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Association and categorisation effects on free recall
Acta Psychologica
37 (1973)
ASSOCIATION
65-77.
0 North-Holland
Publishing
AND CATEGORISATION FREE RECALL
Company
EFFECTS ON
W.A.MATTHEWS Department
of Psychology,
Accepted
University of Southampton,
November
U.K.
1, 1972
Lists of 18 words which varied in mean associative strength, the category membership of the associations and in word frequency were presented to subjects 3 times with recall required after each presentation. Recall efficiency increased with association level and with similarly categorised associates. In lists of high mean associative strength which consisted of similarly categorised words, the recall of high frequency word lists was facilitated but at low levels of associative strength, with similarly categorised words, recall was facilitated at both levels of word frequency used. Clustering and errors which were associatively related to the items being learned were greater in lists which contained sets of similarly categorised associates.
It has been reliably demonstrated that the free recall of word lists increases with the strength of the associations between the individual words (e.g. Deese, 1959; Matthews, 1966). Facilitation of recall also increases when the words making up the list can be grouped into clearly defined categories (e.g. Bousfield, 1953; Cohen, 1963). However, the fact that words which can be similarly categorised also tend to be highly associated makes it difficult to measure the effects of either variable alone. Marshall (1967a, b), in an attempt to manipulate association level and category membership independently, measured the retention of lists comprising 12 pairs of words of low or medium levels of associativity. He found that recall was greater for those lists in which both words in a pair were from the same category. There was also a greater tendency for such word-pairs to be recalled together. These results appear to indicate that the categorisation variable affects recall independently of associativity. However, such a conclusion may not be justified.
66
W.A. Matthews, Association and categorisation effects on free recall
The associativity measures used by Marshall were the index of total association (ITA), and the mutual relatedness (MR) measures. As these measures are based upon both direct and indirect associations it follows that lists which score the same need not contain the same proportion of direct associations. Moreover, Marshall (1967b, exp. 3) has shown that direct associations facilitate recall and clustering better than indirect associations. It is clear, therefore, that simply equating lists on the ITA and MR measures does not provide an unambiguous test of categorisation effects. For example, were categorised lists to contain more direct associations than non-categorised lists, then this fact would explain their superior recall, making an explanation in terms of categorical facilitation unnecessary. A truly satisfactory attempt to assess the independent effects of associativity and categorisation requires that the lists are not only matched on the ITA or MR measure, but that equal associativity scores are based upon equal proportions of direct associations. In view of the scaling problemsoutlined above and theextremedifficulty of solving it, it may be premature to attempt to distinguish between organisational processes which depend upon the identification of category membership and those which are based on the associative relationships between the items, and in this experiment no attempt to do so is made. However, introducing identity of category membership among the associates to a stimulus may well produce distinguishable effects on the efficiency of list recall, the clustering patterns which occur and the types of errors which are found, which are more easily explained by reference to the effects of category membership than to the increases in the mean association level of the associated set which the imposition of category homogeneity implies. This experiment is intended to explore such differences. Using normative material derived from continued rather than single association norms (Matthews, 1969), the retention of 18 word lists was measured in 2 X 2 X 2 factorial design in which each of 2 levels of association strength, categorical membership and word frequency were manipulated. Association strength between the eliciting stimulus and the 2 associates to it (which make up the 3-word group from which the 18 word lists were constructed) was set at a high or low level. (Control lists of zero association strength were also used.) Categorical membership was manipulated by selecting the 2 associates from either a single semantic category or from 2 clearly separable semantic categories. Thus
W.A. Matthews, Associntion and categorisation effects on free recall
67
in the high association condition, this led to an increase in the mean level of association in the categorised lists when compared to the noncategorised lists because of the inter-word associations between the two similarly categorised associates, and also to a different pattern of association within each 3-word group, with associative connections being equally present between the 3 words, rather than from the stimulus to each associate. In the low association condition, the categorised lists had a mean association level (based on a subsequent rating task) approximating to that of non-categorised high association lists, (see table 2) but having a different pattern of association; this association level was obviously higher than that of low association non-categorised lists and had a different pattern. Strength (level of association) and pattern (category membership) are separately referred to throughout the subsequent report. Word frequency (as measured on the Thorndike-Lorge word count) was also varied using high and low levels. The aims of the experiment were: (a) to evaluate the effects of association level and word frequency on the recall of categorised and non-categorised word lists; (b) to investigate the clustering patterns found in recall for the different types of list; (c) to specify the error patterns obtained in the recall of the different types of list.
Experiment Material Eighteen-word lists were constructed which were organ&d into 6 sets of 3 associated words. Three variables were manipulated and a description of these follows: (1) associativity; two levels of association high (HA) (given by between 7-40 individuals) and loti (LA) (given by 1, 2 or 3 individuals from the norm-producing group of 50 students). The norms were produced by a continued association method but the responses were not chained (Matthews, 1969). (2) Two levels of word frequency; HF (AA or A words on the Thorndike-Lorge G count) and LF (words occurring less than 50 times per million words sampled (Thorndike and Lorge, 1944). (3) The 3-word groups either categorised or non-categorised. In the former condition, the two associates were members of the same semantic category (e.g. cabin (S) - ship (Rr) boat (Rs); in the latter they were categorically unrelated (e.g. van (S) - driver (R 1) gears (Ra). (Control lists were also produced which consisted of 18 unassociated words of high or low frequency.)
68
WA. Matthews, Association and categorisation effects on free recall
Des&n Two sets of 20 lists (sets A and B) were produced in this way which were identical in terms of the formal manipulated variables but differed in the words used. Each set (A and B) could then be divided in 2 identical subsets of 10 lists (which again differed in the words used) in terms of the formal independent variables. Each subset of 10 lists contained 1 HF and 1 LF control list of unassociated words; the 8 remaining lists being 2 high association lists of high frequency words; 2 high associaton lists of low frequency words; 2 low association lists of high frequency words and 2 low association lists of low frequency words. One list of each pair consisted of categorised word sets and the other list of non-categorised word sets. Examples of the lists used appear in table 1. Procedure The experimental session consisted of a learning session followed by a brief rating task designed to obtain information on word relationships. Learning task. All lists were recorded in a male monotone on magnetic tape at a rate of 1 word/set. Each list was presented 3 times in succession with recall required after each presentation. Within each list, the order of the 6 blocks was constant over the 3 presentations, but this order was different in each of 10 randomisations. The 10 different random orders of the lists in each set (set A or set B) were produced with the constraint that each type of list was sampled once in the first 10 trials. Each of the 10 randomisations was learned by 2 subjects so that 20 subjects learned set A and 20 subjects learned set B. Recall was unpaced and written on response drums which the subject moved on after a response had been written so that he did not see his previous responses. There were 2 practice lists and in order to reduce the effects of fatigue and boredom, there were 3 short breaks during the 2-hr experimental session. Subjects were run in pairs. This immediately followed the learning session. Forty halfmatrices were conRating task. structed from the 40-word lists used in the learning session, the only difference being that in the matrices, associatively related words did not appear together. Four sets of 10 such matrices were constructed, each containing 1 example of each list type. Each subject was presented with one of the sets and asked to make all pair-wise comparisons, marking with a tick each pair of words judged to be related in any way. Except for the control lists, no subjects rated matrices based on lists which he had learned. Emphasis was placed on a rapid response. The order of matrix presentation was randomised across subjects. These data are summarised in table 2. Their relevance to the recall data is discussed later.
Results the mean number of items correctly recalled in each condition is pres(1) Recall data: ented in table 3. Omitting control lists, the recall scores were subjected to an analysis of variance for 4 repeated treatments (associativity, word frequency, categorisation and trials), and 1 nonrepeated treatment (sets A and B) (Kirk, 1968). As the word set treatment was not a significant source of variability (F< l), it will not be discussed further. The 4 main treatment effects were all significant (for associativity, F(1,38) = 178.56, p< 0.001; for categorisation, F(1,38) = 43.10, p< 0.001; for word frequency, F(!,38) = 90.11, p< 0.001; for trials, F(2.76) = 1187.52, p< O.tiOl). The significant trials effect indicates that performance improved consistently over trials but as there are no significant interactions will not be discussed further. The interaction of word frequency with categorisation was significant (F(1.38) = 5.92, p< 0.02) as was that between association level and word frequency (F(1,38) = 4.67, p< 0.05). The interaction of association X word frequency X categorisation was also significant (F( 1,38) = 5.17, p< 0.05). The significant 3-way interaction suggests that the 2-way significant interactions should be considered separately at each level of the third factor and a detailed analysis along these lines follows.
W.A. Matthews, Association and categorization effects on free recall
69
262 201
217.5 (33)
Bl B2
Mean
(28)
117
A2
13.05 13.14
13.11
A B
Overall mean
HAHF
(77) (69)
(.54)
(.45)
213.0 (.61)
176
182
236
258
HALF a b
12.75
12.68 12.80
HALF
Non-categorised
(.32) (39)
(32)
290
Al
HAHF b a
Non categorised lists
(34) (34)
(.26)
(.24)
b
10.95
10.41 11.48
LAHF
(.49) (58) (71)
(31)
177.5 (.52)
152 100
281
177
LALF a b (.45) (.55) (72)
(.52)
274.75(.56)
304 170
282
343
HAHF a b
(78) (.61)
(.61)
(.64)
207.25(.66)
199 213
226
191
HALF a b
Categorised lists
10.33
9.61 11.04
LALF
13.69
12.95 14.44
HAHF
Categorised
12.90
12.90 12.90
HALF
(46) (.47)
(.33)
(.33)
231.75(.40)
262 133
311
221
LAHF a b
12.28
12.57 11.99
LAHF
Table 3 Mean number of words correct collapsed over 3 trials.
184.25(.30)
199 90
273
175
a
LAHF
(.66) (-56) (53)
(.42)
11.26
11.57 10.95
LALF
210.5 (54)
222 173
267
180
LALF a b
(.Ll)
(.Ll)
b
9.56
9.40 9.73
HF
Controls
155.5 (.ll)
276
346
HF a
Control
(13)
(09)
b
7.89
7.69 8.09
HF
119.5 (11)
247
231
LF a
Table 2 (a) Total number of instances of related words and (b) related words from within a presented cluster as a proportion of the total number of words judged to be related, shown separately for each example of each condition but summed over 10 subjects (20 subjects for control lists).
W.A. Matthews, Association and categorisation effects on free recall
71
A test of simple main effects, (Kirk, 1968) showed that significant facilitation occurred in the recall of the categorised over the non-categorised lists in the LAHF (F(1,76) = 51.8, p< 0.01) and LALF (F(1,76) = 10.74, p< 0.05) conditions. Facilitation also occurred with categorised HAHF lists (F(1,76) = 6.8, p< 0.05), but not with HALF lists. The greater facilitation of LA lists is unlikely to be due to ceiling effects. Only 56 from 160 scores were at their maximum on trial 3 in the HA categorised condition compared with 46 from 160 in the HA non-categorised condition. The limited effects of either increased association level or improved categorisation opportunity with highly associated lists repeats the result reported by Marshall (1967). High association produced significant recall facilitation at each of the 4 points on the categorised/non-categorised x word frequency (HF, LF) dimension (HF categorised, F(1,67) = 20.6 p< 0.01; HF non-categorised, F(1,76) = 79.4, p< 0.01; LF categorised, F(1,76 = 61.3, p< 0.01; and LF non-categorised, F(1.76) = 96.7, p< 0.01). The amount of facilitation was greater in the non-categorised condition with both HF and LF lists. The effect of word frequency was less consistent. HF lists were significantly better recalled than LF lists in the HA categorised condition (F(1,76) = 10.65, p< 0.01). The amount of facilitation was greater in the non-categorised condition with both HF and LF lists. The effect of word frequency was less consistent. HF lists were significantly better recalled than LF lists in the HA categorised condition (F(1,76) = 10.65, p< 0.05) but not in the HA non-categorised condition. High frequency produced significant facilitation in both LA categorised and non-categorised conditions (F(1,76) = 78.75; 14.80, bothp< 0.01). (2) Clustering data: from each subject’s response protocols, the number of words reported in a sequence which matched the associative organisation built into the lists was extracted. This measure is based upon the incidence of pairs of such related words reported by each subject adjusted by an estimate of the amount of such clustering which may have occurred by chance (Bousfield and Bousfield, 1966). The estimate for the control lists was obtained using position as a basis. These measures of clustering are shown in table 4. The scores (excluding the control lists) were submitted to a repeated measures analysis of variance which is not reported in detail. The main factors of trials, association level, word frequency and categorisation, each produced significant variability (respectively F(2,76) = 529.48, p< 0.001; F(1,38) = 126.38, p< 0.001; F(1,38) = 24.10, p< 0.001; and F(1,38) = 23.89, p< 0.001). Clustering increased over trials and with degree of categorisation, associativity and word frequency. The difference scores between categorised and non-categorised -conditions are also shown in table 4. These are obviously related to the recall score differences shown in table 3, suggesting that the basis of facilitation in the categorised condition lies in the clustering performance of the subjects. Table 4 Repetition scores by condition (mean of 3 trials and 40 subjects).
Non-catogerised Categorised Difference (categorized-) (non-categorised)
HAHF
HALF
6.28 6.81 +.5 3
6.23 6.41 +.18
LAHF
4.89 5.90 +1.01
LALF
Control HF
Control HF
4.50 5.12 +.62
3.89
2.89
12
W.A. Matthews, Association and categorisation effects on free recall
There is a problem using scores based on pairwise dependencies when applied to this experiment as the ease of recall of 3-word blocks cannot be directly identified and may vary in the different conditions. As this is potentially interesting information these data are reported separately in table 5. On trial 1, HA non-categorised lists produced little more organisation into 3-word groups than LA non-categorised lists but showed a more rapid improvement over trials. The HA categorised lists showed a higher level of initial clustering than other conditions and maintained this superiority. This may reflect the greater mean associative strength of the HA categorised lists when compared with any other condition. It could alternatively be due to the greater likelihood of a simple ‘coding’ response being relevant and easily produced so facilitating organisation and recalL The LA categorised lists did not differ from the HA non-categorised lists, but were clearly worse on the repetition measure (table 4) which considers pair dependency only and which is likely to be increased by direct associations between word pairs. The high values for the control lists reflect the finding that the recall of complete 3-word groups mainly occurred from the words presented at the beginning and end of the lists and show the importance of primary organisational processes with non-associated words. A final analysis of the clustering data was designed to show the order of recall of the words within each triplet. More specifically the frequency with which a recalled triplet began with the first presented word was expressed as a proportion of the total number of triplets recalled. These data are summarised in table 6. Because of the large inter-subject variability in clustering performance, comparisons were restricted to those between the same subject groups. There is no instance in which a categorised condition produced a lower score than a non-categorised condition. This supports the view that in categoriscd lists, the first word of a group acts as a coding and probably a retrieval cue. these data were classified as either associative or repetitions, or other (3) Error data: errors. They are shown in table 7. Table 5 Total numbers of triplets recalled by condition and trial for the 4 different examples of each list combination expressed as a proportion of total recall (40 subjects).
LALF
Categoriscd lists HAHF HALF
LAHF
LALF
Control -HF LF
.41 59 .67 ..58
.I0 .79 .92 .80
.65 .67 .83 .I2
Sl .68 .I4 .66
.32 .33 .36 .34
Non-categorised lists HAHF HALF LAHF Tl T2 T3 Mean
.58 .I9 .85 .74
.53 .69 .80 .67
.50 .60 ..59 .56
.65 .78 .88 .I1
.32 .26 .26 .28
Table 6 Proportion of recalled triplets which begin with the first presented word of the group summed over 3 trials by condition.
A(S l-20) B(S21-40)
Non-categorised lists HAHF HALF LAHF
LALF
Categorised lists HAHF HALF
LAHF
LALF
Controls HF LF
.71 .74
.67 .81
.85 .83
.86 .85
.75 .87
.81 .70 .83 .81
.1-l .68
.76 .83
.83 .72
W.A. Matthews, Association and categorisation effects on free recall
73
14
W.A. Matthews, Association and categorisation effects on free recall
(a) Errors were defined as associative when the incorrect items were clearly related to members of the presented 3-word groups. Identification of the associative errors was carried out by the experimenter who also specified the word to which the error was judged to be associated. 498 such pairs were initially extracted. Duplicated pairs were omitted and the remainder were randomly arranged among 30 HA and 30 LA pairs derived from the norms mentioned earlier. Five subjects (who had not participated in the learning task) rated these pairs on a 7 point scale (ranging from 7 highly associated to 1 not associated). Six error pairs in which the mean rated value did not exceed that of the LA pairs were discarded. The mean rated value for the three sets of pairs were, HA control 5.16, LA control 3.38, and error pairs 4.76; (b) repetitions of items previously correctly or incorrectly reported; (c) other errors (including acoustic errors). A number of interesting points arise (which are not affected by the use of error data in its raw form or as deviations from chance values as estimated by control list performance). The proportion of associative errors is greater in categorised lists than in comparable noncategorised lists, while the control lists contain very few such errors. Repetitions, on the other hand, occur least frequently in categorised lists. ‘Other’ errors decrease in frequency as the lists change from control through low association to high association. One further measure was extracted. This was the distance between (1) the nearest related word to an associative error, and (2) a repetition error and the nearest earlier occurrence of that item in the recalled list. The distance between adjacent items was given a value of 1. This measure was not applicable to ‘other’ errors. The mean distance over 3 trials for the associative error category was 1.30 (range 1.19 to 11.54)and did not differ between list types. Clearly if associative errors occur, they appear very close to the associatively similar items. Analysis of the repetition data is made more clear by considering the three types of list separately. The mean distance for the three types of list was: categorized lists, 8.33 (range 8.05-8.93); non-categorised lists, 7.19 (range 6.26-7.76) and control lists, 5.70 (range 5.026.38). The mean distance between repetitions is obviously greater than that between associative errors and their related words, and consistently increases from control lists through noncategorised to categorised lists.
Discussion Association theorists claim that words become associated to each other at varying strengths through the effects of the individuals experience; that the basis of these connections is contiguity in space and time which as frequency of occurrence increases produces increments to the strength of associations. Recall following learning is assumed to increase with the frequency of such contiguous occurrences. Obviously, a word may have associative connections of varying strength to more than a single word. Associations between the words produces the sequential recall patterns often found. Category coding is a less mechanistic approach in which the subject using cognitive processes is assumed to extract the main semantic content of the presented items (again presumably based on the effects of
W.A. Matthews, Association and categorisation effects on free recall
15
past experience). This material is stored for later recall in a system with at least two levels of organisation, one of the individual items; the other of summarising codes. That category coding needs to be postulated in all memory situations using semantically related words has been doubted by Gofer ( 1966), who believed that associative relationships were adequate to summark a range of experimental results which apparently required a category coding notion (e.g. Cohen, 1963). However, the value of applying associative concepts to other results (e.g. Marshall, 1967a) was doubted. In this experiment, non-categorised lists show similar recall levels at HA and LA points, to those obtained in earlier experiments (e.g. Matthews and Manasse, 1970) and could be ascribed to increases in the frequency and strength of associative connections. The effect of introducing category membership as a manipulated factor was to further improve the efficiency of recall. This effect was greater with HF words than LF words and LA lists than HA lists. The variation between HF and LF lists might be due to categorisation producing a greater reduction in the more varied inter-item associative connections between HF words (cf. Underwood and Schulz, 1960) which in uncategorised conditions may limit coding or retrieval efficiency. The smaller increase in HA than LA lists may be due to the fact that the facilitative effects of increasing associative level on recall are generally not linear but of a negative accelerated form (see Matthews, 1966). Thus the possibility of category coding is present in this data but cannot be clearly demonstrated because of the presence of additional or stronger direct associations between the words in the categorised lists. However, in trying to understand the processes involved in producing the recall data, the rating scores in table 2 are relevant. For non-categorised lists, recall increased with the total number of words in the list judged to be related, (mean scores, table 2 measure a). Using measure b from table 2, i.e. mean number of the words within each of the 6 presented clusters that are judged to be related, expressed as a proportion of the total number of words in the list judged to be related (a measure indicating within-group cohesiveness) this trend is absent. With the single exception of the HALF condition, this pattern of results occurs in the categorised lists condition. Thus with both types of list, the total matrix of associative connections predicts recall performance better than the within-category cohesiveness measure, and could be used as evidence in favour of the importance of direct associations in the production of recall.
76
W.A. Matthews, Association and categorisation effects on free recall
However, the fact that the first-presented word in a group was recalled first more frequently in the categorised list condition than in the non-categorised list condition would not have been predicted by an associative model. Such a model would simply predict that the effects of categorisation would be to increase overall recall and clustering. This increased incidence of recall of the eliciting stimulus in the initial position suggests that some ‘coding’ process, by which the characteristics of the items in the presented group can be summarised by the eliciting stimulus, is involved in storage or retrieval. The error data support this interpretation. The greater proportion of associative errors plus the reduced incidence of repetitions in the categorised list condition suggest the use of some coding label, which leads to the production of semantically similar ‘false positives’ in recall. In summary, increases in associative strength within a list facilitate recall. This occurs whether the increases are between an eliciting stimulus and its direct associates or between all the three words in the group. However, in the latter case, the pattern of recall as measured by clustering and errors differs from that found in the former case. More clustering into 3-word groups, a higher incidence of initial recall of the first presented word of the 3-word group and an increased incidence of associative errors takes place. This indicates that different types of processing occur and that these are determined by the pattern of association in the presented list and not only by the mean association level of these lists, supporting Cofer’s ( 1966) view that both processes, direct associative effects and category coding may occur. As in this experiment, all subjects experienced both types of list, this result suggests that these are subjective strategies largely controlled by the perceived characteristics of the list.
References Bousfield, W.A., 1953. The occurrence of clustering in the recall of randomly arranged associates. Journal of General Psychology 49,229-240. Bousfield, A.K. and W.A. Bousfield, 1966. Measurement of clustering and of sequential constancies in repeated free recall. Psychological Reports 19,935-942. Cofer, C.N., 1966. Some evidence for coding processes derived from clustering in free recall. Journal of Verbal Learning and Verbal Behaviour 5, 188- 192. Cohen, B.H., 1963. Recall of categorised word lists. Journal of Experimental Psychology 65, 368-376. Deese, J., 1959. Influence of inter-item associative strength upon immediate free recall. Psychological Reports 5, 305-312.
W.A. Matthews, Association and categorisation effects on free recall
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Kirk, R.E., 1968. Experimental design procedures for the behavioural sciences. Belmont California: Wadsworth. Marshall, G.R., 1967a. Effect of total association and conceptual cohesiveness among words on recall clustering and recognition association. Psychological Reports 20, 39-44. Marshall, G.R., 1967b. Stimulus characteristics contributing to organisation in free recall. Journal of Verbal Learning and Verbal Behaviour 6, 364-374. Matthews, W.A., 1966. Continued word associations and free recall. Quarterly Journal of Experimental Psychology 17,31-38. Matthews, W.A., 1969. Norms from continued word associations. Bulletin of the British Psychological Society 22, 193-195. Matthews, W.A. and K. Manasse, 1970. Associative factors in free recall. Quarterly Journal of Experimental Psychology 22, 177-184. Thorndike, E.L. and I. Lorge, 1944. The teachers word book of 30,000 words. New York: Teachers College, Columbia University. Tulving, E., 1968. Theoretical issues in free recall. In: T.R. Dixon and D.L. Horton (eds.), Verbal behaviour and general behaviour theory. Englewood Cliffs, N.J.: Prentice-Hail.
37 (1973)
ASSOCIATION
65-77.
0 North-Holland
Publishing
AND CATEGORISATION FREE RECALL
Company
EFFECTS ON
W.A.MATTHEWS Department
of Psychology,
Accepted
University of Southampton,
November
U.K.
1, 1972
Lists of 18 words which varied in mean associative strength, the category membership of the associations and in word frequency were presented to subjects 3 times with recall required after each presentation. Recall efficiency increased with association level and with similarly categorised associates. In lists of high mean associative strength which consisted of similarly categorised words, the recall of high frequency word lists was facilitated but at low levels of associative strength, with similarly categorised words, recall was facilitated at both levels of word frequency used. Clustering and errors which were associatively related to the items being learned were greater in lists which contained sets of similarly categorised associates.
It has been reliably demonstrated that the free recall of word lists increases with the strength of the associations between the individual words (e.g. Deese, 1959; Matthews, 1966). Facilitation of recall also increases when the words making up the list can be grouped into clearly defined categories (e.g. Bousfield, 1953; Cohen, 1963). However, the fact that words which can be similarly categorised also tend to be highly associated makes it difficult to measure the effects of either variable alone. Marshall (1967a, b), in an attempt to manipulate association level and category membership independently, measured the retention of lists comprising 12 pairs of words of low or medium levels of associativity. He found that recall was greater for those lists in which both words in a pair were from the same category. There was also a greater tendency for such word-pairs to be recalled together. These results appear to indicate that the categorisation variable affects recall independently of associativity. However, such a conclusion may not be justified.
66
W.A. Matthews, Association and categorisation effects on free recall
The associativity measures used by Marshall were the index of total association (ITA), and the mutual relatedness (MR) measures. As these measures are based upon both direct and indirect associations it follows that lists which score the same need not contain the same proportion of direct associations. Moreover, Marshall (1967b, exp. 3) has shown that direct associations facilitate recall and clustering better than indirect associations. It is clear, therefore, that simply equating lists on the ITA and MR measures does not provide an unambiguous test of categorisation effects. For example, were categorised lists to contain more direct associations than non-categorised lists, then this fact would explain their superior recall, making an explanation in terms of categorical facilitation unnecessary. A truly satisfactory attempt to assess the independent effects of associativity and categorisation requires that the lists are not only matched on the ITA or MR measure, but that equal associativity scores are based upon equal proportions of direct associations. In view of the scaling problemsoutlined above and theextremedifficulty of solving it, it may be premature to attempt to distinguish between organisational processes which depend upon the identification of category membership and those which are based on the associative relationships between the items, and in this experiment no attempt to do so is made. However, introducing identity of category membership among the associates to a stimulus may well produce distinguishable effects on the efficiency of list recall, the clustering patterns which occur and the types of errors which are found, which are more easily explained by reference to the effects of category membership than to the increases in the mean association level of the associated set which the imposition of category homogeneity implies. This experiment is intended to explore such differences. Using normative material derived from continued rather than single association norms (Matthews, 1969), the retention of 18 word lists was measured in 2 X 2 X 2 factorial design in which each of 2 levels of association strength, categorical membership and word frequency were manipulated. Association strength between the eliciting stimulus and the 2 associates to it (which make up the 3-word group from which the 18 word lists were constructed) was set at a high or low level. (Control lists of zero association strength were also used.) Categorical membership was manipulated by selecting the 2 associates from either a single semantic category or from 2 clearly separable semantic categories. Thus
W.A. Matthews, Associntion and categorisation effects on free recall
67
in the high association condition, this led to an increase in the mean level of association in the categorised lists when compared to the noncategorised lists because of the inter-word associations between the two similarly categorised associates, and also to a different pattern of association within each 3-word group, with associative connections being equally present between the 3 words, rather than from the stimulus to each associate. In the low association condition, the categorised lists had a mean association level (based on a subsequent rating task) approximating to that of non-categorised high association lists, (see table 2) but having a different pattern of association; this association level was obviously higher than that of low association non-categorised lists and had a different pattern. Strength (level of association) and pattern (category membership) are separately referred to throughout the subsequent report. Word frequency (as measured on the Thorndike-Lorge word count) was also varied using high and low levels. The aims of the experiment were: (a) to evaluate the effects of association level and word frequency on the recall of categorised and non-categorised word lists; (b) to investigate the clustering patterns found in recall for the different types of list; (c) to specify the error patterns obtained in the recall of the different types of list.
Experiment Material Eighteen-word lists were constructed which were organ&d into 6 sets of 3 associated words. Three variables were manipulated and a description of these follows: (1) associativity; two levels of association high (HA) (given by between 7-40 individuals) and loti (LA) (given by 1, 2 or 3 individuals from the norm-producing group of 50 students). The norms were produced by a continued association method but the responses were not chained (Matthews, 1969). (2) Two levels of word frequency; HF (AA or A words on the Thorndike-Lorge G count) and LF (words occurring less than 50 times per million words sampled (Thorndike and Lorge, 1944). (3) The 3-word groups either categorised or non-categorised. In the former condition, the two associates were members of the same semantic category (e.g. cabin (S) - ship (Rr) boat (Rs); in the latter they were categorically unrelated (e.g. van (S) - driver (R 1) gears (Ra). (Control lists were also produced which consisted of 18 unassociated words of high or low frequency.)
68
WA. Matthews, Association and categorisation effects on free recall
Des&n Two sets of 20 lists (sets A and B) were produced in this way which were identical in terms of the formal manipulated variables but differed in the words used. Each set (A and B) could then be divided in 2 identical subsets of 10 lists (which again differed in the words used) in terms of the formal independent variables. Each subset of 10 lists contained 1 HF and 1 LF control list of unassociated words; the 8 remaining lists being 2 high association lists of high frequency words; 2 high associaton lists of low frequency words; 2 low association lists of high frequency words and 2 low association lists of low frequency words. One list of each pair consisted of categorised word sets and the other list of non-categorised word sets. Examples of the lists used appear in table 1. Procedure The experimental session consisted of a learning session followed by a brief rating task designed to obtain information on word relationships. Learning task. All lists were recorded in a male monotone on magnetic tape at a rate of 1 word/set. Each list was presented 3 times in succession with recall required after each presentation. Within each list, the order of the 6 blocks was constant over the 3 presentations, but this order was different in each of 10 randomisations. The 10 different random orders of the lists in each set (set A or set B) were produced with the constraint that each type of list was sampled once in the first 10 trials. Each of the 10 randomisations was learned by 2 subjects so that 20 subjects learned set A and 20 subjects learned set B. Recall was unpaced and written on response drums which the subject moved on after a response had been written so that he did not see his previous responses. There were 2 practice lists and in order to reduce the effects of fatigue and boredom, there were 3 short breaks during the 2-hr experimental session. Subjects were run in pairs. This immediately followed the learning session. Forty halfmatrices were conRating task. structed from the 40-word lists used in the learning session, the only difference being that in the matrices, associatively related words did not appear together. Four sets of 10 such matrices were constructed, each containing 1 example of each list type. Each subject was presented with one of the sets and asked to make all pair-wise comparisons, marking with a tick each pair of words judged to be related in any way. Except for the control lists, no subjects rated matrices based on lists which he had learned. Emphasis was placed on a rapid response. The order of matrix presentation was randomised across subjects. These data are summarised in table 2. Their relevance to the recall data is discussed later.
Results the mean number of items correctly recalled in each condition is pres(1) Recall data: ented in table 3. Omitting control lists, the recall scores were subjected to an analysis of variance for 4 repeated treatments (associativity, word frequency, categorisation and trials), and 1 nonrepeated treatment (sets A and B) (Kirk, 1968). As the word set treatment was not a significant source of variability (F< l), it will not be discussed further. The 4 main treatment effects were all significant (for associativity, F(1,38) = 178.56, p< 0.001; for categorisation, F(1,38) = 43.10, p< 0.001; for word frequency, F(!,38) = 90.11, p< 0.001; for trials, F(2.76) = 1187.52, p< O.tiOl). The significant trials effect indicates that performance improved consistently over trials but as there are no significant interactions will not be discussed further. The interaction of word frequency with categorisation was significant (F(1.38) = 5.92, p< 0.02) as was that between association level and word frequency (F(1,38) = 4.67, p< 0.05). The interaction of association X word frequency X categorisation was also significant (F( 1,38) = 5.17, p< 0.05). The significant 3-way interaction suggests that the 2-way significant interactions should be considered separately at each level of the third factor and a detailed analysis along these lines follows.
W.A. Matthews, Association and categorization effects on free recall
69
262 201
217.5 (33)
Bl B2
Mean
(28)
117
A2
13.05 13.14
13.11
A B
Overall mean
HAHF
(77) (69)
(.54)
(.45)
213.0 (.61)
176
182
236
258
HALF a b
12.75
12.68 12.80
HALF
Non-categorised
(.32) (39)
(32)
290
Al
HAHF b a
Non categorised lists
(34) (34)
(.26)
(.24)
b
10.95
10.41 11.48
LAHF
(.49) (58) (71)
(31)
177.5 (.52)
152 100
281
177
LALF a b (.45) (.55) (72)
(.52)
274.75(.56)
304 170
282
343
HAHF a b
(78) (.61)
(.61)
(.64)
207.25(.66)
199 213
226
191
HALF a b
Categorised lists
10.33
9.61 11.04
LALF
13.69
12.95 14.44
HAHF
Categorised
12.90
12.90 12.90
HALF
(46) (.47)
(.33)
(.33)
231.75(.40)
262 133
311
221
LAHF a b
12.28
12.57 11.99
LAHF
Table 3 Mean number of words correct collapsed over 3 trials.
184.25(.30)
199 90
273
175
a
LAHF
(.66) (-56) (53)
(.42)
11.26
11.57 10.95
LALF
210.5 (54)
222 173
267
180
LALF a b
(.Ll)
(.Ll)
b
9.56
9.40 9.73
HF
Controls
155.5 (.ll)
276
346
HF a
Control
(13)
(09)
b
7.89
7.69 8.09
HF
119.5 (11)
247
231
LF a
Table 2 (a) Total number of instances of related words and (b) related words from within a presented cluster as a proportion of the total number of words judged to be related, shown separately for each example of each condition but summed over 10 subjects (20 subjects for control lists).
W.A. Matthews, Association and categorisation effects on free recall
71
A test of simple main effects, (Kirk, 1968) showed that significant facilitation occurred in the recall of the categorised over the non-categorised lists in the LAHF (F(1,76) = 51.8, p< 0.01) and LALF (F(1,76) = 10.74, p< 0.05) conditions. Facilitation also occurred with categorised HAHF lists (F(1,76) = 6.8, p< 0.05), but not with HALF lists. The greater facilitation of LA lists is unlikely to be due to ceiling effects. Only 56 from 160 scores were at their maximum on trial 3 in the HA categorised condition compared with 46 from 160 in the HA non-categorised condition. The limited effects of either increased association level or improved categorisation opportunity with highly associated lists repeats the result reported by Marshall (1967). High association produced significant recall facilitation at each of the 4 points on the categorised/non-categorised x word frequency (HF, LF) dimension (HF categorised, F(1,67) = 20.6 p< 0.01; HF non-categorised, F(1,76) = 79.4, p< 0.01; LF categorised, F(1,76 = 61.3, p< 0.01; and LF non-categorised, F(1.76) = 96.7, p< 0.01). The amount of facilitation was greater in the non-categorised condition with both HF and LF lists. The effect of word frequency was less consistent. HF lists were significantly better recalled than LF lists in the HA categorised condition (F(1,76) = 10.65, p< 0.01). The amount of facilitation was greater in the non-categorised condition with both HF and LF lists. The effect of word frequency was less consistent. HF lists were significantly better recalled than LF lists in the HA categorised condition (F(1,76) = 10.65, p< 0.05) but not in the HA non-categorised condition. High frequency produced significant facilitation in both LA categorised and non-categorised conditions (F(1,76) = 78.75; 14.80, bothp< 0.01). (2) Clustering data: from each subject’s response protocols, the number of words reported in a sequence which matched the associative organisation built into the lists was extracted. This measure is based upon the incidence of pairs of such related words reported by each subject adjusted by an estimate of the amount of such clustering which may have occurred by chance (Bousfield and Bousfield, 1966). The estimate for the control lists was obtained using position as a basis. These measures of clustering are shown in table 4. The scores (excluding the control lists) were submitted to a repeated measures analysis of variance which is not reported in detail. The main factors of trials, association level, word frequency and categorisation, each produced significant variability (respectively F(2,76) = 529.48, p< 0.001; F(1,38) = 126.38, p< 0.001; F(1,38) = 24.10, p< 0.001; and F(1,38) = 23.89, p< 0.001). Clustering increased over trials and with degree of categorisation, associativity and word frequency. The difference scores between categorised and non-categorised -conditions are also shown in table 4. These are obviously related to the recall score differences shown in table 3, suggesting that the basis of facilitation in the categorised condition lies in the clustering performance of the subjects. Table 4 Repetition scores by condition (mean of 3 trials and 40 subjects).
Non-catogerised Categorised Difference (categorized-) (non-categorised)
HAHF
HALF
6.28 6.81 +.5 3
6.23 6.41 +.18
LAHF
4.89 5.90 +1.01
LALF
Control HF
Control HF
4.50 5.12 +.62
3.89
2.89
12
W.A. Matthews, Association and categorisation effects on free recall
There is a problem using scores based on pairwise dependencies when applied to this experiment as the ease of recall of 3-word blocks cannot be directly identified and may vary in the different conditions. As this is potentially interesting information these data are reported separately in table 5. On trial 1, HA non-categorised lists produced little more organisation into 3-word groups than LA non-categorised lists but showed a more rapid improvement over trials. The HA categorised lists showed a higher level of initial clustering than other conditions and maintained this superiority. This may reflect the greater mean associative strength of the HA categorised lists when compared with any other condition. It could alternatively be due to the greater likelihood of a simple ‘coding’ response being relevant and easily produced so facilitating organisation and recalL The LA categorised lists did not differ from the HA non-categorised lists, but were clearly worse on the repetition measure (table 4) which considers pair dependency only and which is likely to be increased by direct associations between word pairs. The high values for the control lists reflect the finding that the recall of complete 3-word groups mainly occurred from the words presented at the beginning and end of the lists and show the importance of primary organisational processes with non-associated words. A final analysis of the clustering data was designed to show the order of recall of the words within each triplet. More specifically the frequency with which a recalled triplet began with the first presented word was expressed as a proportion of the total number of triplets recalled. These data are summarised in table 6. Because of the large inter-subject variability in clustering performance, comparisons were restricted to those between the same subject groups. There is no instance in which a categorised condition produced a lower score than a non-categorised condition. This supports the view that in categoriscd lists, the first word of a group acts as a coding and probably a retrieval cue. these data were classified as either associative or repetitions, or other (3) Error data: errors. They are shown in table 7. Table 5 Total numbers of triplets recalled by condition and trial for the 4 different examples of each list combination expressed as a proportion of total recall (40 subjects).
LALF
Categoriscd lists HAHF HALF
LAHF
LALF
Control -HF LF
.41 59 .67 ..58
.I0 .79 .92 .80
.65 .67 .83 .I2
Sl .68 .I4 .66
.32 .33 .36 .34
Non-categorised lists HAHF HALF LAHF Tl T2 T3 Mean
.58 .I9 .85 .74
.53 .69 .80 .67
.50 .60 ..59 .56
.65 .78 .88 .I1
.32 .26 .26 .28
Table 6 Proportion of recalled triplets which begin with the first presented word of the group summed over 3 trials by condition.
A(S l-20) B(S21-40)
Non-categorised lists HAHF HALF LAHF
LALF
Categorised lists HAHF HALF
LAHF
LALF
Controls HF LF
.71 .74
.67 .81
.85 .83
.86 .85
.75 .87
.81 .70 .83 .81
.1-l .68
.76 .83
.83 .72
W.A. Matthews, Association and categorisation effects on free recall
73
14
W.A. Matthews, Association and categorisation effects on free recall
(a) Errors were defined as associative when the incorrect items were clearly related to members of the presented 3-word groups. Identification of the associative errors was carried out by the experimenter who also specified the word to which the error was judged to be associated. 498 such pairs were initially extracted. Duplicated pairs were omitted and the remainder were randomly arranged among 30 HA and 30 LA pairs derived from the norms mentioned earlier. Five subjects (who had not participated in the learning task) rated these pairs on a 7 point scale (ranging from 7 highly associated to 1 not associated). Six error pairs in which the mean rated value did not exceed that of the LA pairs were discarded. The mean rated value for the three sets of pairs were, HA control 5.16, LA control 3.38, and error pairs 4.76; (b) repetitions of items previously correctly or incorrectly reported; (c) other errors (including acoustic errors). A number of interesting points arise (which are not affected by the use of error data in its raw form or as deviations from chance values as estimated by control list performance). The proportion of associative errors is greater in categorised lists than in comparable noncategorised lists, while the control lists contain very few such errors. Repetitions, on the other hand, occur least frequently in categorised lists. ‘Other’ errors decrease in frequency as the lists change from control through low association to high association. One further measure was extracted. This was the distance between (1) the nearest related word to an associative error, and (2) a repetition error and the nearest earlier occurrence of that item in the recalled list. The distance between adjacent items was given a value of 1. This measure was not applicable to ‘other’ errors. The mean distance over 3 trials for the associative error category was 1.30 (range 1.19 to 11.54)and did not differ between list types. Clearly if associative errors occur, they appear very close to the associatively similar items. Analysis of the repetition data is made more clear by considering the three types of list separately. The mean distance for the three types of list was: categorized lists, 8.33 (range 8.05-8.93); non-categorised lists, 7.19 (range 6.26-7.76) and control lists, 5.70 (range 5.026.38). The mean distance between repetitions is obviously greater than that between associative errors and their related words, and consistently increases from control lists through noncategorised to categorised lists.
Discussion Association theorists claim that words become associated to each other at varying strengths through the effects of the individuals experience; that the basis of these connections is contiguity in space and time which as frequency of occurrence increases produces increments to the strength of associations. Recall following learning is assumed to increase with the frequency of such contiguous occurrences. Obviously, a word may have associative connections of varying strength to more than a single word. Associations between the words produces the sequential recall patterns often found. Category coding is a less mechanistic approach in which the subject using cognitive processes is assumed to extract the main semantic content of the presented items (again presumably based on the effects of
W.A. Matthews, Association and categorisation effects on free recall
15
past experience). This material is stored for later recall in a system with at least two levels of organisation, one of the individual items; the other of summarising codes. That category coding needs to be postulated in all memory situations using semantically related words has been doubted by Gofer ( 1966), who believed that associative relationships were adequate to summark a range of experimental results which apparently required a category coding notion (e.g. Cohen, 1963). However, the value of applying associative concepts to other results (e.g. Marshall, 1967a) was doubted. In this experiment, non-categorised lists show similar recall levels at HA and LA points, to those obtained in earlier experiments (e.g. Matthews and Manasse, 1970) and could be ascribed to increases in the frequency and strength of associative connections. The effect of introducing category membership as a manipulated factor was to further improve the efficiency of recall. This effect was greater with HF words than LF words and LA lists than HA lists. The variation between HF and LF lists might be due to categorisation producing a greater reduction in the more varied inter-item associative connections between HF words (cf. Underwood and Schulz, 1960) which in uncategorised conditions may limit coding or retrieval efficiency. The smaller increase in HA than LA lists may be due to the fact that the facilitative effects of increasing associative level on recall are generally not linear but of a negative accelerated form (see Matthews, 1966). Thus the possibility of category coding is present in this data but cannot be clearly demonstrated because of the presence of additional or stronger direct associations between the words in the categorised lists. However, in trying to understand the processes involved in producing the recall data, the rating scores in table 2 are relevant. For non-categorised lists, recall increased with the total number of words in the list judged to be related, (mean scores, table 2 measure a). Using measure b from table 2, i.e. mean number of the words within each of the 6 presented clusters that are judged to be related, expressed as a proportion of the total number of words in the list judged to be related (a measure indicating within-group cohesiveness) this trend is absent. With the single exception of the HALF condition, this pattern of results occurs in the categorised lists condition. Thus with both types of list, the total matrix of associative connections predicts recall performance better than the within-category cohesiveness measure, and could be used as evidence in favour of the importance of direct associations in the production of recall.
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W.A. Matthews, Association and categorisation effects on free recall
However, the fact that the first-presented word in a group was recalled first more frequently in the categorised list condition than in the non-categorised list condition would not have been predicted by an associative model. Such a model would simply predict that the effects of categorisation would be to increase overall recall and clustering. This increased incidence of recall of the eliciting stimulus in the initial position suggests that some ‘coding’ process, by which the characteristics of the items in the presented group can be summarised by the eliciting stimulus, is involved in storage or retrieval. The error data support this interpretation. The greater proportion of associative errors plus the reduced incidence of repetitions in the categorised list condition suggest the use of some coding label, which leads to the production of semantically similar ‘false positives’ in recall. In summary, increases in associative strength within a list facilitate recall. This occurs whether the increases are between an eliciting stimulus and its direct associates or between all the three words in the group. However, in the latter case, the pattern of recall as measured by clustering and errors differs from that found in the former case. More clustering into 3-word groups, a higher incidence of initial recall of the first presented word of the 3-word group and an increased incidence of associative errors takes place. This indicates that different types of processing occur and that these are determined by the pattern of association in the presented list and not only by the mean association level of these lists, supporting Cofer’s ( 1966) view that both processes, direct associative effects and category coding may occur. As in this experiment, all subjects experienced both types of list, this result suggests that these are subjective strategies largely controlled by the perceived characteristics of the list.
References Bousfield, W.A., 1953. The occurrence of clustering in the recall of randomly arranged associates. Journal of General Psychology 49,229-240. Bousfield, A.K. and W.A. Bousfield, 1966. Measurement of clustering and of sequential constancies in repeated free recall. Psychological Reports 19,935-942. Cofer, C.N., 1966. Some evidence for coding processes derived from clustering in free recall. Journal of Verbal Learning and Verbal Behaviour 5, 188- 192. Cohen, B.H., 1963. Recall of categorised word lists. Journal of Experimental Psychology 65, 368-376. Deese, J., 1959. Influence of inter-item associative strength upon immediate free recall. Psychological Reports 5, 305-312.
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Kirk, R.E., 1968. Experimental design procedures for the behavioural sciences. Belmont California: Wadsworth. Marshall, G.R., 1967a. Effect of total association and conceptual cohesiveness among words on recall clustering and recognition association. Psychological Reports 20, 39-44. Marshall, G.R., 1967b. Stimulus characteristics contributing to organisation in free recall. Journal of Verbal Learning and Verbal Behaviour 6, 364-374. Matthews, W.A., 1966. Continued word associations and free recall. Quarterly Journal of Experimental Psychology 17,31-38. Matthews, W.A., 1969. Norms from continued word associations. Bulletin of the British Psychological Society 22, 193-195. Matthews, W.A. and K. Manasse, 1970. Associative factors in free recall. Quarterly Journal of Experimental Psychology 22, 177-184. Thorndike, E.L. and I. Lorge, 1944. The teachers word book of 30,000 words. New York: Teachers College, Columbia University. Tulving, E., 1968. Theoretical issues in free recall. In: T.R. Dixon and D.L. Horton (eds.), Verbal behaviour and general behaviour theory. Englewood Cliffs, N.J.: Prentice-Hail.