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Response factors in verbal learning and transfer
JOURNAL OF VERBALLEARNINGAND VERBALBEHAVIOR11, 234-238 (1972)
Response Factors in Verbal Learning and Transfe# DOUGLAS L. MED1N The Rockefeller Umversity, New York, New York 10021 Two experiments investigated the role of responses m organizing unrelated stimulus materials and altering performance in shift paradigms In Exp. I free ret,all tests given after paired-associate training involving unrelated stimulus words mapped onto single-digit responses in a 4: l ratio showed sigmficant clustering arouna the response members For Exp. II Ss learned unrelated word-number paired-associate hsts (again mapped 4.1), whereupon the required responses were shifted, but the new pairings left the responsedefined categories undisturbed. SubJects displayed positive transfer on the basis of response-created categories. Learning on the final word-letter hst demonstrated responsedefined within-category errors equal in magnitude to stimulus-defined within-category errors of control groups.
After learning to sort two sets of conceptually related stimuli (e.g., animals and colors) into separate categories, Ss are able to execute a reversal shift faster than a half-reversal shift. In a reversal shift, the S must switch his sorting responses for all items in each category; while in a half-reversal shift, the response is switched for only half the items of each category. The superiority of reversal shifts over nonreversal shifts has often been attributed to the use of representational responses (stimulus dimensions) which provide mediated cues that are appropriate for reversal shifts but inappropriate for half-reversal shifts (Kendler, Kendler & Sanders, 1967; Kendler, Kendler & Marken, 1969). However, in many of these experiments purportedly assessing stimulus mediation, response mediation (e.g., for a reversal, using the rule make the opposite response from before) has been a potentially confounding variable. Several investigators have found reversal shifts to be superior to half-reversal shifts even when the stimulus items did not fall into categories or dimensions (Bogartz, 1965; Paul, 1966; Paul & Paul, 1968; Sanders, 1971). These results as well as previous work by this 1 This research was supported by USPHS Grant GM16735 from the National Institute of General Medical Sciences. 234 © 1972 by AcademmPress, Ine.
author (Medxn, 1970) support the suggestion that associations concerning previous correctness and incorrectness of items may themselves provide class-level cues which can either facilitate or impair shift performance. The present experiments further examined the role which response variables might play an organizing verbal materials. In the first experiment, Ss received word-number pairedassociate training involving 16 different words paired with four different responses (single digits). Following paired-associate training, Ss were given a free recall test on the stimulus words. The four unrelated words paired with each digit were considered to be a category, and clustering in recall was assessed in terms of these response-defined categories. A related experiment by Runquist (1970) has shown that similarity of stimulus words in wordword paired-associate lists produces clustering on this basis when Ss are given free recall tests on the unrelated response words. EXPERIMENT I
Method Subjects. Seven female and five male college students who responded to advertisements m a local newspaper (The Village Voice) served an the experiment. The Ss ranged m age between 17 and 24 and had not served in previous learning experiments. All Ss were paid $2 00 for the 30-min test session.
VERBAL LEARNING AND TRANSFER. RESPONSE FACTORS Apparatus. Subjects were seated m front of an ASR33 teletype which was interfaced with a PDP-8/I computer. Stimulus materials were printed out on the teletype, and Ss responded by pressing keys on the teletype keyboard For paired-associate training, single digit numbers were used for responses, for the free recall tests, the teletype acted as a type,~nter The computer randomized the stimulus-outcome pairrags, controlled the various snmulus and reward sequences and recorded Ss' responses. Sttmulus matertals The stimuli were 16 common four-letter nouns The nouns were chosen so as to be unrelated to each other (e g, WOLF, DECK, POLE, NOON). Single digits (1-8) served as response members for training. For a given S, four of the eight possible responses were randomly chosen for the pmred-assocmte trmls. Each of the four single dig~t responses was paired with four different unrelated words for the paired-associate training Procedure SubJects were given 16 runs through the 16-item noun-number list They were told to associate the words with the numbers and were told which four digits would serve as admissible responses Snmulus orders for each run were randomly determined A given trial proceeded as follows" (1) The teletype printed out a word, (2) the S made his response, (3) the teletype printed out the word again along with the number paired with it, and (4) a 1.5-sec lntertrial interval ensued The presentanon of the word-number pmr always awmted the S's response. Following pmred-assoclate training, the experimenter chatted with the S for a minute in order to eliminate any short-term memory for the stimulus words, then asked the S to type out as many of the words as he could remember SubJects were gwen 5 mm for the free recall test. Results and Discussion Subjects a v e r a g e d 54.8 errors d u r i n g the p a i r e d - a s s o c i a t e trials a n d all but one S perf o r m e d perfectly by the last r u n t h r o u g h the list. T h e other S reached 14 out o f 16 correct responses and the free recall d a t a to be rep o r t e d are for all 12 Ss. I n spite o f the fact that there was no a d v a n c e notice t h a t a free recall test w o u l d be given, Ss p e r f o r m e d quite well, averaging 13.2 w o r d s recalled out o f a possible score o f 16. Clusterm g was assessed by a runs test ( F r a n k e l & Cole, 1971), a measure which as fairly indep e n d e n t o f the total n u m b e r o f w o r d s recalled. This measure yields a Z score (with a p o p u l a tion m e a n o f 0 a n d a s t a n d a r d deviation o f 1).
235
The categories to which the runs test was applied were response-defined. T h a t is, two words were scored as c o m i n g f r o m the same category if they h a d been p a i r e d with the same response for p a i r e d - a s s o c i a t e training. Thus, p o t e n n a l l y there were four categories each having four m e m b e r s Subjects showed strong clustering a r o u n d these response-defined categories The average Z score was 1.33, yielding a g r o u p Z score o f 4.61, which is very highly significant. This result lmphes that the responses served to organize the unrelated w o r d s for recall in m u c h the same m a n n e r as similar s n m u l u s ~tems did m the e x p e r i m e n t o f R u n q u i s t (1970) previously mentioned.
EXPERIMENT II The first e x p e r i m e n t showed that responses can act in a slmllar m a n n e r to stimulus d i m e n sions in at least one way, namely, to organize the recall o f unrelated words. The second study e x a m i n e d d i s c r i m i n a t i o n shifts a n d withincategory errors a l o n g a response dxmensmn. Subjects received w o r d - n u m b e r p a i r e d - a s s o clate training on 16 w o r d - n u m b e r pairs as m the first experiment, but now, after Ss met a learning criterion, the response m e m b e r s changed. The new pairings left the responsedefined categories u n d i s t u r b e d - - t h a t is, all the w o r d s p a i r e d with a given n u m b e r d u r i n g the first stage o f training w o u l d n o w be p a i r e d with the same new response. Subjects might be expected to p e r f o r m a b o v e chance on the first trial o f a shift, if they were able to use the initial responses to o r g a m z e the list. A f t e r three such shifts, Ss were given a final p a i r e d - a s s o c i a t e task using the same 16 stimuli b u t with 16 single letters serving as responses. T h e variable o f p r i m a r y interest was the nature o f the errors Ss m a d e d u r i n g learning. T y p i c a l l y when stimulus d i m e n s i o n s are e m p l o y e d in p a i r e d - a s s o c i a t e training, a large p r o p o r t i o n o f errors are f o u n d to be w i t h i n - d i m e n s i o n o r c a t e g o r y errors (W. Runquist, 1966, 1968; P. Runquist, 1970).
236
MEDtN
T h a t is, a s u b s t a n t m l n u m b e r
of erroneous
responses were those responses which were approprmte
to other stimuli within the same
category or &mensaon. In the present experim e n t , c a t e g o r a e s w e r e r e s p o n s e - d e f i n e d according to the word-number training pairs and within-category errors were assessed on t h i s basis. I n o t h e r w o r d s , i f a n e r r o n e o u s response consisted of a letter which was appropriate to a word which had had the same d i g i t s p a i r e d wath at d u r i n g p r e t r a i n i n g , it w a s s c o r e d as a w i t h i n - c a t e g o r y e r r o r . F o r t h e final list, S s w e r e e i t h e r t o l d w h i c h 16 o f t h e p o s s i b l e s i n g l e l e t t e r r e s p o n s e s w o u l d b e u s e d o r w e r e t o l d samply t h a t 16 d i f f e r e n t l e t t e r s w o u l d b e e m p l o y e d as r e s p o n s e s . A pilot study suggested that this might be a significant variable affecting within-category errors.
Method Subjects The experiment employed 26 female and 22 male college students who responded to advertisements in a local newspaper (The Village Votce). Subjects were paid $2 00 for the 50-rain test session. The Ss were randomly assigned to one of four treatment groups. Because of computer failures, the data from two Ss from Groups I, II and IV and from one S in Group III were lost, leaving 10 Ss in three groups and 11 Ss in Group III Apparatus. The ASR-33 teletype and the PDP-8/I computer used in the first study were again employed Snmulus materials Stimuli were common fourletter nouns For Group I and Group II, the words were 16 unrelated nouns, while for Group III and Group IV, the nouns were eight names of girls and eight animal names All nouns were four-letter words Single digits (1-8) served as response members m training for Group I and Group II For a given problem, two digits were paired with the 16 words (eight words for each digit), and for each S at the end of original training and three shift problems, all eight possible digits had been employed. Single alphabetical characters were used for the final test for Group I and Group II and for the single list given Group III and Group IV. Procedure. Group I and Group II received identical training untd the final hst Both groups were trained on an imtml paired-associate problem using the 16 unrelated nouns as stimulus words, were given three shift problems employing the same words and digits for responses, and finally were trained on the same word list but with 16 different alphabetical characters as
responses For the original problem, Ss were given standard paired-associate instructions and were told which two digits (randomly selected for each subject) would serve as admissible responses. SubJects were instructed to guess on the first run through the list Stimulus orders for each run through the list were randomly determined. Subjects were trained to a criterion of one perfect run before being given the shift problems A 30-sec interval lapsed between a S meeting criterion on one problem and the start of a shift problem During this time Ss were told that the new problem would revolve the same words but that now they would have to learn to associate digit X and &glt Y (two new digits) with the words The experimenter again reformed Ss that initially they would have to guess but eventually they should be able to supply the correct dlglt for each word. Although Ss were not reformed of this, a simple pattern governed the wordnumber pairings for the shift problems. The eight words that had been paired with one of the digits on the original problem (the response-defined category) were all paired with the same new digit on the shift problem. After the S met the criterion of one perfect run on the shift problem, he was given another shift problem employing two new digits. Again the Ss were given the same lnstruchons and the word-number pairings followed the simple pattern just described. In all, Ss m both groups received three shift problems, so that for each subject the response digits 1-8 were exhausted After meeting criterion on the original problem and three shift problems, Group I and Group II Ss were trained to the same criterion on a paired-associate list involving the same words as before with 16 single alphabetical characters as responses SubJects were told that 16 different letters would be used and that they had been learning a hst of 16 words which meant that no letter would be pmred with more than one word These instructions were designed to eliminate withincategory errors that might arise if Ss thought that emght of the words would have the same response (as in the previous problems). For Group I, the 16 letters serwng as responses were randomly selected and Ss initially did not know which 16 letters would be employed Group II was told exactly which 16 letters would serve as responses (the bottom two rows of the teletype) and consequently knew the set of letters at the start of the final problem In other words, Group II was not required to do any response learning The only pmred-assoclate problem given Group III and Group IV was hke the final problem for Group I and Group II except that the stimulus words fell into two categories (girls names and animal names) Group III and Group IV were designed to assess within category errors attributable to stimulus categories and compare them with the category errors (with a category
VERBALLEARNINGAND TRANSFER:RESPONSEFACTORS being response-defined) for Group I and Group II. Group IlI was most slmdar to Group I in that Ss were not told which 16 response letters would be used, whde Group IV was similar to Group II. Finally at the end of these problems, Ss m all groups were asked to type out as many of the words as they could remember. The recall test was administered exactly as m the first experiment
Results and Discussion The first data of interest are the performance of Group I and Group II on the three shift problems. Since these groups were not treated differentially at this point in testing, only combined results will be reported. If Ss /tre able to utilize the response-defined categories on the shift problems, one might expect performance to be above chance on the first run of a shift problem. That is, the S may use a rule such as "all words having response 3, now have response 8." Indeed performance was substantially above chance on the first run for each of the shift problems. Subjects averaged 77 ~ correct on Trial 1 of the first shift, 87 ~o for the second shift, and 89 ~ correct on the third shift. Two of the 20 Ss said they had not noticed the pattern to the shifts and their performance never surpassed a guessing level of 50 ~ correct on first runs through the lists. The second variable of major concern is the proportion of within-category errors. The average total errors on the word-letter pair-
ings for the four groups was quite similar and ranged from 58.6 to 77.5. A within-category error was defined as guessing a letter which was appropriate to another word from the same stimulus category for Group III and Group IV and as guessing a letter appropriate to another word from the same responsedefined grouping or category for Group I and Group II. Within-category errors were compared with extracategory errors, and errors which were responses appropriate to no stimulus word (for Group I and Group III) were not considered in these comparisons. By chance, 7 out of 15 or a .467 proportion of within-category errors should be observed (ignoring extrahst errors). Table 1 shows the observed proportion of within-category errors and the percentage above the chance proportion of withincategory errors which these figures represent. Compared to previous experiments, the proportion of within-category errors is quite small. However, a definite pattern to these results emerges. The groups which were told exactly which responses were permlssxble showed a proportion of within-category errors which was very close to the chance expectation. The group not told the set of permissible responses did show a significant proportion of within-category errors. Response-defined category errors were at least as prominent as stimulus category errors. The proportion of
TABLE I PROPORTION OF LIST ERRORS WHICH ARE WITHIN-CATEGORYERRORS (STANDARD DEVIATIONS IN PARENTHESES) AND THE PERCENTAGE ABOVE CHANCE THESE FIGURES REPRESENT FOR EACH OF THE FOUR GROUPS
Group I (response categories, response set unspecified) Group II (response categories, response set specified) Group III (stimulus categories, response set unspecified) Group IV (stimulus categories, response set specified)
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Proportion w~thln-category errors
Percentage abovechance
.547 (089) .482 (.084) .520 (107) .473 (.059)
15.4 3.2 11.4 1.3
238
MEDIN
within-category errors is statistically reliable, t(9)=2.82, p < . 0 2 , for Group I and approaches significance for Group III, t(10)= 1.60, .05 < p < .10. The mean number of words recalled on the free recall test ranged from 14.4 to 15.4 out of a possible 16 for the four groups. The wordletter training virtually abolished category clustering in the free recall tests. The group Z scores ranged from -.71 for Group II to 1.69 for Group IV, the latter being marginally significant. These scores are substantially lower than the group Z score of 4.61 observed in the first experiment.
which is directly available. When the set of responses is unknown or incompletely specified, the S may be forced to scan his memory in search of permissible responses, and perhaps hls memory or search organization is such as to be likely to produce within-category errors. In any event, in this experiment the prominence of within-category errors for response categories was as large as that produced by stimulus categories, which further supports the contention that responses may play a significant role in organizing verbal materials.
General Discussion
BOGARTZ,W. Effects of reversal and nonreversal shifts with CVC stlmuh. Journal of Verbal Learning and Verbal Behavior, 1965, 1, 484-488. FRANKEL, F., • COLE, M. Measures of category clustering m free recall Psychological Bulletin, 1971, 76, 39--44 KENDLER, H. H , KENDLER, T. S., & MARKEN, R. S. Developmental analysis of reversal and halfreversal shifts Developmental Psychology, 1969, 1, 318-326. KENDLER, H. H , KENDLER, T. S., & SANDERS, J Reversal and partial reversal shifts with verbal
These experiments lend further support to the contention that response factors are a significant variable in verbal shift paradigms. The first study demonstrated that Ss' free recall was clustered significantly around response-defined categories. The second experiment established that these categories can greatly facilitate shift performance and, in the case of Group I, can produce an above-chance proportion of within-category errors. In other words, response-defined categories exhibit many of the properties often attributed to stimulus categories. This result suggests that it may be of value to reexamine previous studies which varied both stimulus and response categories, but restricted theoretical discussions to the former variable. It is interesting to speculate as to why knowledge of the specific set of responses appears to be a crucial variable determining the occurrence of within-category errors. The previous experiments showing much larger effects used response sets which were completely unknown to the Ss at the start of training. In the present study within category errors occurred only when Ss were required to learn which 16 of 26 possible letters would be used. Perhaps when the S has the permissible set of responses directly in front of himself and is uncertain of the correct response, he simply guesses randomly from this set of responses
REFERENCES
material. Journal of Verbal Learning and Verbal Behavior, 1967, 6, 117-127. MEDIN, D. L. Emergent conceptual cues in multiple item verbal discrimination learning. Rockefeller University Technical Report, 1970. PAUL, C. Verbal &scrimination reversal as a function of overlearning and percentage of 1terns reversed. Journal of Experimental Psychology, 1966, 72, 271-275 PAUL, C., & PAUL, H. Transfer-activated response sets m verbal learning and transfer. Psychologtcal Review, 1968, 75, 537-549. RUNQUIST, P. A. Clustering m free recall following paired-assooate learning. Journal of Experimental Psychology, 1970, 83, 260-265. RUNQUIST,W N. Intralist interference as a function of list length and mterstlmulus similarity. Journal of Verbal Learmng and Verbal Behavior, 1966, 5, 7-13. RUNQUIST, W. N. Reversal vs. nonreversal re-pamng in categorized paired-associate hsts. Canadian Journal of Psychology, 1968, 22, 285-293 SANDERS,B. Factors affecting reversal and nonreversal shifts m rats and children JournalofComparative andPhysiologicalPsychology, 1971,74, 192-202. (Received September 17, 1971)
Response Factors in Verbal Learning and Transfe# DOUGLAS L. MED1N The Rockefeller Umversity, New York, New York 10021 Two experiments investigated the role of responses m organizing unrelated stimulus materials and altering performance in shift paradigms In Exp. I free ret,all tests given after paired-associate training involving unrelated stimulus words mapped onto single-digit responses in a 4: l ratio showed sigmficant clustering arouna the response members For Exp. II Ss learned unrelated word-number paired-associate hsts (again mapped 4.1), whereupon the required responses were shifted, but the new pairings left the responsedefined categories undisturbed. SubJects displayed positive transfer on the basis of response-created categories. Learning on the final word-letter hst demonstrated responsedefined within-category errors equal in magnitude to stimulus-defined within-category errors of control groups.
After learning to sort two sets of conceptually related stimuli (e.g., animals and colors) into separate categories, Ss are able to execute a reversal shift faster than a half-reversal shift. In a reversal shift, the S must switch his sorting responses for all items in each category; while in a half-reversal shift, the response is switched for only half the items of each category. The superiority of reversal shifts over nonreversal shifts has often been attributed to the use of representational responses (stimulus dimensions) which provide mediated cues that are appropriate for reversal shifts but inappropriate for half-reversal shifts (Kendler, Kendler & Sanders, 1967; Kendler, Kendler & Marken, 1969). However, in many of these experiments purportedly assessing stimulus mediation, response mediation (e.g., for a reversal, using the rule make the opposite response from before) has been a potentially confounding variable. Several investigators have found reversal shifts to be superior to half-reversal shifts even when the stimulus items did not fall into categories or dimensions (Bogartz, 1965; Paul, 1966; Paul & Paul, 1968; Sanders, 1971). These results as well as previous work by this 1 This research was supported by USPHS Grant GM16735 from the National Institute of General Medical Sciences. 234 © 1972 by AcademmPress, Ine.
author (Medxn, 1970) support the suggestion that associations concerning previous correctness and incorrectness of items may themselves provide class-level cues which can either facilitate or impair shift performance. The present experiments further examined the role which response variables might play an organizing verbal materials. In the first experiment, Ss received word-number pairedassociate training involving 16 different words paired with four different responses (single digits). Following paired-associate training, Ss were given a free recall test on the stimulus words. The four unrelated words paired with each digit were considered to be a category, and clustering in recall was assessed in terms of these response-defined categories. A related experiment by Runquist (1970) has shown that similarity of stimulus words in wordword paired-associate lists produces clustering on this basis when Ss are given free recall tests on the unrelated response words. EXPERIMENT I
Method Subjects. Seven female and five male college students who responded to advertisements m a local newspaper (The Village Voice) served an the experiment. The Ss ranged m age between 17 and 24 and had not served in previous learning experiments. All Ss were paid $2 00 for the 30-min test session.
VERBAL LEARNING AND TRANSFER. RESPONSE FACTORS Apparatus. Subjects were seated m front of an ASR33 teletype which was interfaced with a PDP-8/I computer. Stimulus materials were printed out on the teletype, and Ss responded by pressing keys on the teletype keyboard For paired-associate training, single digit numbers were used for responses, for the free recall tests, the teletype acted as a type,~nter The computer randomized the stimulus-outcome pairrags, controlled the various snmulus and reward sequences and recorded Ss' responses. Sttmulus matertals The stimuli were 16 common four-letter nouns The nouns were chosen so as to be unrelated to each other (e g, WOLF, DECK, POLE, NOON). Single digits (1-8) served as response members for training. For a given S, four of the eight possible responses were randomly chosen for the pmred-assocmte trmls. Each of the four single dig~t responses was paired with four different unrelated words for the paired-associate training Procedure SubJects were given 16 runs through the 16-item noun-number list They were told to associate the words with the numbers and were told which four digits would serve as admissible responses Snmulus orders for each run were randomly determined A given trial proceeded as follows" (1) The teletype printed out a word, (2) the S made his response, (3) the teletype printed out the word again along with the number paired with it, and (4) a 1.5-sec lntertrial interval ensued The presentanon of the word-number pmr always awmted the S's response. Following pmred-assoclate training, the experimenter chatted with the S for a minute in order to eliminate any short-term memory for the stimulus words, then asked the S to type out as many of the words as he could remember SubJects were gwen 5 mm for the free recall test. Results and Discussion Subjects a v e r a g e d 54.8 errors d u r i n g the p a i r e d - a s s o c i a t e trials a n d all but one S perf o r m e d perfectly by the last r u n t h r o u g h the list. T h e other S reached 14 out o f 16 correct responses and the free recall d a t a to be rep o r t e d are for all 12 Ss. I n spite o f the fact that there was no a d v a n c e notice t h a t a free recall test w o u l d be given, Ss p e r f o r m e d quite well, averaging 13.2 w o r d s recalled out o f a possible score o f 16. Clusterm g was assessed by a runs test ( F r a n k e l & Cole, 1971), a measure which as fairly indep e n d e n t o f the total n u m b e r o f w o r d s recalled. This measure yields a Z score (with a p o p u l a tion m e a n o f 0 a n d a s t a n d a r d deviation o f 1).
235
The categories to which the runs test was applied were response-defined. T h a t is, two words were scored as c o m i n g f r o m the same category if they h a d been p a i r e d with the same response for p a i r e d - a s s o c i a t e training. Thus, p o t e n n a l l y there were four categories each having four m e m b e r s Subjects showed strong clustering a r o u n d these response-defined categories The average Z score was 1.33, yielding a g r o u p Z score o f 4.61, which is very highly significant. This result lmphes that the responses served to organize the unrelated w o r d s for recall in m u c h the same m a n n e r as similar s n m u l u s ~tems did m the e x p e r i m e n t o f R u n q u i s t (1970) previously mentioned.
EXPERIMENT II The first e x p e r i m e n t showed that responses can act in a slmllar m a n n e r to stimulus d i m e n sions in at least one way, namely, to organize the recall o f unrelated words. The second study e x a m i n e d d i s c r i m i n a t i o n shifts a n d withincategory errors a l o n g a response dxmensmn. Subjects received w o r d - n u m b e r p a i r e d - a s s o clate training on 16 w o r d - n u m b e r pairs as m the first experiment, but now, after Ss met a learning criterion, the response m e m b e r s changed. The new pairings left the responsedefined categories u n d i s t u r b e d - - t h a t is, all the w o r d s p a i r e d with a given n u m b e r d u r i n g the first stage o f training w o u l d n o w be p a i r e d with the same new response. Subjects might be expected to p e r f o r m a b o v e chance on the first trial o f a shift, if they were able to use the initial responses to o r g a m z e the list. A f t e r three such shifts, Ss were given a final p a i r e d - a s s o c i a t e task using the same 16 stimuli b u t with 16 single letters serving as responses. T h e variable o f p r i m a r y interest was the nature o f the errors Ss m a d e d u r i n g learning. T y p i c a l l y when stimulus d i m e n s i o n s are e m p l o y e d in p a i r e d - a s s o c i a t e training, a large p r o p o r t i o n o f errors are f o u n d to be w i t h i n - d i m e n s i o n o r c a t e g o r y errors (W. Runquist, 1966, 1968; P. Runquist, 1970).
236
MEDtN
T h a t is, a s u b s t a n t m l n u m b e r
of erroneous
responses were those responses which were approprmte
to other stimuli within the same
category or &mensaon. In the present experim e n t , c a t e g o r a e s w e r e r e s p o n s e - d e f i n e d according to the word-number training pairs and within-category errors were assessed on t h i s basis. I n o t h e r w o r d s , i f a n e r r o n e o u s response consisted of a letter which was appropriate to a word which had had the same d i g i t s p a i r e d wath at d u r i n g p r e t r a i n i n g , it w a s s c o r e d as a w i t h i n - c a t e g o r y e r r o r . F o r t h e final list, S s w e r e e i t h e r t o l d w h i c h 16 o f t h e p o s s i b l e s i n g l e l e t t e r r e s p o n s e s w o u l d b e u s e d o r w e r e t o l d samply t h a t 16 d i f f e r e n t l e t t e r s w o u l d b e e m p l o y e d as r e s p o n s e s . A pilot study suggested that this might be a significant variable affecting within-category errors.
Method Subjects The experiment employed 26 female and 22 male college students who responded to advertisements in a local newspaper (The Village Votce). Subjects were paid $2 00 for the 50-rain test session. The Ss were randomly assigned to one of four treatment groups. Because of computer failures, the data from two Ss from Groups I, II and IV and from one S in Group III were lost, leaving 10 Ss in three groups and 11 Ss in Group III Apparatus. The ASR-33 teletype and the PDP-8/I computer used in the first study were again employed Snmulus materials Stimuli were common fourletter nouns For Group I and Group II, the words were 16 unrelated nouns, while for Group III and Group IV, the nouns were eight names of girls and eight animal names All nouns were four-letter words Single digits (1-8) served as response members m training for Group I and Group II For a given problem, two digits were paired with the 16 words (eight words for each digit), and for each S at the end of original training and three shift problems, all eight possible digits had been employed. Single alphabetical characters were used for the final test for Group I and Group II and for the single list given Group III and Group IV. Procedure. Group I and Group II received identical training untd the final hst Both groups were trained on an imtml paired-associate problem using the 16 unrelated nouns as stimulus words, were given three shift problems employing the same words and digits for responses, and finally were trained on the same word list but with 16 different alphabetical characters as
responses For the original problem, Ss were given standard paired-associate instructions and were told which two digits (randomly selected for each subject) would serve as admissible responses. SubJects were instructed to guess on the first run through the list Stimulus orders for each run through the list were randomly determined. Subjects were trained to a criterion of one perfect run before being given the shift problems A 30-sec interval lapsed between a S meeting criterion on one problem and the start of a shift problem During this time Ss were told that the new problem would revolve the same words but that now they would have to learn to associate digit X and &glt Y (two new digits) with the words The experimenter again reformed Ss that initially they would have to guess but eventually they should be able to supply the correct dlglt for each word. Although Ss were not reformed of this, a simple pattern governed the wordnumber pairings for the shift problems. The eight words that had been paired with one of the digits on the original problem (the response-defined category) were all paired with the same new digit on the shift problem. After the S met the criterion of one perfect run on the shift problem, he was given another shift problem employing two new digits. Again the Ss were given the same lnstruchons and the word-number pairings followed the simple pattern just described. In all, Ss m both groups received three shift problems, so that for each subject the response digits 1-8 were exhausted After meeting criterion on the original problem and three shift problems, Group I and Group II Ss were trained to the same criterion on a paired-associate list involving the same words as before with 16 single alphabetical characters as responses SubJects were told that 16 different letters would be used and that they had been learning a hst of 16 words which meant that no letter would be pmred with more than one word These instructions were designed to eliminate withincategory errors that might arise if Ss thought that emght of the words would have the same response (as in the previous problems). For Group I, the 16 letters serwng as responses were randomly selected and Ss initially did not know which 16 letters would be employed Group II was told exactly which 16 letters would serve as responses (the bottom two rows of the teletype) and consequently knew the set of letters at the start of the final problem In other words, Group II was not required to do any response learning The only pmred-assoclate problem given Group III and Group IV was hke the final problem for Group I and Group II except that the stimulus words fell into two categories (girls names and animal names) Group III and Group IV were designed to assess within category errors attributable to stimulus categories and compare them with the category errors (with a category
VERBALLEARNINGAND TRANSFER:RESPONSEFACTORS being response-defined) for Group I and Group II. Group IlI was most slmdar to Group I in that Ss were not told which 16 response letters would be used, whde Group IV was similar to Group II. Finally at the end of these problems, Ss m all groups were asked to type out as many of the words as they could remember. The recall test was administered exactly as m the first experiment
Results and Discussion The first data of interest are the performance of Group I and Group II on the three shift problems. Since these groups were not treated differentially at this point in testing, only combined results will be reported. If Ss /tre able to utilize the response-defined categories on the shift problems, one might expect performance to be above chance on the first run of a shift problem. That is, the S may use a rule such as "all words having response 3, now have response 8." Indeed performance was substantially above chance on the first run for each of the shift problems. Subjects averaged 77 ~ correct on Trial 1 of the first shift, 87 ~o for the second shift, and 89 ~ correct on the third shift. Two of the 20 Ss said they had not noticed the pattern to the shifts and their performance never surpassed a guessing level of 50 ~ correct on first runs through the lists. The second variable of major concern is the proportion of within-category errors. The average total errors on the word-letter pair-
ings for the four groups was quite similar and ranged from 58.6 to 77.5. A within-category error was defined as guessing a letter which was appropriate to another word from the same stimulus category for Group III and Group IV and as guessing a letter appropriate to another word from the same responsedefined grouping or category for Group I and Group II. Within-category errors were compared with extracategory errors, and errors which were responses appropriate to no stimulus word (for Group I and Group III) were not considered in these comparisons. By chance, 7 out of 15 or a .467 proportion of within-category errors should be observed (ignoring extrahst errors). Table 1 shows the observed proportion of within-category errors and the percentage above the chance proportion of withincategory errors which these figures represent. Compared to previous experiments, the proportion of within-category errors is quite small. However, a definite pattern to these results emerges. The groups which were told exactly which responses were permlssxble showed a proportion of within-category errors which was very close to the chance expectation. The group not told the set of permissible responses did show a significant proportion of within-category errors. Response-defined category errors were at least as prominent as stimulus category errors. The proportion of
TABLE I PROPORTION OF LIST ERRORS WHICH ARE WITHIN-CATEGORYERRORS (STANDARD DEVIATIONS IN PARENTHESES) AND THE PERCENTAGE ABOVE CHANCE THESE FIGURES REPRESENT FOR EACH OF THE FOUR GROUPS
Group I (response categories, response set unspecified) Group II (response categories, response set specified) Group III (stimulus categories, response set unspecified) Group IV (stimulus categories, response set specified)
237
Proportion w~thln-category errors
Percentage abovechance
.547 (089) .482 (.084) .520 (107) .473 (.059)
15.4 3.2 11.4 1.3
238
MEDIN
within-category errors is statistically reliable, t(9)=2.82, p < . 0 2 , for Group I and approaches significance for Group III, t(10)= 1.60, .05 < p < .10. The mean number of words recalled on the free recall test ranged from 14.4 to 15.4 out of a possible 16 for the four groups. The wordletter training virtually abolished category clustering in the free recall tests. The group Z scores ranged from -.71 for Group II to 1.69 for Group IV, the latter being marginally significant. These scores are substantially lower than the group Z score of 4.61 observed in the first experiment.
which is directly available. When the set of responses is unknown or incompletely specified, the S may be forced to scan his memory in search of permissible responses, and perhaps hls memory or search organization is such as to be likely to produce within-category errors. In any event, in this experiment the prominence of within-category errors for response categories was as large as that produced by stimulus categories, which further supports the contention that responses may play a significant role in organizing verbal materials.
General Discussion
BOGARTZ,W. Effects of reversal and nonreversal shifts with CVC stlmuh. Journal of Verbal Learning and Verbal Behavior, 1965, 1, 484-488. FRANKEL, F., • COLE, M. Measures of category clustering m free recall Psychological Bulletin, 1971, 76, 39--44 KENDLER, H. H , KENDLER, T. S., & MARKEN, R. S. Developmental analysis of reversal and halfreversal shifts Developmental Psychology, 1969, 1, 318-326. KENDLER, H. H , KENDLER, T. S., & SANDERS, J Reversal and partial reversal shifts with verbal
These experiments lend further support to the contention that response factors are a significant variable in verbal shift paradigms. The first study demonstrated that Ss' free recall was clustered significantly around response-defined categories. The second experiment established that these categories can greatly facilitate shift performance and, in the case of Group I, can produce an above-chance proportion of within-category errors. In other words, response-defined categories exhibit many of the properties often attributed to stimulus categories. This result suggests that it may be of value to reexamine previous studies which varied both stimulus and response categories, but restricted theoretical discussions to the former variable. It is interesting to speculate as to why knowledge of the specific set of responses appears to be a crucial variable determining the occurrence of within-category errors. The previous experiments showing much larger effects used response sets which were completely unknown to the Ss at the start of training. In the present study within category errors occurred only when Ss were required to learn which 16 of 26 possible letters would be used. Perhaps when the S has the permissible set of responses directly in front of himself and is uncertain of the correct response, he simply guesses randomly from this set of responses
REFERENCES
material. Journal of Verbal Learning and Verbal Behavior, 1967, 6, 117-127. MEDIN, D. L. Emergent conceptual cues in multiple item verbal discrimination learning. Rockefeller University Technical Report, 1970. PAUL, C. Verbal &scrimination reversal as a function of overlearning and percentage of 1terns reversed. Journal of Experimental Psychology, 1966, 72, 271-275 PAUL, C., & PAUL, H. Transfer-activated response sets m verbal learning and transfer. Psychologtcal Review, 1968, 75, 537-549. RUNQUIST, P. A. Clustering m free recall following paired-assooate learning. Journal of Experimental Psychology, 1970, 83, 260-265. RUNQUIST,W N. Intralist interference as a function of list length and mterstlmulus similarity. Journal of Verbal Learmng and Verbal Behavior, 1966, 5, 7-13. RUNQUIST, W. N. Reversal vs. nonreversal re-pamng in categorized paired-associate hsts. Canadian Journal of Psychology, 1968, 22, 285-293 SANDERS,B. Factors affecting reversal and nonreversal shifts m rats and children JournalofComparative andPhysiologicalPsychology, 1971,74, 192-202. (Received September 17, 1971)