Verb facilitation of paired-associate learning as a function of syntactic and semantic relations

JOURNAL OF VERBAL LEARNING AND VERBAL BEFIAV[OR8, 773-781

(1969)

V e r b Facilitation of Paired-Associate Learning as a Function of Syntactic and Semantic Relations I LINNEA C. EHRI AND WILLIAM D. ROHWER, JR.

University of California, Berkeley 94720 Fourth- and fifth-grade children were given a PA learning task. Experimental groups were exposed to nouns linked by verbs (sentences), while the control group saw conjunctionlinked nouns. Effects of three independent variables were assessed: semantic relation of the verb with its nouns, test-trial stimuli, and verb construction. Performance varied as a function of the verb relation and test stimulus factors. Results suggest that verbs, in order to produce better noun-pair learning than conjunctions, must be aroused during the test trial so that they can expedite retrieval of verb phrases where object nouns are stored. Also, the findings indicate that verbs can cue recall as well as nouns and that verb-preposition connectives have the same effect on performance as verbs.

Recent investigations by Rohwer and asso- duced no corresponding decrement in learning. ciates (Rohwer, 1967) have explored factors In another study, Rohwer and Levin (1968) which facilitate the learning of lists of paired compared action and still verbs and found no English nouns. These studies have found that evidence for differential facilitation as a the ease of learning nouns embedded in function of the amount of overt activity meaningful, grammatical word strings is a described by the verbs. Also, no facilitation function of the type of form-class connective occurred when nouns were linked by verbs in linking the two nouns. That is, learning ways which violated semantic selectional improves when the nouns are joined by a verb restrictions (for example, Fingers break days). rather than a preposition, and by a preposition Rohwer (1966) investigated two other types rather than a conjunction. The present study of sentence anomalies. N o u n pairs were aims to extend the investigation of factors embedded in strings containing either synwhich enhance or limit this form-class effect. tactically marked nonsense syllables or English and to offer a tentative explanation. words. Syntactic structure was either obliPrevious attempts to manipulate charac- terated by scrambling, or preserved by orderteristics of the verb connective have been un- ing, the words and markers. Only true successful in producing differential facilitation sentences, acceptable syntactically and lexiin learning as a function of specific verb caUy, produced facilitation of noun-pair properties. Rohwer and Lynch (1967) exa- learning. The foregoing findings suggest that mined the effects of intralist verb similarity in order for the form-class effect to obtain, by varying the number of different verbs (2, strings must be grammatically, lexically, and 4, or 8) linking the noun pairs. Surprisingly, semantically acceptable and that additional more extensive intralist verb repetition pro- variations in specific verb properties do not significantly alter this general level of facilita1 This work was supported in part by a contract tion produced by verb connectives. with the NatioIial Science Foundation (GB-8026). The The present study proposes to investigate report was prepared at the Institute of Human Learnsome functional aspects of verbs and to ing, which is supported by grants from the National suggest that the functions which are critical Institutes of Health. 773

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their capacity to serve as test stimuli. Given the presentation of pairs of nouns in sentence contexts, examination of this variable involves a procedure in which learners are provided with either the subject noun or the verb unit or the two together as cues for retrieval of the object noun. Interest in this variable is aroused by contradictions found in previous research regarding the effect of the verb's presence during recall. Whereas Rohwer, Shuell, and Levin (1967) showed that inclusion of the verb with the initial noun as the test stimulus enhanced performance over that occurring when the noun was presented alone, Rohwer and Levin (1968) did not find this additional facilitation. Furthermore, in the latter study, the presentation of verbs w~thout subject nouns as test stimuli produced a deterioration in recall below that of the control group, and it was concluded that verbs, unlike nouns, do not function effectively as test stimuli. However, since the presentation format for nouns and verbs was not equivalent, this matter of the verb's functional value as a test stimulus should be examined further. Still another verb variation is of interest. Whereas past studies have utilized transitive verbs exclusively, the present study includes verb-preposition connectives. The factor, verb 2 In his discussion of formal grammars, Chomsky (1965) distinguishes between the deep and surface construction, is used to examine the effects of structures of sentences. Whereas the surface structure variations in the connective's formal properdescribes the sequence of syntactic units readied for ties, as opposed to its relational properties phonological interpretation, the deep structure iden- discussed above. Two types of connectives tifies those structural units and relations necessary for a r e employed: one-unit transitive verbs, a semantic interpretation. Phrase structure rules define the grammatical units or categories (for example, and two-unit verb-preposition combinations. Sentence, Noun Phrase, Verb Phrase) making up Various hypotheses supply a basis for making sentences, and rules of transformation operate on these alternative predictions regarding the differenelements to derive the surface from the deep structure. tial effects of these two verb types on learning. The organization of phrase constituents in the deep The unit hypothesis, which a~sumes that the structure, unlike that in the surface structure, specifies the grammatical relations existing among the phrase addition of more units produces an increase constituents. The cqncept Subject is specified as a in the amount of material to be processed and relation between a NP and an immediately dominating thus an increase in the length of time required Sentence, and the notion Object refers to a relation for learning, predicts that the one-unit verb, between an NP and an immediately dominating VP. given equivalent exposure time, should result Thus, aspects of the deep structure are crucial for determining the meaning of the sentence, while aspects in more learning than the two-unit verb. The in the surface structure signal the syntax relevant for linguistic complexity hypothesis makes the phonetic transmission of the sentence. same prediction but for different reasons, It for facilitation involve the specification of relations. That is, verbs, unlike conjunctions, impose the grammatical relations of subject and object upon the first and second nouns in a sentence. As such, each noun serves as part of one of the constituent phrases specified in the sentence's base structure. 2 Thus embedded in such structural units during learning, later recall of the nouns is aided by the rearousal of these syntactic relations. The present study manipulates syntactic structure in two ways, by contrasting verb with conjunction connectives, and by varying the probability of verb phrase arousal during recall. Not only do verbs impose syntactic relations on nouns, but they also enhance semantic relations among words in the sentence by arousing their c o m m o n and reciprocal semantic markers. Manipulation of semantic relations is accomplished in the present study by selecting two types of verbs for each noun pair, one type which is maximally related to its subject, the first noun, and minimally related to its object, the second noun, and one type where these relations are reversed. These are referred to as subject-related and objectrelated verbs, respectively. Another functional aspect of verbs involves

VERB FACILITATIONOF P A LEARNING argues that the i n t r o d u c t i o n of prepositional phrases increases the phrase-structure complexity a n d thus the processing difficulty of the sentence. The third hypothesis reverses the foregoing prediction for the reason that it regards verbs a n d prepositions as special types of connective units which serve to elaborate the n o u n s ahd thus m a k e learning easier. The e l a b o r a t i o n hyi~othesis is inferred f r o m the / i n d i n g b y Rohwer, Lynch, Levin, a n d Suzuki (1967) that b o t h prepositions a n d verbs can each e n h a n c e learning more t h a n conjunctions. A s s u m i n g that these effects are additive, that is, each connective contributes a certain a m o u n t of elaboration, this hypothesis predicts that verbs c o m b i n e d with prepositions p r o m o t e more learning t h a n verbs alone. Thus, the factor verb c o n s t r u c t i o n is included to determine whether facilitation occurs with a n o t h e r type of verb connective a n d whether the relative a m o u n t is greater or less than that o b t a i n e d with o n e - u n i t verbs used in previous studies. T o review, the aims of the present study were to discover whether verb connectives regardless of type facilitate n o u n - p a i r learning more t h a n c o n j u n c t i o n s , whether verbs can f u n c t i o n as effectively as n o u n s in p r o m p t i n g recall, whether the ability of verbs to aid retrieval is d e p e n d e n t o n their semantic relations with n o u n s , a n d whether the construction of the verb connective differentially influences learning. f

METHOD Design and Materials A design consisting of a 2 x 3 × 2 factorial with one outside control group was used to assess the influence of the three independent variables on performance in a paired-associate learning task. The first factor, verb relation, contrasted two contextual features of verbs, their semantic relation to either the subject noun (S-related verb) or the object noun (O-related verb) in sentences of the type S-V-O. The second factor, test stimulus, varied the extent to which parts of the sentence presented during the study trial were also presented during the test trial to cue recall: subject noun alone, verb alone, or subject noun and verb together. The third factor compared the relative effectiveness of two constructions of verb units, one-word transitive

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verbs or two-word verb-preposition combinations.The first two variables were manipulated by means of independent groups, while the third variable was examined through the use of mixed lists. A balanced set of grammatically and semantically acceptable sentences, that is, a set which contained the same noun pairs linked by each type of verb, was impossible to construct. Thus, only two sentences were written for each noun pair, one sentence containing an S-related verb and the other containing an Orelated verb. Half of each set of verbs consisted of oneword units and half were two-word verb-preposition units. While all the one-word units qualified as transitive verbs, taking direct objects, the two-word units were of mixed types, some transitive forms requiring a direct object (as The doctor laughs at the clown), and some intransitiveforms requiringan object for the preposition (as The candle hangs from the chain). Although one can attempt to distinguish these two types by examining whether meaning is preserved through a passive transformation, this separation was not incorporated as a regular feature of the design and so was not included in the analysis. Strings such as the following resulted: S-related, one-unit verb: The match burns the paint. O-related, one-unit verb: The match stirs the paint. S-related, two-unit verb" The horse gallops under the star. O-related, two-unit verb: The horse gazes at the star. Forty pairs of nouns were divided into two sets of 20 pairs, each set comparable in terms of noun frequency based on Thorndike-Lorge (1944) counts. Each noun pair was embedded in two different sentences, producing four lists of 20 sentences. WhereAs complete sentences were presented during the study trial, articles were omitted from the test stimulus and only content words (nouns and/or verb constructions) appeared as cues for recall of the object nouns. The control group, following exposure to noun pairs linked by the conjunctions and Or or, was tested with the first noun presented alone. All materials were typed on white memory-drum tape. Only final words of sentences, the nouns to be recalled, were capitalized in study-trial lists. All content words were underlined. The order of item presentation within each list was determined randomly, with a different order for study and test trials. Subjects The S sample consisted of 112 fourth- and fifthgraders drawn from a middle-class public elementary school. Eight children from each grade were randomly assigned to each of the seven conditions of the experiment.

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Procedure The learning task was administered individually in accord with a study-test method for one complete trial. Ss were instructed to remember the last word in each string so that it could be reproduced when a particular underlined word or words from that string appeared alone. Ss were told which type of test stimulus (N, V, or N & V) they would encounter and were given practice on three examples. The stimulus materials were presented on a memory drum at a 4-sec. rate. As the materials appeared, they were read aloud by the E. A 4-sec. delay occurred between the study and test trials. The Ss responded orally during the test trial. RESULTS Learning was measured in terms o f the number of nouns correctly recalled during the test trial. The results are presented in Figure 1, where the means reported are based on a m a x i m u m score o f 10 correct responses. A n analysis o f variance was performed on the results in a manner which allowed the variance associated with conditions to be partitioned so that all observations from both the control and experimental groups were included. (For the procedure, see Winer, 1963, p. 263.) Hypotheses were tested a t p < .01, and post

7 _ Test Cue 6 5 l// ,'
5 2" ~ /

2

×,.-~

f/.> × ).]. ,%/ •

0 Conj

S-Verb

O-Verb

Connective

FIG. 1. Mean number of responses correctly recalled as a function of the form class connective and the test cue.

hoc analyses were conducted at p < .05. A l t h o u g h none o f the main effects o f the factors was significant, the contrast between control and balanced design was, F ( 1 , 8 4 ) = 30.97, p < .01. Two o f the interactions were significant: Test S t i m u l i × V e r b Relation, F(2,84) = 7.64, p < .01, and Verb Construction × Lists, F(1,72) = 11.65,p < .01. 3 A matched-pair t test, performed on controlgroup scores in order to determine whether the nature o f the conjunction (and or or) differentially affected learning, disclosed no difference, t(15) = 1.80, p > .05. Examination of the interaction o f test stimulus with verb relation revealed that the a m o u n t recalled for the various test stimuli varied depending on whether the verb was o f the S- or the O-related type. Post hoc analyses using Scheffe's m e t h o d indicated that, in the O-related verb conditions, b o t h the V and the N V test stimuli each produced significantly greater learning than the N test stimuli, p < .05. The difference in recall between the V and the N V test stimuli was not significant. However, similar comparisons a m o n g the S-related verb conditions revealed no differences. Learning here was equivalent regardless of the nature o f the test cue. In order to determine whether facilitation was produced in the experimental conditions, D u n n e t t ' s test was employed. Results indicated that all groups but the one given Orelated verbs as connectives and subject nouns as test cues performed significantly better than the conjunction control group, p < .05. Furthermore, these results held regardless o f the nature o f the verb's construction. T h a t is, the same facilitation pattern displayed in Figure 1 was f o u n d for both one-unit verbs and two-unit verbs. Specifically, when performance with each o f the two verb types was separated out for each experimental g r o u p and contrasted with performance on the corresponding n o u n pairs in the control group, facilitation occurred in all conditions 3 The mean-square error for all between-subject effects was 6.03; for all within-subject effects, 1.89.

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but those given the combination of O-related verbs and N test cues. Thus, dearly one exception to the general finding of verb facilitation emerged, indicating that the presence of verbs as links for nouns during storage does not guarantee the facilitation of paired-associate learning: The nature of the relationship between the verb and its subject and object is critical. The comparison between experimental and control groups also revealed that the verb was able to function effectively as a test stimulus in facilitating recall, contrary to the findings of Rohwer and Levin (1968). The source of this discrepancy between studies can probably be attributed to differences in instructions or in presentation format. The present study forewarned subjects about the specific test stimulus which they would encounter and provided practice with it. Also, whereas Rohwer and Levin capitalized nouns but not verbs, the present study printed all words but the final noun in lower-case letters. Thus, format in this study gave no advantage to the subject noun. The interaction between verb construction and lists resulted from list differences for twounit but not for one-unit verbs as revealed by Scheffe's method of comparison. This might be a consequence of two facts: learning with List 2 nouns was slightly but not significantly easier than learning with List-1 nouns; and one-unit (transitive) verbs were less heterogeneous in type than two-unit verbs which consisted of intransitive as well as transitive connectives. However, the absence of further interactions of these with other variables affirms that list differences had little bearing on the main experimental results described above. DISCUSSION

The results make it clear that the nature of the verb's semantic relations with its nouns influences the learning process and that the amount of facilitation produced depends upon the test stimulus used to cue recall. Most out-

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standing among the results is the discovery of a verb type which erases the form-class effect. Previous studies have suggested that as long as the sentence is acceptable grammatically and semantically, any verb linking the two nouns will facilitate learning. However, it is now evident that object-related verbs produce no enhancement. Another notable finding is that verb-preposition connectives improve noun-pair learning as much as the one-unit transitive verbs which have been used exclusively in previous studies. With this, another form is added to the class of connectives known to facilitate learning. The third discovery, important because it contradicts a previous finding regarding the worth of the verb as a prompt for recall, indicates that verbs can cue recall as well as subject nouns, even verbs possessing minimal semantic overlap with their objects. A theoretical position which adopts linguistic constructs as psychological units of memory storage suggests a two-process explanation to account for the interaction between verb relation and test stimulus variables displayed in Figure 1. The enhancement of noun-pair learning produced by verbs can be viewed as resulting from (a) syntactic and (b) semantic processes. Syntactically, the verb locates the two nouns in grammatical categories (S, NP, VP) and imposes grammatical relations (subject and object) upon them. During learning, verb-linked nouns, unlike conjunction-linked nouns, enter memory storage as part of this grammatical structure, and later recall is facilitated by the residues of this structure as they are reinstated by the test stimulus. Memory storage and retrieval are also influenced by semantic processes under the control of the verb. Whereas S-related verbs arouse many semantic relations between themselves and the subject and few relations between themselves and the object, O-related verbs produce the reverse effect. Thus, following learning, when the task becomes one of retrieving the object noun, recall is a function of the likelihood that the test stimulus will

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arouse the verb phrase and its constituents, one of which is the object. Verb-induced facilitation of recall is insured when the verb is present during both the study and the test trials. However, when the verb does not appear and only the subject noun is present to cue recall, then the occurrence of facilitation is dependent upon whether this noun can elicit in memory the verb phrase. Subject nouns whose semantic overlap with their verb is maximal can easily arouse the verb phrase, whereas nouns possessing little semantic overlap with the verb cannot. This accounts for the success of nouns stored with S-related verbs and the failure of nouns stored with O-related verbs to enhance learning. Previous studies have established the importance of syntactic and semantic structures in the psychological processing of verbal stimuli. Johnson (1965) has shown that phrase structure rules reflect psychological encoding units as measured by higher transitional error probabilities at phrase boundaries in the recall of sentences. Blumentbal (1967) has demonstrated that grammatical relations specified in the deep structure are more important than surface structure segmentation in the learning of sentences. Ways of conceptualizing semantic structure have also been studied. Katz and Fodor (1964) develop the notion of semantic markers in their attempt to suggest the nature of the semantic component in a theory of language. Wordassociation data is used by Deese (1965) to compute the extent of associative overlap between words. Cofer (1965) examines the free recall response clustering of nouns produced by semantic similarities among adjectives which accompany the nouns during the study trial. The present study's use of the concept of semantic relations is intended to be compatible with the above semantic formulations although it neither quantifies nor elaborates the content of these relations. The extent of semantic overlap between nouns and verbs determines not only whether N test stimuli will facilitate learning but also

whether N & V test stimuli will produce an additional boost in recall. The advantage provided by N & V stimuli with O-related verbs in retrieving objects was not foundwith N & V stimuli containing S-related verbs. This is curious in view of the finding of Rohwer, Shuel! and Levin (1967) that, in general, the presence of the verb with the subject during retrieval enhances learning more than its absence. The fact that S-related verb conditions produced equivalent recall regardless of the nature of the test stimulus can perhaps be attributed to the special relation existing between subject nouns and S-related verbs. Since the likelihood was great that the full N & V test stimulus could and would be reproduced from memory by the learner because of the maximal semantic overlap existing between the two components, syntactic and semantic relations were equally active and functioning in all three test-stimulus conditions. Thus, no basis for a boost in retrieval existed in the S-related verb conditions. The fact that restoration of the noun-verb context during retrieval produces an additional boost in recall (when contrasted to the noun test stimulus) under some conditions but not others necessitates further investigation. Whereas Rohwer, Shuell, and Levin (1967) obtained this effect, Rohwer and Levin (1968) did not. In the latter study, a slight difference appeared for action verb sentences, but recall was equivalent for still verbs. These findings suggest the need for a study which uses a mixed-list design to contrast the relative effects of various test stimuli. Such an arrangement would insure that the learner is not alerted during storage to the specific value of forthcoming test stimuli and so is prevented from focusing upon only parts of the entire sentence. Also, such a design might settle the discrepancy between the present finding that verbs can cue recall as well as nouns and the previous finding by Rohwer and Levin (1968) that verbs are inferior to nouns. If the psycholinguistic explanation enunciated above is correct, verbs should elicit at least as much

VERB FACILITATION OF

recall as subject nouns, since presumably they lie closer to object nouns in memory storage than do subjects. An alternative interpretation for the finding of additional facilitation resulting from the presence of O-related verbs during recall can be identified. Since transitional probabilities between O-related verbs and their object nouns were moderately high, it is possible that learners guessed the correct nouns during the test trial. However, suspicions that guessing rather than learning facility served to enhance recall scores can perhaps be dispelled by the following arguments. If pure guessing accounts for the results, then this situation should be comparable to a condition where verbs accompany nouns only on the test trial, not on the study trial. Such a condition was examined by Rohwer, Shuell, and Levin (1967), who found that when appropriate verbs were introduced during the retrieval phase, recall was suppressed, even below that of the controls. Thus, performance was inhibited in this situation, not stimulated. Also, if guessing were operating, then the occurrence of many intrusions would be expected. However, in the present study, extralist intrusions were relatively rare, as is commonly found in verbal learning studies. Learners adopt response sets which inhibit the recall of items which have not been previously presented in the test situation, and this set acts to suppress intrusions and guessing. Thus, interpretation of the results of this experiment in terms of a guessing strategy appears to be inadequate since its occurrence is unlikely. However, future research should guard against this possibility by avoiding verb-object combinations with high transitional probabilities. The fact that the S-related verb was able to facilitate learning at all suggests that the verb has a very powerful effect. Even when its semantic overlap with the object noun was minimal, as in the sentence, "The chicken pecks the cigar," the verb was able to enhance recall of the noun. The function which the verb serves, that of arousing relations between

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the two nouns, appears to occur even when the content of the relation is unusual and improbable. This finding thus enhances confidence in the form-class effect as occurring for reasons other than those involving contextual constraint or previously learned connections. Results with the O-related verb indicate that these factors may produce additional enhancement of recall when allowed to operate during retrieval, but, as previous research has shown (Rohwer & Lynch, 1966), constraint does not account for the basic effect of the verb on learning. The finding that the factor of verb construction was unrelated to differential recall of object nouns has implications for alternative interpretations of verb facilitation processes. The first of these, the unit hypothesis, predicted that required learning time would increase when more units were added to the stimulus. The finding in this study that the addition of a preposition which lengthened sentences produced no impairment of learning challenges this hypothesis. It. also challenges the phrase-structure complexity hypothesis, which predicted that the addition of a prepositional phrase to the sentence's grammatical structure would increase task difficulty for learners. The expectations of a third formulation, the elaboration hypothesis, were also disappointed. The elaboration hypothesis embraces a paradox which stands between traditional associationistic views of learning and modern empirical findings. The paradox refers to the improvement in learning which results from the addition of special kinds of units to the materials being learned (Rohwer, 1967). That is, the inclusion of m o r e material is associated with better learning. This hypothesis predicted that, since both verb and preposition connectives facilitate the learning of paired nouns, the combination of the two connectives would enhance learning even more owing to the addition of the separate effects of each. However, verb-preposition combinations did not produce better learning than verbs.

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The fact that none of these hypotheses received support suggests that a view of learning based on an additive model is inadequate for selecting variables which will account for the way nouns in sentences are processed, stored, and retrieved. Asch (1968) argues that those aspects of verbal materials important for learning are ones which arouse relations among the components being learned rather than ones which treat the components as independent units summed together. A sentence consists of parts interconnected so as to form a unique whole not reducible without a loss of these relations and thus a loss of meaning. A major portion of the task of arousing relations is performed by verbs, and as discussed previously, two types of relations, syntactic and semantic, can be distinguished. The failure of the verb construction factor to differentially influence recall contrasted to the success of the verb relation factor, supports Blumenthal's (1967) contention that it is the nature of the relations among sentence parts rather than the type of phrase structure segmentation which determines the psychological organization of sentences in memory. In order for verb construction to affect learning, the nature of the specific grammatical relations imposed by verbpreposition connectives must be varied. The present study utilized a heterogeneous collection of two-unit verbs and did not examine the consequences of specific subcategories. In pursuing this line of research, one can find a basis for specifying and manipulating such relations in a recent paper by Fillmore (1968), in which he attributes to verbs and prepositions the function of identifying case relations among nouns in the deep structure of sentences. Not only verbs and prepositions but also pictures can enhance learning by depicting relations among nouns. Rohwer, Lynch, Levin, and Suzuki (1967) found that labeled pictures surpassed printed names, and action pictures were superior to still pictures in producing facilitation. Also, Davidson (1964)

found that the presence or absence of facilitation depended upon whether objects in drawings overlapped or were separated. These findings raise the question of the nature of the underlying relations which are aroused. Perhaps at a deep level, image configurations are involved in the storage of materials being learned, at least those involving concrete objects and actions. The acceptance of an explanatory orientation which speaks of the arousal of relations among parts of a sentence means that attention must be directed towards examining the specific nature of these relations which account for their ability to facilitate learning. The work of transformational grammarians supplies a basis for predicting and describing the nature of some kinds of syntactic and semantic relations. The study of the structure of associations among lexical items may also assist in the understanding of semantic relations aroused when words are combined. It is anticipated that manipulation of variables suggested by these sources will be able to supply empirical findings which will in turn illuminate the psychological processes occurring and accounting for the verbal facilitation of pairedassociate learning.

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1967, 6, 203-206. CHOMSKY,N. Aspects of the theory of syntax. Cambridge, Mass. : M.I.T. Press, 1965. CORER,C. N. On some factors in the organizational characteristics of free recall. American Psychologist, 1965, 20, 261-272. DAVlDSON, R. E. Mediation and ability in pairedassociate learning. Journal of Educational Psychology, 1964,55, 352-356. DEESE,J. The structure of associations in language and thought. Baltimore: The Johns Hopkins Press, 1965.

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FILLMORE,C. J. The case for case. In E. Bach and R. T. Harms (Eds.), Universals in Linguistic Theory. New York: Holt Rinehart & Winston, 1968. Pp. 1-88. JOHNSON, N. F. The psychological reality of phrasestructure rules. Journal of Verbal Learning and Verbal Behavior, 1965, 4, 469-475. KATZ,J. J., & FODOR,J. A. The structure of a semantic theory. In J. A. Fodor & J. J. Katz (Eds.), The structure of language: Readings in the philosophy of language. Englewood Cliffs, N.J.: PrenticeHall, 1964. Pp. 479-518. ROHWm~, W. D., JR. Constraint, syntax and meaning in paired-associate learning. Journal of Verbal Learning and Verbal Behavior, 1966, 5, 541-547. ROHWER,W. D., JR. Social class differences in the role of linguistic structures in paired,associate learning: Elaboration and learning proficiency. Final report of U.S. Office of Education, Bureau of Research, Project Number 5-0605, Contract Number OE-6-10-273, November 1967. ROHWZR, W. D., JR., & LEVlN, J. R. Action, meaning and stimulus selection in paired-associate learning. Journal of Verbal Learning and Verbal Behavior, 1968, 7, 137-141.

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(Received June 27, 1969)