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Clustering with perceptual and symbolic stimuli in free recall
JOURNAL OF VERBAL LEARNING AND VERBAL BEHAVIOR 6, 8 6 4 - - 8 6 6
(1967)
Clustering with Perceptual and Symbolic Stimuli in Free Recall 1 KEITI-I G . S C O T T 2
University of Connecticut, Storrs, Connecticut Two groups of undergraduates were compared in their free recall of perceptual (object) and symbolic (word) stimuli. It was found that the absolute n u m b e r of perceptual stimuli recalled was significantly greater than the absolute n u m b e r of symbolic stimuli recalled. By statistically controlling for the absolute amount of recall it was demonstrated that the perceptual stimuli also showed a significantly greater tendency to cluster than the symbolic stimuli.
Corer (1965) has recently pointed to the need for an exhaustive study of the tasks and situations that delineate the variables that control the strength of associations and category relations. One such class of variables is the type of stimuli used. Two prominent kinds of stimuli are those distinguished by Underwood (1952) as perceptual and symbolic. Perceptual stimuli are exemplified by objects or pictures; symbolic stimuli are exemplified by words. The present study compares the free recall of perceptual and symbolic stimuli using objects that, according to pretests, were given a consistent verbal label. METHOD
Subiects. Ninety unpaid members of undergraduate psychology classes served as Ss to meet a course requirement. They were assigned randomly to two groups of 45 each, one for the word stimuli and the other for the object stimuli. 1 This study was supported in part by Grant M1099 from the National Institute of Mental Health. Professor David Zeaman kindly made facilities and help available. Now at the University of Illinois. The study grew out of independent course work under the direction of Professor Weston A. Bousfield whose encouragement is gratefully acknowledged. The writer is indebted to Amy Gilbert who acted as E. 864
Stimulus Materials. To select suitable stimulus items 54 small common objects that belonged to such categories as toy vehicles and animals were placed in random order on a large table. Fifteen psychology graduate students were given sheets of paper with the lines numbered to correspond to nmnbers attached to the objects. They were instructed to write the name of each object using one, or at most two, words. The sheets were analyzed to find objects that were consistently labeled. Seven objects, to which all Ss gave an identical label, or to which 14 Ss gave an identical label and 1 S gave a dearly similar l~ibel were selected from each of four categories. For example, 14 Ss wrote "DRILLS," and 1 S wrote "AUGER." The 28 objects selected in the four categories were: FILE, SAW, DRILL, PLIERS, WRENCH, HAMMER, SCREWDRIVER; PEN, ENVELOPE, BLOTTER, PENCIL, STAPLER, COMPASS, ERASER; AIRPLANE, CAR, JEEP, TRUCK, MOTORCYCLE, TRAIN, TRACTOR; DOG, HIPPOPOTAMUS, PIG, MONKEY, RABBIT, BEAR, TURTLE. Corresponding to each object the name given it was printed in letters one-half in. high in black, on a plain white 6 × 4 in. file card. Apparatus. The Ss sat in front of a turntable that was arranged so that one segment was exposed at a time. The objects or words were placed centrally on a turntable segment for presentation. The word-cards stood on stands so as to be inclined to S's view. Procedure. From 1 to 4 Ss took part in each experimental session in which either objects or words were presented. Thirteen different lists of the stimuli were used. Each list was used for the same
CLUSTERING AND R E C A L L number of Ss from the object and word groups. No list was used for more than 4 Ss from each group. The lists were in random order except for the restriction that no two words from the same category ever followed each other. The E first distributed lined pads with a pen attached. The Ss were instructed to recall the words or objects they were about to see in any order, listing them against the left-hand margin of the sheet. The E then went behind the screens and presented the stimuli by placing them on the turntable and rotating it every 5 sec when a light flashed, to the next segment and stimulus. The list of 28 stimuli was presented only once to the S. Five min were allowed for recall.
865
in learning, and Otto (1962) found that children's responses to perceptual stimuli were different in both number and kind. Various interpretations of the present data are possible. One interpretation would suppose that perceptual stimuli provide a greater number of cues than do symbolic stimuli. This means they are more distinctive during learning since they differ in many respects in addition to their labels. They are thus more readily learned. Secondly, since there is an abundance of cues which are conditioned during learning, the loss of some associations by the time of reRESULTS call is less serious than with a more imThe mean number of words recalled poverished stimulus which is more likely was 17.9 for the Word Group and 20.7 for to drop below the recall threshold. Finally the Object Group, t ( 8 8 ) = 4.4, p < .01. the abundance of cues provides many opThe unit for clustering, a repetition, is deportunities for both direct and mediated fined as the sequential occurence of two associative hookup and thus facilitates clusitems in the same category. The mean tering. Another possibility would be that number of clusters was 3.8 for the Word the objects possess higher interitem assoGroup and 4.9 for the Object Group. The ciations than the words and thus show difference is highly significant, t ( 8 8 ) greater recall and clustering. A definitive = 4.07, p < .01. The mean number of obinterpretation will require further data on served repetitions was 8.5 for the Word other sets of stimuli and information about Group and 11.8 for the Object Group. The the relevant association data. expected chance clustering E (SCR) was Of particular methodological importance calculated by the formula: is the demonstrated sensitivity of percep~W?I2 -q- Tf2~ • . • ~/k 2 tual stimuli, suggesting that they are ideal E(SCR) = 1 n for use in developmental comparative Where m~ + . . . + m k represent the num- studies of clustering. When symbolic stimber of items recalled. The difference, ob- uli are used in the comparison of different served minus expected repetitions, is 4.8 developmental levels, or comparative for the Word Group and 7.5 for the Object studies of normal and retarded children, Group, and the difference between the reading attainment and clustering may be groups is highly significant, t ( 8 8 ) = 3.3, hopelessly confounded. This problem has p < .01. been met by the use of perceptual stimuli and vocal recall in a study by Bousfield, DISCUSSION Esterson and Whitmarsh (1958), and The results show clearly that perceptual should represent standard procedure with stimuli (objects) are both recalled better these Ss. and show a stronger tendency to cluster REFERENCES than symbolic stimuli (words). Wimer and Lambert (1959) have previously demon- BOUSFIELD~ W . A . , ESTERSON, S., AND W H I T M A R S I I , strated the superiority of perceptual stimuli G. A. A study of development changes in as-
866
SCOTT
sociative clustering. J. genet. Psyehol., 1958, 92, 95-102. COFER, C. N. On some factors in the organizational characteristics of free recall. Amer. Psychologist, 1965, 20, 261-272. OTto, W. The differential effects of verbal and pictorial representations of stimuli upon reJponses evoked, J. verb. Learn. verb. Behav., 1962, 1, 192--196.
UNOERWO00, B, J. An orientation for research on thinking. Psychol. Rev., 1952, 59, 209-220. WIMEn, C. C., and LAMBERT, W. E. The differential effects of word and object stimuli on the learning of paired associates. 1. exp. Psychol., 1959, 57, 31-86.
(Received March 21, 1966)
(1967)
Clustering with Perceptual and Symbolic Stimuli in Free Recall 1 KEITI-I G . S C O T T 2
University of Connecticut, Storrs, Connecticut Two groups of undergraduates were compared in their free recall of perceptual (object) and symbolic (word) stimuli. It was found that the absolute n u m b e r of perceptual stimuli recalled was significantly greater than the absolute n u m b e r of symbolic stimuli recalled. By statistically controlling for the absolute amount of recall it was demonstrated that the perceptual stimuli also showed a significantly greater tendency to cluster than the symbolic stimuli.
Corer (1965) has recently pointed to the need for an exhaustive study of the tasks and situations that delineate the variables that control the strength of associations and category relations. One such class of variables is the type of stimuli used. Two prominent kinds of stimuli are those distinguished by Underwood (1952) as perceptual and symbolic. Perceptual stimuli are exemplified by objects or pictures; symbolic stimuli are exemplified by words. The present study compares the free recall of perceptual and symbolic stimuli using objects that, according to pretests, were given a consistent verbal label. METHOD
Subiects. Ninety unpaid members of undergraduate psychology classes served as Ss to meet a course requirement. They were assigned randomly to two groups of 45 each, one for the word stimuli and the other for the object stimuli. 1 This study was supported in part by Grant M1099 from the National Institute of Mental Health. Professor David Zeaman kindly made facilities and help available. Now at the University of Illinois. The study grew out of independent course work under the direction of Professor Weston A. Bousfield whose encouragement is gratefully acknowledged. The writer is indebted to Amy Gilbert who acted as E. 864
Stimulus Materials. To select suitable stimulus items 54 small common objects that belonged to such categories as toy vehicles and animals were placed in random order on a large table. Fifteen psychology graduate students were given sheets of paper with the lines numbered to correspond to nmnbers attached to the objects. They were instructed to write the name of each object using one, or at most two, words. The sheets were analyzed to find objects that were consistently labeled. Seven objects, to which all Ss gave an identical label, or to which 14 Ss gave an identical label and 1 S gave a dearly similar l~ibel were selected from each of four categories. For example, 14 Ss wrote "DRILLS," and 1 S wrote "AUGER." The 28 objects selected in the four categories were: FILE, SAW, DRILL, PLIERS, WRENCH, HAMMER, SCREWDRIVER; PEN, ENVELOPE, BLOTTER, PENCIL, STAPLER, COMPASS, ERASER; AIRPLANE, CAR, JEEP, TRUCK, MOTORCYCLE, TRAIN, TRACTOR; DOG, HIPPOPOTAMUS, PIG, MONKEY, RABBIT, BEAR, TURTLE. Corresponding to each object the name given it was printed in letters one-half in. high in black, on a plain white 6 × 4 in. file card. Apparatus. The Ss sat in front of a turntable that was arranged so that one segment was exposed at a time. The objects or words were placed centrally on a turntable segment for presentation. The word-cards stood on stands so as to be inclined to S's view. Procedure. From 1 to 4 Ss took part in each experimental session in which either objects or words were presented. Thirteen different lists of the stimuli were used. Each list was used for the same
CLUSTERING AND R E C A L L number of Ss from the object and word groups. No list was used for more than 4 Ss from each group. The lists were in random order except for the restriction that no two words from the same category ever followed each other. The E first distributed lined pads with a pen attached. The Ss were instructed to recall the words or objects they were about to see in any order, listing them against the left-hand margin of the sheet. The E then went behind the screens and presented the stimuli by placing them on the turntable and rotating it every 5 sec when a light flashed, to the next segment and stimulus. The list of 28 stimuli was presented only once to the S. Five min were allowed for recall.
865
in learning, and Otto (1962) found that children's responses to perceptual stimuli were different in both number and kind. Various interpretations of the present data are possible. One interpretation would suppose that perceptual stimuli provide a greater number of cues than do symbolic stimuli. This means they are more distinctive during learning since they differ in many respects in addition to their labels. They are thus more readily learned. Secondly, since there is an abundance of cues which are conditioned during learning, the loss of some associations by the time of reRESULTS call is less serious than with a more imThe mean number of words recalled poverished stimulus which is more likely was 17.9 for the Word Group and 20.7 for to drop below the recall threshold. Finally the Object Group, t ( 8 8 ) = 4.4, p < .01. the abundance of cues provides many opThe unit for clustering, a repetition, is deportunities for both direct and mediated fined as the sequential occurence of two associative hookup and thus facilitates clusitems in the same category. The mean tering. Another possibility would be that number of clusters was 3.8 for the Word the objects possess higher interitem assoGroup and 4.9 for the Object Group. The ciations than the words and thus show difference is highly significant, t ( 8 8 ) greater recall and clustering. A definitive = 4.07, p < .01. The mean number of obinterpretation will require further data on served repetitions was 8.5 for the Word other sets of stimuli and information about Group and 11.8 for the Object Group. The the relevant association data. expected chance clustering E (SCR) was Of particular methodological importance calculated by the formula: is the demonstrated sensitivity of percep~W?I2 -q- Tf2~ • . • ~/k 2 tual stimuli, suggesting that they are ideal E(SCR) = 1 n for use in developmental comparative Where m~ + . . . + m k represent the num- studies of clustering. When symbolic stimber of items recalled. The difference, ob- uli are used in the comparison of different served minus expected repetitions, is 4.8 developmental levels, or comparative for the Word Group and 7.5 for the Object studies of normal and retarded children, Group, and the difference between the reading attainment and clustering may be groups is highly significant, t ( 8 8 ) = 3.3, hopelessly confounded. This problem has p < .01. been met by the use of perceptual stimuli and vocal recall in a study by Bousfield, DISCUSSION Esterson and Whitmarsh (1958), and The results show clearly that perceptual should represent standard procedure with stimuli (objects) are both recalled better these Ss. and show a stronger tendency to cluster REFERENCES than symbolic stimuli (words). Wimer and Lambert (1959) have previously demon- BOUSFIELD~ W . A . , ESTERSON, S., AND W H I T M A R S I I , strated the superiority of perceptual stimuli G. A. A study of development changes in as-
866
SCOTT
sociative clustering. J. genet. Psyehol., 1958, 92, 95-102. COFER, C. N. On some factors in the organizational characteristics of free recall. Amer. Psychologist, 1965, 20, 261-272. OTto, W. The differential effects of verbal and pictorial representations of stimuli upon reJponses evoked, J. verb. Learn. verb. Behav., 1962, 1, 192--196.
UNOERWO00, B, J. An orientation for research on thinking. Psychol. Rev., 1952, 59, 209-220. WIMEn, C. C., and LAMBERT, W. E. The differential effects of word and object stimuli on the learning of paired associates. 1. exp. Psychol., 1959, 57, 31-86.
(Received March 21, 1966)