence, com-
Gf/Gc AND PRIMACY/RECENCY 245
pared to both our recency-intelligence correlations and the primacy-intelligence correlations reported by Horn. This is indeed what would be expected to result from our use of a very rapid rate of item presentation, if it is assumed that limiting the possibility of significant individual differences in mnemonic strat- egies would lower correlations with intelligence. Although Lyon (1977) present- ed evidence that such strategies were not related to individual differences in digit-span performance, it is possible that they may play a more significant role in the less restrained free recall task which uses more '~meaningful" words, rather than digits, as items.
From our data we may also compare the correlations of Forward and Back- ward Digit Span with various psychometric factors. This is of some interest, in view of the theoretical importance given by Jensen to his finding that Backward Digit Span correlated more with intelligence than Forward Digit Span (Jensen & Figueroa, 1975). Our data show that both these span measures correlate equally with Verbal Comprehension (r = . 19), but that Forward Digit Span correlates slightly more with Induction (r = .30) than does Backward Digit Span (r = .24). There is, however, a larger difference between Forward and Backward Digit Span tests in their correlations with our Cognitive Speed factor (r = . 18 and .29, respectively). We may therefore interpret our findings as compatible with those of Jensen and Figueroa, only if we assume that their intelligence measure reflects a significant proportion of capacities tapped by our Cognitive Speed factor. If this is so, however, the theoretical relevance of their finding as providing confirmation of a prediction based on Jensen's Level 1/ll theory of intelligence, may be questioned. This is especially so in view of Horn's (1980) evaluation of Cognitive Speed as being reliably distinct from, and lowly corre- lated with, accuracy, or power, measures of intelligence. We might note here that Forward and Backward Digit Span have been found in previous studies to be highly correlated with each other and to define the same primary factor (e.g., see Stankov, Horn, & Roy, 1980).
DISCUSSION
The formulation of an adequate explanation of the relationship between intel- ligence and recency and primacy recall is made difficult by the lack of agreement in the empirical evidence. Apparently reliable studies have suggested that intel- ligence is related to recency, but not primacy recall (Cohen & Sandberg, 1977), to primacy but not recency recall (Ellis, 1970; Ellis, McCarver, & Ashurst, 1970), and to both primacy and recency recall (Cohen & Nealon, 1979; Horn et al., 1981; and the results of this study). It would be wrong, however, to regard these results as directly contradictory. Recency and primacy measures in these studies were obtained from a number of different experimental paradigms (free recall of words, paired associate recall, probed serial recall of digits, etc.), and different studies utilized variation in performances either within or between
246 CRAWFORD AND STANKOV
groups of normals and retardates, some studies using children and others using adults as subjects.
Currently two explanations of such data are being proposed. One explanation links intelligence with individual differences in the use of executive or control functions such as rehearsal. This explanation, as proposed by Ellis (1970) and Ellis et al. (1970), accounts for those data which show a significant primacy, but not recency, link with intelligence. However, it is unable to explain the results of other studies which have yielded significant recency-intelligence correlations, especially when smaller, or negligible, primacy-intelligence correlations were also found, as in Cohen and Sandberg's (1977) work.
The second explanation, proposed by Cohen and Sandberg (1980), suggests that it is the "encoding of items-in-order" under memory load which is the process linked with intelligence. Recency items are encoded under the memory load of items earlier in the list, while primacy items are encoded with little or no memory load. Thus it is predicted that recency, but not primacy, recall is corre- lated with intelligence. This latter explanation does not, however, allow for data in which significant primacy-intelligence correlations are found together with smaller recency-intelligence correlations.
Proponents of both of the above explanations have adopted as a theoretical framework a multistore model of memory. We suggest that their failures to account for the full range of experimental data, in which either, or both, of recency and primacy recall is correlated with intelligence, results from over- simplified applications of the multistore model. We shall start with the explana- tion offered by Ellis (1970) and suggest modifications which might allow the multistore approach to apply to data in apparent conflict with that discussed by Ellis (1970) and Ellis et al. (1970).
The explanation suggested by Ellis utilizes a two-stage model of memory similar to that proposed by Waugh and Norman (1965) and Broadbent (1958). Information is first received into Primary Memory which is a transient, limited capacity store. It is rapidly lost from this store unless it is encoded into a more stable Secondary Memory system. The rate of transfer to this Secondary Memory system is assumed to depend on the efficiency of rehearsal and other "control" or "executive" strategies. It is further assumed that intelligence, as defined by standard test batteries, is linked with the performance of these control processes, while the properties of the Primary and Secondary Memory systems themselves are assumed not to be related to intelligence. Recency recall, it is argued, results from retrieval from Primary Memory and is not related to intelligence. Primacy recall, however, resulting from retrieval from Secondary Memory, is a function of the rate of transfer of items from Primary to Secondary Memory. Since this transfer is facilitated by the efficient use of control processes, primacy recall is linked with intelligence.
There are several assumptions in the above account which might be ques- tioned. The first is that Primary Memory is "'sensory" in nature (Ellis et al.,
Gf/Gc AND PRIMACY/RECENCY 247
1970) and is thus not expected to be related to intelligence. Multistore models, such as Atkinson and Shiffrin's (1968) model, have distinguished two such short-term transient memory systems. The first is a number of modality-specific Sensory Registers (SR's) and the second is what these authors have termed the Short-Term Store (STS). From the description of the operation of these two stores in their model, it must be presumed that Primary Memory, as the term is used by Ellis (1970) represents the combined storage functions of the SR's and the STS. While the SR's, being "sensory" in nature might be expected to bear little relation to intelligence, this is not true of the STS. In Atkinson and Shiffrin's model, the STS not only has a storage function, but operates as a sort of general purpose central processor. It is the system within which rehearsal and other such control processes are postulated to take place, and so is a memory system the properties of which might be expected to be most closely associated with intelligence.
Significant recency-intelligence correlations therefore become less surprising if the purely sensory nature of Primary Memory is rejected. There is, however, another way in which intelligence and recency recall might be related within a multistore model of memory. This involves the possibility that recency recall includes the retrieval of items from Primary Memory, and in addition, items which have recently encoded into Secondary Memory (see Bernbach, 1975). In Ellis's model this was not considered, presumably since the data being explained show no relationship between recency and intelligence. It may, however, be relevant to the explaining of other data which do show significant correlations between intelligence and recency recall.
In the model proposed by Ellis, individual differences in primacy recall are thought to reflect mainly individual differences in the control processes which facilitate the transfer of items from the Primary to the more stable Secondary Memory system. However, this ignores the possible importance of what we shall term the passive holding ability of Secondary Memory. By this term we mean the resistance of decay of items in Secondary Memory in the absence of reactivation by rehearsal. The recall of items which have been recently encoded, or else subject to frequent rehearsal, would reflect individual differences in control processes. Hence, in agreement with Ellis, the recall of such items may be expected to correlate with intelligence. However, many tasks do not allow the frequent rehearsal of items previously presented. This might be expected, for example, for a delayed recall task with a rehearsal preventing filler during the delay, or else primacy recall from the immediate recall of a fairly long list with fast item presentation rate. For the latter task, the encoding of incoming items would operate, to some extent, to restrict rehearsal of earlier items. Since there is no reason to suppose any strong connection between intelligence and this passive holding ability, recall under such conditions of restricted rehearsal could be expected to yield lower correlations with intelligence. This is reflected in our data by the lower correlations with intelligence of our delayed recall measures
248 CRAWFORD AND STANKOV
(Variables 20 and 24) when compared to the corresponding primacy and recency measures from the immediate recall tasks (Variables 18, 19, 22, 23, see Table 6).
Studies comparing retardates with normals (Ellis, 1970; Cohen & Nealon, 1979) or those comparing groups of retardates of varying mental ability (Ellis et al., 1970) have found significant group differences on primacy recall. However, within groups of 11 and 12-year-old normals, Cohen and Sandberg (1977) ob- served near-zero correlations between intelligence and primacy recall. This dif- ference cannot be attributed to differences in tasks, since the studies of Cohen and Nealon (1979) and Cohen and Sandberg (1977) both used the same probed serial recall of digits paradigm. These results could be accounted for, however, if it is assumed that within groups of normals passive holding ability is not related to intelligence, but that there does exist a significant difference between normals and retardates in passive holding ability. This is consistent with the widespread view that memory span bears a nonlinear relationship with intelligence, being strongly related at the lower levels of ability, but not at the average and above average ranges (see Matarazzo, 1972). An alternative account could be offered in terms of rehearsal strategies. However, the post-cued, probed-recall task, with item presentation rates as fast as 6 or 9 digits per second, used by Cohen and Sandberg, would make rehearsal of prior items highly unlikely, for both normals and retardates. Moreover, the account in terms of passive holding ability seems to be a desirable alternative to that in terms of rehearsal strategies in view of the mounting evidence that strategic variables are not important in explaining indi- vidual differences in short-term memory (see review by Dempster, 1981; Lyon, 1977).
We may note here that Cohen and Sandberg (1980) suggest a different expla- nation for the lack of correlation, among normals, of primacy recall with intel- ligence. These authors argued that it is "the encoding of items-in-order under memory load" which is the process linked to intelligence. Primacy items, unlike recency items, are encoded under little or no memory load, and so recall of these items is not correlated with intelligence. In contrast, we have suggested that for tasks such as theirs where rehearsal of previously presented items is not possible, primacy recall is a function of the subject's passive holding ability, an ability not closely linked with intelligence for normal subjects. Although both explanations do seem to yield similar predictions, it is possible to discriminate between them. If we consider probed-recall correlations with intelligence for lists of various lengths, Cohen and Sandberg's explanation would predict that these correlations should vary as a function of the distance of the recalled items from the front of the list, while our account suggests that it is the distance from the back of the list which is important. Results reported by Cohen and Sandberg (1977) seem to favor the account in terms of passive holding ability. They found no difference in correlations with intelligence between the probed recall of the last 3 digits for lists of 6 and 9 digits. However, the correlation with intelligence of probed recall
Gf/Gc AND PRIMACY/RECENCY 249
of the middle 3 digits of a 9-digit list was less than that for probed recall of the last 3 digits of a 6-digit list. Cohen and Sandberg would, of course, predict that there should be no difference in these correlations, since in both cases the recalled items, would have been encoded under the equal memory load of the first three items in the list.
For primacy recall, the apparent conflict between various studies was at- tributed to differences in subjects. For recency recall, however, the answer appears to lie in the nature of the tasks. Using probed serial recall of digits, Cohen and Nealon (1979) found that normals and retardates differed significantly on recency recall. Ellis (1970) and Ellis et al. (1970) found no such difference. These latter authors, however, used a paired associate task in which an item was paired with its spatial position. Furthermore, all studies which have shown recency-intelligence correlations have used as items learned symbols such as words (Horn et al., 1981), letters (this study) or digits (Cohen & Sandberg, 1977). Now, Hasher and Zacks (1979) suggested that important differences may exist between processing which is automatic largely as a result of innate factors, such as the encoding of frequencies, spatial location, time of events, and pro- cessing, which is slightly less automatic by virtue of extensive practice, such as the encoding of words, numbers, etc. If we assume, in agreement with Dempster (1981) and Cohen and Sandberg (1980), at least with respect to recency items, that recall-intelligence correlations are a result of individual difference in the encoding of items, then the apparent conflict in results may be resolved. This would require the additional assumption that the encoding of items is related to intelligence only when such encoding is not totally automatic (or slightly effort- ful). Highly automatic encoding, such as spatial location in Ellis's tasks, is thus not related to intelligence. While we have at present no accepted theory which would link effortful processing with intelligence, this does seem to be the only possible explanation of Ellis's (1970) and Ellis et al. 's (1970) failure to find significant differences between retardates and normals on recency recall.
The results of this study and that of Cohen and Sandberg (1977), although similar, do differ in two ways. Firstly, Cohen and Sandberg's recency-intel- ligence correlations, ranging from about .4 to .6 are higher than ours (see Table 6). However, this could be largely due to the subjects used. Cohen and Sandberg used 12- and 13-year-old normals with IQ range approximately 76 to 120. Our study used first-year university students which would probably represent less than half the range in ability of Cohen and Sandberg's sample. Second, in our study the primacy scores of the immediate probed-recall tasks (Variables 18, 19) are correlated with our intelligence factors only slightly less than are the corre- sponding recency measures (Variables 22, 23; see Table 6). However, using a task similar to ours, Cohen and Sandberg (1977) consistently obtained near-zero correlations between intelligence and primacy recall.
We have argued that under the conditions of Cohen and Sandberg's task, that is probed recall with postcueing, rehearsal of primacy items is effectively pre-
250 CRAWFORD AND STANKOV
vented by the need to attend to incoming items. Primacy recall is then a function of passive holding ability and so is not related to intelligence. However, our immediate probed recall tasks were precued. The subject, knowing in advance which items were to be recalled, was able to actively rehearse the primacy items. Primacy recall, under these conditions would be, in part, a function of rehearsal efficiency, and so would be expected to correlate with intelligence. The variable in our study which can be assumed to represent, in its purest form, passive holding ability is the delayed recall, postcued primacy measure, Variable 20. This variable gave correlations with our intelligence factors V and I of .09 and - . 0 2 , respectively.
Our selection of precueing, rather than postcueing, for the probed immediate recall tasks derived from the desire to eliminate any possible complications in the interpretation of recency scores, or their correlations with intelligence, obtained from these tasks. The encoding of a postcue and the subsequent decision pro- cesses, occurring between presentation of the recency items and their recall, could conceivably modify the recency scores. If these tasks were postcued by the auditory words "f i rs t" or " las t , " the existence of the so-called "suffix effect" (Crowder, 1978) would imply that recency recall would be modified by post- cueing.
Intelligence and short-term memory have been conceptually linked via the notion of Working Memory (WM). Baddeley and Hitch (1974) demonstrated the existence of a trade-off between the ability to hold several items in short-term memory and the simultaneous performance of problem solving tasks. The notion of WM was invoked to signify the unity, demonstrated by this trade-off, between short-term storage and the processing functions of the cognitive system. For those interested in human abilities, the question arises as to what extent the concept of WM is reflected in individual differences. For example, Stankov (1983) has suggested that a Temporal Tracking factor could be interpreted as reflecting the functioning of WM.
We suggest, however, that in order to understand the relationship between WM and intelligence, it is useful to make a distinction between what we shall call the active and passive processes of WM. In terms of the model of Atkinson and Shiffrin (1968), active processes are those which involve the Short-Term Store (or central processor) component, while passive processes are those which reflect the properties of the remainder of the memory system such as capacities and decay rates of the Sensory Registers or Secondary Memory. This distinction is similar to, but more general than, the distinction made by Ellis (1970) or Hunt (1978) between the control processes, which govern subjects' strategies, and the "structural" properties of the memory system. Active processes refer to control processes such as rehearsal, but may also include such processes as the encoding of certain items, even in situations where little or no opportunity for variation in subjects' strategies is possible. Thus the encoding of items, suggested by Demps- ter (1981) and Cohen and Sandberg (1980), as underlying correlations between
Gf/Gc AND PRIMACY/RECENCY 251
short-term memory and intel l igence could be classified as involving the active processing of these i tems but was not regarded by these authors as reflecting control of strategic variables. The c o m m o n link between strategic and non- strategic active processes is the invo lvement of the Short-Term Store which gives rise to correlations with intel l igence.
The signif icance of the new finding of this study, that primacy recall is more closely associated with Cogni t ive Speed than recency recall, is not clear. If it is assumed, as Ellis and others have, that pr imacy recall is l inked with rehearsal proficiency, then this result could easily be explained by supposing that subjects high on Cogni t ive Speed are able to rehearse more quickly. However, if for the tasks used in this study (particularly for the postcued delayed recall task) it is thought that pr imacy recall reflects mainly passive holding ability, an alternative explanat ion is required. A possible explanat ion is that those who are low on passive holding abil i ty need to work slower through problems, because they need to more frequently rehearse and consolidate information. They would thus work more slowly, but not necessari ly less accurately, if the extra time spent on consolidat ing memory traces could compensate for their lack of passive holding
ability.
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