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Transfer in free-recall learning of overlapping lists of nonsense words
~OURNAL OF VERBAL LEARNING AND VERBAL BEHAVIOR 6, 9 2 2 - - 9 2 7
(1967)
Transfer in Free-Recall Learning of Overlapping Lists of Nonsense Words 1 W. R. GARNER AND RICHARD L. DEGERMAN Johns Hopkins University, Baltimore, Maryland 21218 The Ss were required to learn a list of eight nonsense words which was a subset from a total set of 16, and then to learn another subset of eight which contained four words from the original list. Learning diflqculty was found to be determined almost entirely by whether the internal structure of the subset was simple or complex. No facilitation in learning the second subset was found. Interference occurred when both the first and second subsets had one simple contingency between two letter positions and both contingencies involved a letter position in common. It is concluded that facilitation will occur only when the total learning task involves a meaningful total set of words, with a structure of the subsets perceived as related to the structure of the total set. Garner (1962) has pointed out that freerecall learning involves learning the properties of sets or subsets of items. More specifically, Garner and Whitman (1965) argued that the free-recall process is concerned with three levels of stimulus sets: The total set is the set of stimuli generated by orthogonal combinations of all the variables which define the stimuli, and learning of a total set of nonsense words involves learning all the letters which can occur at each letter position. The actual set is a subset of the total set, and is the set presented for learning. When the actual set is smaller than the total set, a structure exists, within the subset, that consists of relations between the variables making up the stimuli. This internal structure may be simple, consisting of contingencies between various pairs of letter positions, or it may be complex, consisting of interactions involving three or 1 This research was supported in part by grant MHl1062 from the National Institute of Mental Health to Johns Hopkins University. The senior author is now at Yale University.
more letter positions. Whitman and Garner (1962, 1968) and Garner and Whitman (1965) have shown that subsets with simple structure are much easier to learn than subsets with complex structure. The individual stimulus can be considered a third level of stimulus set, since each stimulus is also a subset of the total set. Whitman and Garner (1962, 1968), however, have shown that the rate at which a particular geometric pattern is learned is entirely a question of the properties of the larger subset of which it is a part, and has nothing to do with any unique properties of the individual stimulus. This conclusion is further strengthened by the finding of Garner and Whitman (1965) that learning of a total set of words prior to learning of a subset does not facilitate learning of the subset. In this latter study, which involved transfer as well as original learning, facilitation on the second task occurred only when the original learning was of a subset of eight from the total set of 16 words, when that subset had a simple form of
922
TRANSFER WITH OVERLAPPING LISTS structure, a n d w h e n the second l e a r n i n g i n v o l v e d either the c o m p l e m e n t of t h e o r i g i n a l subset or the total set itself. T h u s facilitation o c c u r r e d only w h e n the second set of words was the same size as the first, or i n c l u d e d the first set. Moreover, i n b o t h of these cases l e a r n i n g of t h e total set was involved, either b y use of the total set for s e c o n d l e a r n i n g or b y use of the complem e n t of the first set for the second learni n g task. Purpose of Experiment. The p r e s e n t exp e r i m e n t was d e s i g n e d to explore this p r o b l e m f u r t h e r b y r e q u i r i n g free-recall l e a r n i n g of n o n s e n s e words in t h e transfer p a r a d i g m , b u t w i t h first a n d second sul~sets w h i c h are the s a m e size a n d i n c l u d e some of the same words. T h e t w o subsets to b e l e a r n e d consist of eight words, four of w h i c h are t h e same, so t h a t 12 words are l e a r n e d i n the t w o tasks. T h e subsets are selected from a total set of 16. T h u s l e a r n i n g of the total set is n o t required. METHOD
Words The total set of nonsense words was the same as that used by Garner and Whitman (1965) and consisted of the 16 words which can be formed from all combinations of each of two letters in each of four letter positions. The first letter could be B or P, the second R or L, the third A or O, and the fourth J or Z. The subsets to be learned always consisted of eight of these words, claosen to have different kinds of internal structure as indicated below.
General Procedure Each S was run individually in a room with the only other person present, seated across a table from him. Each word was printed on a card with block capital letters 32-mm high and was shown to S by E one word at a time, in random order, With exposure time per word of 5 see. During this time S read the letters aloud. Immediately after seeing the last word in a set, S was required to write the words down, in any order. He was allowed 60 sec to reproduce the words and was encouraged to guess. After each trial the words were presented again in a dif-
E,
923
ferent random order, and trials were continued until S reached criterion of a correct reproduction of the eight words two trials in succession. However, trials were terminated without complete learning after 15, and no S was continued for more than 1 hr total time. This latter restriction prevented completion in a few cases. All Ss were undergraduate students at Johns Hopkins from the Introductory Psychology course.
Experimental Conditions All conditions required S to learn eight words on first leaming, then eight on second learning, with four of the eight words being the same on both lists. Thus half of the second list consisted of words from the first list. The experimental variations concerned the form of the internal structure in each of the two lists, with either a simple structure involving a single pair contingency or a complex structure involving an interaction uncertainty. Simple-Simple (S-S). (a) The two lists of words were: BLAJ, BLAZ, BLOJ, BLOZ, PRAJ, PRAZ, PROJ, PROZ and BLAJ, BLOJ, BRAJ, BROJ, PLAZ, PLOZ, PRAZ, PROZ. The first list has a pair contingency between the first two letter positions, and the second list has a pair contingency between the first and the fourth letter positions. Ten Ss were used for this condition, half learning each list first. (b) The two lists were: BRAJ, BRAZ, BROJ, BROZ, PLAJ, PLAZ, PLOJ, PLOZ and BLAZ, BLOJ, BRAZ, BROJ, PLAZ, PLOJ, PRAZ, PROJ. The first list has a pair contingency between the first two letter positions, and the second list has a pair contingency between the last two letter positions. Ten Ss were used for this condition, half learning each list first. Simple-Complex (S-C). (a) The two lists of words were: BRAJ, BRAZ, BROJ, BROZ, PLAJ, PLAZ, PLOJ, PLOZ and BLAJ, BLOZ, BRAJ, BROZ, PLAZ, PLOJ, PRAZ, PROJ. The first list has a pair contingency between the first two letter positions and the second list has an interaction involving the first, third, and fourth letter positions. Ten Ss were run on this condition, with the list with simple structure learned first. (b) The first list of words was the same as for S-C (a) with a pair contingency between the first two letter positions. The second list was: BLAJ, BLOZ, BRAZ, BROJ, PLAZ, PLOJ, PRAJ, PROZ. This second list has an interaction involving all four letter positions. Ten Ss were run on this condition, with the list with simple structure learned first.
924
GARNER AND DEGERMAN
Statistical analyses showed no significant differences 2 between S-C (a) and S-C (b), so resuits are presented for these 20 Ss as a single group. Complex-Simple (C-S). (a) and (b) C-S (a) used the stone word lists as S-C (a), but in the reverse order, and C-S (b) used the same word lists as S-C (b), but in the reverse order. Ten Ss were used for each subcondition, but since again statistical analyses showed no significant differences between the two conditions, results are presented for these 20 Ss as a single group. Complex-Complex (C-C). The two lists were: BLAZ, BLOJ, BRAJ, BROZ, PLAZ, PLOJ, PRAJ, PROZ, and BLAJ, BLOZ, BRAJ, BROZ, PLAZ, PLOJ, PRAZ, PROJ. The first list has an interaction involving the last three letter positions, and the second list has an interaction involving the first, third, and fourth letter positions. Five Ss were run with the two lists in the indicated order and three Ss were run with the lists in the reverse order.
RESULTS
The results were analyzed with a variety of measures: total errors, trials to criterion, learning curves, and correct recalls during the first four learning trials. The various measures all lead to the same conclusions, but results are presented only in terms of correct recalls during the first four trials, with any trials after criterion counted as entirely correct. The use of this measure gives somewhat greater sensitivity in showing transfer effects, and that was the primary concern of the experiment. In addition, it avoids some of the statistical instability produced by skewed distributions for total errors or trials to criterion.
First Learning Table 1 shows the results for first learning. On first learning, the major effect is that the subsets of eight words with simple structure are much easier to learn than subsets with complex structure. W i t h simple ~All statements of statistical significance are based on analysis of variance, at 5% level of significance.
TABLE 1 PERCENTAGE OF WORDS CORRECTLY RECALLED IN FIRST FOUR LEARNING TRIALS
Learning order Condition
N
1
,S-S (a) S-S (b) S-C (a and b) C-S (a and b) C-C
10 10 ~0 ~0 8
83.8 85.9 90.9 58.8 64.1
65.0 86.1 57.0 83.6 55.5
structure, the percentages correct on first four trials ranged from about 84 to 91, while the two conditions starting with complex structure gave percentages of about 59 and 64. This result completely confirms that found previously by Garner and Whitman (1965). Altogether three different forms of complex structure were used, one with an interaction between all four letter positions, one with an interaction between the first, third, and fourth letter positions, and one with an interaction between the last three letter positions. With this last type of interaction (used for five Ss in the C-C condition) the percentage of correct recalls was approximately 75, and was significantly greater than for the other two complex structures. Within the simple forms of structure, three different pair contingencies were used, involving the first two, the last two, or the first and last letter positions. There were no statistically significant differences in difficulty of initial learning for these three types. Nevertheless, there were slight differences, with a contingency between the first two le~er positions being easier to learn. Even though this difference is not statistically significant, in conjunction with the easier learning of an interaction contingency involving the last three letter positions, it suggests that learning of any
925
TRANSFER W / T H OVERLAPPING LISTS
structure is easier if the structure involves adjacent letter positions.
Transfer Learning The results for the second learning task are also shown in Table 1. With the exception of the S-S (a) condition, there is no evidence for either facilitation or interference in the transfer task: the difficulty of learning the second list of words depends entirely on the structure involved in that list of words and not at all on the structure of t h e first list of words. There is substantial and significant negative transfer for the S-S (a) conditibn, with the second subset being almost as difficult to learn as the subsets with complex structure. This condition is one in which a pair contingency between the first two letter positions exists on one list and a pair contingency between the first and fourth on the other list. Thus one letter position remains the same for the two contingencies, a fact which seems to produce interference, not facilitation.
Perseveration of Responses In an attempt to obtain clarification of the general lack of facilitation and of the interference in the one case, an analysis of all responses coming from the total set during the first four transfer trials was made. The total set contains 16 words, and each learned subset contains eight, with four words being the same on the first and second lists. This arrangement means that the total set of 16 words can be broken into four meaningful quarters (or subsets of four) for the second task: ( + + ) , the words in both first and second subsets; ( - + ) , the words in the second but not in the first subset; ( + - ) , the words in the first but not in the second subset; and ( - - ) , the words in neither subset. For second learning, the first two subsets of four contain the correct words, and the sec-
ond two subsets contain the incorrect words. The mean number of responses in second learning from each of these quarters is shown in Table 2. For every condition, more correct responses, ( + + ) and ( - - + ), came from the quarter of the total set which was also in the first subset. Furthermore, for every condition, more errors, ( + - - ) and ( - - ) , came from the quarter of the total set which was in the first subset. Thus these results show that there is indeed perseveration of individual word TABLE MEAN NUMBER OF RESPONSES PER TRIAL FROM EACH QUARTER OF THE TOTAL SET OF WORDS IN FIRST FOUR TRIALS OF TRANSFER LEARNING Quarter a Condition 8-S (a) b S-S (b) S-C (a a n d b) C-S (a a n d b) C-C
(++) ~.88 8.5~ ~.56 8.50 ~.58
(-+) ~.8~ 8.87 ~.00 8.19 1.91
(+-) 1.~8 0.55 1.49 0.5~ 1.59
(--) 1.~0 0.80 1.21 0.48 0.94
a (++), words on b o t h lists; ( - - + ) , words on second b u t n o t on first list; ( + - - ) , words on first b u t n o t on zeeond list; a n d ( - - - ) , words on neither
list. b N's are shown in Table 1. responses from first learning to transfer learning; but of equal if not greater importance is the very small amount of it, and the circumstances under which it is greatest. The interaction between conditions and location of responses is significant. Part of this interaction is simply due to the fact that all conditions do not produce equal errors. But another part of the interaction is due to the nature of the structure of the second task, with simple structure of the second task producing less perserveration than complex structure. For correct responses, the largest differences in source
926
GARNER AND DEGER]!VlAN
of responses, ( + q - ) vs. ( - q - ) , came from the two conditions having complex structure on the transfer task. For incorrect responses, the largest differences in source of responses, ( q - - ) vs. ( - - - ) , came from these same two conditions. These results indicate that in general these lists of words are learned as structured subsets, not as individual words. Thus when a new subset is presented, the fact that four of the words were previously part of another subset is somewhat irrelevant. However, the fact that more perserverative responses occurred when a subset with complex structure was being learned suggests that such subsets come closer to being learned as lists of individual items rather than as structured sets. This conclusion is strengthened by the fact that the greatest amount of perseveration (with both correct responses and errors) occurred when the first and the second lists both had complex structure. DISCUSSION
This experiment, as well as previous ones, make clear that flee-recall learning is not primarily a process of learning individual items, but is a process of learning sets of items and their structure. In this series of experiments, the structure lies in the actual construction of the nonsense words. The structure may lie in semantic meaning, however, if real words are used rather than nonsense words, but here also it is becoming clear that learning is not of individual words, but of sets of words. Tulving (1966), for example, has shown that learning part of a list of real words does not facilitate later learning of the total list (a repetitive part procedure), and he explains the results as being due to S's use of a different subjective organization for the part than for the total list. An additional factor, however, is now evident in regard to the transfer problem.
Garner and Whitman (1965) showed that learning a total set of nonsense words is easier than learning a subset, and Cohen (1968) has shown that it is easier to learn all the words of a given category of meaning than to learn just part of the words. Furthermore, Garner and Whitman also showed that there is facilitation in learning a total set when a subset with simple structure has first been learned, and this result with a repetitive part procedure is contrary to that of Tulving. The difference seems most clearly related to the fact that Tulving's whole lists of words did not constitute meaningful total sets (they were randomly selected English nouns), and it seems likely that if his repetitive part procedure had been used with whole lists which constituted meaningful total sets ( such as all the words in a given category ) he would have obtained facilitation in the learning of the whole lists. In the present experiment, neither of the two lists to be learned, nor the two lists taken together, constituted total sets. Thus our obtained lack of facilitation is consistent with the generalization that facilitation will occur only when the learning tasks involve a total set of words, either because the second task is the total set or because the two tasks together use the total set. Even this generalization must be restricted to the use of subsets with simple structure, because the subsets with complex structure do not facilitate learning the structure of the total set. REFERENCES
CorIEN, B. H. Recall of categorized word lists. ]. exp. Psychol., 1963, 66, 227-234. GARNEa, W. R. Uncertainty and structure as psychological concepts. New York: Wiley, 1962. GAP~En, W. R., AND WmTMaN, J. R. Form and amount of internal structure as factors in free-recall learning of nonsense words. 1. verb. Learn. verb. Behav., 1965, 4, 257-266. TULVING, E. Subjective organization and effects of repetition in multitrial free-recall learning.
TRANSFER WITH OVERLAPPING LISTS
J. verb. Learn. verb. Behav., 1966, 5, 198197. WmTX~AN, J. R., aND GARNER, W. R. Free-recall learning of visual figures as a function of form of internal structure. J. exp. Psychol., 196:29, 64, 558-564.
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WHITM[AN, J. R., AND GARNEa, W. t~. Concept learning as a function of form of internal structure. 1. verb. Learn. verb. Behav., 1963, 2, 195-202. (Received May 16, 1966)
(1967)
Transfer in Free-Recall Learning of Overlapping Lists of Nonsense Words 1 W. R. GARNER AND RICHARD L. DEGERMAN Johns Hopkins University, Baltimore, Maryland 21218 The Ss were required to learn a list of eight nonsense words which was a subset from a total set of 16, and then to learn another subset of eight which contained four words from the original list. Learning diflqculty was found to be determined almost entirely by whether the internal structure of the subset was simple or complex. No facilitation in learning the second subset was found. Interference occurred when both the first and second subsets had one simple contingency between two letter positions and both contingencies involved a letter position in common. It is concluded that facilitation will occur only when the total learning task involves a meaningful total set of words, with a structure of the subsets perceived as related to the structure of the total set. Garner (1962) has pointed out that freerecall learning involves learning the properties of sets or subsets of items. More specifically, Garner and Whitman (1965) argued that the free-recall process is concerned with three levels of stimulus sets: The total set is the set of stimuli generated by orthogonal combinations of all the variables which define the stimuli, and learning of a total set of nonsense words involves learning all the letters which can occur at each letter position. The actual set is a subset of the total set, and is the set presented for learning. When the actual set is smaller than the total set, a structure exists, within the subset, that consists of relations between the variables making up the stimuli. This internal structure may be simple, consisting of contingencies between various pairs of letter positions, or it may be complex, consisting of interactions involving three or 1 This research was supported in part by grant MHl1062 from the National Institute of Mental Health to Johns Hopkins University. The senior author is now at Yale University.
more letter positions. Whitman and Garner (1962, 1968) and Garner and Whitman (1965) have shown that subsets with simple structure are much easier to learn than subsets with complex structure. The individual stimulus can be considered a third level of stimulus set, since each stimulus is also a subset of the total set. Whitman and Garner (1962, 1968), however, have shown that the rate at which a particular geometric pattern is learned is entirely a question of the properties of the larger subset of which it is a part, and has nothing to do with any unique properties of the individual stimulus. This conclusion is further strengthened by the finding of Garner and Whitman (1965) that learning of a total set of words prior to learning of a subset does not facilitate learning of the subset. In this latter study, which involved transfer as well as original learning, facilitation on the second task occurred only when the original learning was of a subset of eight from the total set of 16 words, when that subset had a simple form of
922
TRANSFER WITH OVERLAPPING LISTS structure, a n d w h e n the second l e a r n i n g i n v o l v e d either the c o m p l e m e n t of t h e o r i g i n a l subset or the total set itself. T h u s facilitation o c c u r r e d only w h e n the second set of words was the same size as the first, or i n c l u d e d the first set. Moreover, i n b o t h of these cases l e a r n i n g of t h e total set was involved, either b y use of the total set for s e c o n d l e a r n i n g or b y use of the complem e n t of the first set for the second learni n g task. Purpose of Experiment. The p r e s e n t exp e r i m e n t was d e s i g n e d to explore this p r o b l e m f u r t h e r b y r e q u i r i n g free-recall l e a r n i n g of n o n s e n s e words in t h e transfer p a r a d i g m , b u t w i t h first a n d second sul~sets w h i c h are the s a m e size a n d i n c l u d e some of the same words. T h e t w o subsets to b e l e a r n e d consist of eight words, four of w h i c h are t h e same, so t h a t 12 words are l e a r n e d i n the t w o tasks. T h e subsets are selected from a total set of 16. T h u s l e a r n i n g of the total set is n o t required. METHOD
Words The total set of nonsense words was the same as that used by Garner and Whitman (1965) and consisted of the 16 words which can be formed from all combinations of each of two letters in each of four letter positions. The first letter could be B or P, the second R or L, the third A or O, and the fourth J or Z. The subsets to be learned always consisted of eight of these words, claosen to have different kinds of internal structure as indicated below.
General Procedure Each S was run individually in a room with the only other person present, seated across a table from him. Each word was printed on a card with block capital letters 32-mm high and was shown to S by E one word at a time, in random order, With exposure time per word of 5 see. During this time S read the letters aloud. Immediately after seeing the last word in a set, S was required to write the words down, in any order. He was allowed 60 sec to reproduce the words and was encouraged to guess. After each trial the words were presented again in a dif-
E,
923
ferent random order, and trials were continued until S reached criterion of a correct reproduction of the eight words two trials in succession. However, trials were terminated without complete learning after 15, and no S was continued for more than 1 hr total time. This latter restriction prevented completion in a few cases. All Ss were undergraduate students at Johns Hopkins from the Introductory Psychology course.
Experimental Conditions All conditions required S to learn eight words on first leaming, then eight on second learning, with four of the eight words being the same on both lists. Thus half of the second list consisted of words from the first list. The experimental variations concerned the form of the internal structure in each of the two lists, with either a simple structure involving a single pair contingency or a complex structure involving an interaction uncertainty. Simple-Simple (S-S). (a) The two lists of words were: BLAJ, BLAZ, BLOJ, BLOZ, PRAJ, PRAZ, PROJ, PROZ and BLAJ, BLOJ, BRAJ, BROJ, PLAZ, PLOZ, PRAZ, PROZ. The first list has a pair contingency between the first two letter positions, and the second list has a pair contingency between the first and the fourth letter positions. Ten Ss were used for this condition, half learning each list first. (b) The two lists were: BRAJ, BRAZ, BROJ, BROZ, PLAJ, PLAZ, PLOJ, PLOZ and BLAZ, BLOJ, BRAZ, BROJ, PLAZ, PLOJ, PRAZ, PROJ. The first list has a pair contingency between the first two letter positions, and the second list has a pair contingency between the last two letter positions. Ten Ss were used for this condition, half learning each list first. Simple-Complex (S-C). (a) The two lists of words were: BRAJ, BRAZ, BROJ, BROZ, PLAJ, PLAZ, PLOJ, PLOZ and BLAJ, BLOZ, BRAJ, BROZ, PLAZ, PLOJ, PRAZ, PROJ. The first list has a pair contingency between the first two letter positions and the second list has an interaction involving the first, third, and fourth letter positions. Ten Ss were run on this condition, with the list with simple structure learned first. (b) The first list of words was the same as for S-C (a) with a pair contingency between the first two letter positions. The second list was: BLAJ, BLOZ, BRAZ, BROJ, PLAZ, PLOJ, PRAJ, PROZ. This second list has an interaction involving all four letter positions. Ten Ss were run on this condition, with the list with simple structure learned first.
924
GARNER AND DEGERMAN
Statistical analyses showed no significant differences 2 between S-C (a) and S-C (b), so resuits are presented for these 20 Ss as a single group. Complex-Simple (C-S). (a) and (b) C-S (a) used the stone word lists as S-C (a), but in the reverse order, and C-S (b) used the same word lists as S-C (b), but in the reverse order. Ten Ss were used for each subcondition, but since again statistical analyses showed no significant differences between the two conditions, results are presented for these 20 Ss as a single group. Complex-Complex (C-C). The two lists were: BLAZ, BLOJ, BRAJ, BROZ, PLAZ, PLOJ, PRAJ, PROZ, and BLAJ, BLOZ, BRAJ, BROZ, PLAZ, PLOJ, PRAZ, PROJ. The first list has an interaction involving the last three letter positions, and the second list has an interaction involving the first, third, and fourth letter positions. Five Ss were run with the two lists in the indicated order and three Ss were run with the lists in the reverse order.
RESULTS
The results were analyzed with a variety of measures: total errors, trials to criterion, learning curves, and correct recalls during the first four learning trials. The various measures all lead to the same conclusions, but results are presented only in terms of correct recalls during the first four trials, with any trials after criterion counted as entirely correct. The use of this measure gives somewhat greater sensitivity in showing transfer effects, and that was the primary concern of the experiment. In addition, it avoids some of the statistical instability produced by skewed distributions for total errors or trials to criterion.
First Learning Table 1 shows the results for first learning. On first learning, the major effect is that the subsets of eight words with simple structure are much easier to learn than subsets with complex structure. W i t h simple ~All statements of statistical significance are based on analysis of variance, at 5% level of significance.
TABLE 1 PERCENTAGE OF WORDS CORRECTLY RECALLED IN FIRST FOUR LEARNING TRIALS
Learning order Condition
N
1
,S-S (a) S-S (b) S-C (a and b) C-S (a and b) C-C
10 10 ~0 ~0 8
83.8 85.9 90.9 58.8 64.1
65.0 86.1 57.0 83.6 55.5
structure, the percentages correct on first four trials ranged from about 84 to 91, while the two conditions starting with complex structure gave percentages of about 59 and 64. This result completely confirms that found previously by Garner and Whitman (1965). Altogether three different forms of complex structure were used, one with an interaction between all four letter positions, one with an interaction between the first, third, and fourth letter positions, and one with an interaction between the last three letter positions. With this last type of interaction (used for five Ss in the C-C condition) the percentage of correct recalls was approximately 75, and was significantly greater than for the other two complex structures. Within the simple forms of structure, three different pair contingencies were used, involving the first two, the last two, or the first and last letter positions. There were no statistically significant differences in difficulty of initial learning for these three types. Nevertheless, there were slight differences, with a contingency between the first two le~er positions being easier to learn. Even though this difference is not statistically significant, in conjunction with the easier learning of an interaction contingency involving the last three letter positions, it suggests that learning of any
925
TRANSFER W / T H OVERLAPPING LISTS
structure is easier if the structure involves adjacent letter positions.
Transfer Learning The results for the second learning task are also shown in Table 1. With the exception of the S-S (a) condition, there is no evidence for either facilitation or interference in the transfer task: the difficulty of learning the second list of words depends entirely on the structure involved in that list of words and not at all on the structure of t h e first list of words. There is substantial and significant negative transfer for the S-S (a) conditibn, with the second subset being almost as difficult to learn as the subsets with complex structure. This condition is one in which a pair contingency between the first two letter positions exists on one list and a pair contingency between the first and fourth on the other list. Thus one letter position remains the same for the two contingencies, a fact which seems to produce interference, not facilitation.
Perseveration of Responses In an attempt to obtain clarification of the general lack of facilitation and of the interference in the one case, an analysis of all responses coming from the total set during the first four transfer trials was made. The total set contains 16 words, and each learned subset contains eight, with four words being the same on the first and second lists. This arrangement means that the total set of 16 words can be broken into four meaningful quarters (or subsets of four) for the second task: ( + + ) , the words in both first and second subsets; ( - + ) , the words in the second but not in the first subset; ( + - ) , the words in the first but not in the second subset; and ( - - ) , the words in neither subset. For second learning, the first two subsets of four contain the correct words, and the sec-
ond two subsets contain the incorrect words. The mean number of responses in second learning from each of these quarters is shown in Table 2. For every condition, more correct responses, ( + + ) and ( - - + ), came from the quarter of the total set which was also in the first subset. Furthermore, for every condition, more errors, ( + - - ) and ( - - ) , came from the quarter of the total set which was in the first subset. Thus these results show that there is indeed perseveration of individual word TABLE MEAN NUMBER OF RESPONSES PER TRIAL FROM EACH QUARTER OF THE TOTAL SET OF WORDS IN FIRST FOUR TRIALS OF TRANSFER LEARNING Quarter a Condition 8-S (a) b S-S (b) S-C (a a n d b) C-S (a a n d b) C-C
(++) ~.88 8.5~ ~.56 8.50 ~.58
(-+) ~.8~ 8.87 ~.00 8.19 1.91
(+-) 1.~8 0.55 1.49 0.5~ 1.59
(--) 1.~0 0.80 1.21 0.48 0.94
a (++), words on b o t h lists; ( - - + ) , words on second b u t n o t on first list; ( + - - ) , words on first b u t n o t on zeeond list; a n d ( - - - ) , words on neither
list. b N's are shown in Table 1. responses from first learning to transfer learning; but of equal if not greater importance is the very small amount of it, and the circumstances under which it is greatest. The interaction between conditions and location of responses is significant. Part of this interaction is simply due to the fact that all conditions do not produce equal errors. But another part of the interaction is due to the nature of the structure of the second task, with simple structure of the second task producing less perserveration than complex structure. For correct responses, the largest differences in source
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GARNER AND DEGER]!VlAN
of responses, ( + q - ) vs. ( - q - ) , came from the two conditions having complex structure on the transfer task. For incorrect responses, the largest differences in source of responses, ( q - - ) vs. ( - - - ) , came from these same two conditions. These results indicate that in general these lists of words are learned as structured subsets, not as individual words. Thus when a new subset is presented, the fact that four of the words were previously part of another subset is somewhat irrelevant. However, the fact that more perserverative responses occurred when a subset with complex structure was being learned suggests that such subsets come closer to being learned as lists of individual items rather than as structured sets. This conclusion is strengthened by the fact that the greatest amount of perseveration (with both correct responses and errors) occurred when the first and the second lists both had complex structure. DISCUSSION
This experiment, as well as previous ones, make clear that flee-recall learning is not primarily a process of learning individual items, but is a process of learning sets of items and their structure. In this series of experiments, the structure lies in the actual construction of the nonsense words. The structure may lie in semantic meaning, however, if real words are used rather than nonsense words, but here also it is becoming clear that learning is not of individual words, but of sets of words. Tulving (1966), for example, has shown that learning part of a list of real words does not facilitate later learning of the total list (a repetitive part procedure), and he explains the results as being due to S's use of a different subjective organization for the part than for the total list. An additional factor, however, is now evident in regard to the transfer problem.
Garner and Whitman (1965) showed that learning a total set of nonsense words is easier than learning a subset, and Cohen (1968) has shown that it is easier to learn all the words of a given category of meaning than to learn just part of the words. Furthermore, Garner and Whitman also showed that there is facilitation in learning a total set when a subset with simple structure has first been learned, and this result with a repetitive part procedure is contrary to that of Tulving. The difference seems most clearly related to the fact that Tulving's whole lists of words did not constitute meaningful total sets (they were randomly selected English nouns), and it seems likely that if his repetitive part procedure had been used with whole lists which constituted meaningful total sets ( such as all the words in a given category ) he would have obtained facilitation in the learning of the whole lists. In the present experiment, neither of the two lists to be learned, nor the two lists taken together, constituted total sets. Thus our obtained lack of facilitation is consistent with the generalization that facilitation will occur only when the learning tasks involve a total set of words, either because the second task is the total set or because the two tasks together use the total set. Even this generalization must be restricted to the use of subsets with simple structure, because the subsets with complex structure do not facilitate learning the structure of the total set. REFERENCES
CorIEN, B. H. Recall of categorized word lists. ]. exp. Psychol., 1963, 66, 227-234. GARNEa, W. R. Uncertainty and structure as psychological concepts. New York: Wiley, 1962. GAP~En, W. R., AND WmTMaN, J. R. Form and amount of internal structure as factors in free-recall learning of nonsense words. 1. verb. Learn. verb. Behav., 1965, 4, 257-266. TULVING, E. Subjective organization and effects of repetition in multitrial free-recall learning.
TRANSFER WITH OVERLAPPING LISTS
J. verb. Learn. verb. Behav., 1966, 5, 198197. WmTX~AN, J. R., aND GARNER, W. R. Free-recall learning of visual figures as a function of form of internal structure. J. exp. Psychol., 196:29, 64, 558-564.
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WHITM[AN, J. R., AND GARNEa, W. t~. Concept learning as a function of form of internal structure. 1. verb. Learn. verb. Behav., 1963, 2, 195-202. (Received May 16, 1966)