JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR

THE HISTORY OF IMITATION IN LEARNING THEORY:THE LANGUAGE ACQUISITION PROCESS

EFFIE KYMISSIS AND CLAIRE L. POULSON

QUEENS COLLEGE AND THE GRADUATE SCHOOL,CITY UNIVERSITY OF NEW YORK

The concept of imitation has undergone different analyses in the hands of different learning theoriststhroughout the history of psychology. From Thorndike's connectionism to Pavlov's classical condi-tioning, Hull's monistic theory, Mowrer's two-factor theory, and Skinner's operant theory, there havebeen several divergent accounts of the conditions that produce imitation and the conditions underwhich imitation itself may facilitate language acquisition. In tracing the roots of the concept of imitationin the history of learning theory, the authors conclude that generalized imitation, as defined andanalyzed by operant learning theorists, is a sufficiently robust formulation of learned imitation tofacilitate a behavior-analytic account of first-language acquisition.Key wvords: theories of imitation, behavioral history, language, generalized imitation, children

Imitation has been the subject of much sys-tematic investigation in psychology and hasbeen an important concept in the study of thelinguistic development of infants and children(Poulson, Nunes, & Warren, 1989). Over theyears, several divergent accounts of the con-ditions that produce imitation have been pro-posed, creating numerous arguments and con-troversies. There has been disagreement on thecriteria defining imitation, on the processes un-derlying it, and on the conditions under whichimitation facilitates language acquisition. Sometraditional psycholinguists such as Bloom,Hood, and Lightbown (1974), Clark and Clark(1977), Chomsky (1986), and Dale (1976) havenot accepted imitation as sufficient to accountfor language acquisition in children. Never-theless, they may have overlooked the conceptof generalized imitation as presented in thecontext of operant learning theory. General-ized imitation, as defined and investigated byBaer and Sherman (1964), Baer, Peterson, andSherman (1967), and Baer and Deguchi(1985), describes in an orderly way the con-

Support for the preparation of this article was madeavailable by Grant HD 22070 from the National Instituteof Child Health and Human Development and by Re-search Award 667441 from the Professional-Staff Con-gress/City University of New York, Queens College/CUNY. Appreciation is extended to Thom Verhave, Don-ald M. Baer, and Bruce L. Brown for their helpful com-ments during the preparation of this manuscript. Corre-spondence and requests for reprints should be sent to ClaireL. Poulson, Department of Psychology, Queens College/CUNY, Flushing, New York 11367/0904.

ditions under which first-language acquisitionoccurs. A complete description of generalizedimitation is provided in the final section of thispaper.Throughout the history of psychology,

learning theorists have regarded imitation assuch an important construct that virtually allof them have addressed imitation one way oranother. In general, the development of thetheories of imitation has followed the devel-opment of theories of learning, so that the his-tory of imitation reflects in part the history oflearning theory. The purpose of this paper isto trace the roots of the concept of imitationin the history of learning theory and to presentthe logic of a behavior-analytic account of lan-guage acquisition using the concept of gener-alized imitation.

CONNECTIONISMThe starting point of learning theory in the

United States is Edward Thorndike's "con-nectionism." This is the original stimulus-re-sponse-consequence psychology of learningthat has influenced so many psychologists ofthis century and continues to influence muchexperimentation worldwide. According toThorndike, most animal and human learningis due to response-contingent reward in spe-cific stimulus situations. In this form of learn-ing, sensory stimulus impressions are con-nected to responses by "satisfaction" and"discomfort" as consequences, as described inThorndike's (1911) famous law of effect.

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Thorndike believed that the laws of instinct,exercise, and effect were sufficient to explainthe phenomenon of imitation in human andnonhuman behavior. He considered some formsof imitation to be purely instinctive and othersto be only adjuncts to the formation of a habit.Using these two concepts, he described the hu-man imitative process as follows: A child pro-duces a great variety of sounds instinctively.Some of these sounds resemble words and arerewarded by the child's environment. Thus,according to the law of effect, the child learnsto use the rewarded sounds in similar situa-tions to achieve similar results. Thorndike alsoconsidered the possibility that a child may in-stinctively feel satisfaction at producing a soundsimilar to the one that "rings in the ears ofmemory and has meaning" (Thorndike, 191 1,p. 253). This type of satisfaction, Thorndikethought, is like the instinctive satisfaction ex-perienced by someone who creates an objectresembling some familiar and meaningful ob-ject in the person's world.

Even though Thorndike considered imita-tion to be of value in human learning, he as-signed it less value in nonhuman learning. Al-though he recognized the fact that some birdsimitate word-like sounds, he considered thisphenomenon to be only a peculiarity of thespecies, an indirect result of an instinctive acthaving nothing to do with learning. Thorndikethought this phenomenon should be regardedas different from the phenomenon of imitationin humans.

Nevertheless, Thorndike recognized thatsome nonhumans act in many ways that ap-pear to be truly imitative. For example, manyyoung birds appear to lose the fear of telegraphwires or railroad trains soon after hatchingand subsequently acquire habits of feeding oncertain plants and in specific places, like theirmothers. Most young nonhumans behave liketheir mothers, but Thorndike believed that thisonly represents a pseudoimitative phenomenonresulting from some instinct. Thorndike failedto demonstrate learning by imitation in non-humans. His typical experiment with dogs,cats, and monkeys was to place 2 subjects insimilar cages, one next to the other. One ofthe subjects was trained to get out of the cage,and the other was untrained. Although theuntrained subject watched the trained subject'smotions of getting out of the cage many times,the untrained subject failed to learn the trick.

Thorndike reasoned that there is no proof thatnonhumans imitate muscular acts of othernonhumans, and he believed that those actsthat appear to be imitative only simulate im-itation (Thorndike, 191 1). Thorndike was fullyaware of the fact that his views contradictedthe testimony of several animal trainers whoclaimed that nonhumans do learn by imitation,but he insisted on his view because he couldnot explain this phenomenon. According to thelaw of effect, the only way to learn is by doingand then experiencing satisfaction. Because thephenomenon of secondary reinforcement(Skinner, 1938) or symbolic reward was notfamiliar to Thorndike, a complete explanationof imitation in terms of the law of effect wasnot possible.

Thorndike was not the only turn-of-the-century theorist who regarded imitation as aninstinctive act. At that time, the concept ofinstinct was so popular that it was used toexplain many phenomena that are now ana-lyzed in terms of other learning processes. Asa result, several psychologists of the late 19thand early 20th centuries thought imitation tobe innate. Some of them, like Thorndike'spredecessor C. L. Morgan (1896), describedtwo forms of imitation in humans and non-humans: "instinctive" and "intelligent," bothbased on innate tendencies. "Instinctive imi-tation ... is an organic response independentof experience; intelligent imitation is due toconscious guidance, the result of experience,and based upon the innate satisfaction whichaccompanies the act of reproductive imitation"(Morgan, 1896, p. 174). John Watson (1919),who attempted unsuccessfully to study imita-tion in infants, recognized that the existinganalysis of the imitative instinct was incom-plete, but he considered Thorndike's view tobe "as accurate as any we have" (Watson,1919, p. 259). Robert Woodworth (1918) alsoagreed with Thorndike in that "imitation ap-pears not to afford a means by which animalslearn" (Woodworth, 1918, p. 184). Neverthe-less, Woodworth recognized that in humansthere is "a natural tendency to try to imitate"(Woodworth, 1918, p. 185), which is impor-tant in the early life of the individual andfacilitates trial-and-error learning. Other the-orists, like Tarde (1895/1903), Ross (1908),and Wissler (1923), emphasized the role of theimitative instinct in the social development ofthe individual. From the point of view of the

IMITATION AND LEARNING THEORY

learning theorists, the main problem with this"nativistic" view of imitation is that, by con-sidering imitation to be instinctive, these in-vestigators retarded further scientific inquiryregarding the learning processes underlyingthe phenomenon.

CLASSICAL CONDITIONINGAs Thorndike was formulating his law of

effect, the reflex was increasingly subjected toexperimental analysis (Sechenov, 1863/1965;Sherrington, 1906). In psychology, reflex wasdefined as "the reliable production of a par-ticular response by a specified stimulus" (Ca-tania, 1984, p. 32). Reflex relations came tobe considered as the fundamental units of be-havior and the basis for understanding com-plex behavioral processes (Skinner, 1938). Allresponses, simple or complex, were regardedas the combination of reflex relations; when-ever the eliciting stimuli of responses were notobvious, appropriate stimuli were hypothe-sized. In addition, all behavior was regardedas a chain of reflexes, because it was assumedthat the elicited response of one reflex couldfunction as the eliciting stimulus of another.

Pavlov's (1927) experimental study of con-ditioned reflexes grew out of the above hy-pothesis concerning the centrality of the re-flexes. In his classic experiment, food powderwas placed in a dog's mouth (unconditionedstimulus) and salivation was produced (un-conditioned reflex). When an arbitrary neutralstimulus was paired repeatedly with the food,it came to produce salivation in its own right(conditioned reflex). The neutral stimulus hadbecome a conditioned stimulus. Although thethree concepts of contiguity, reflex, and con-ditioning were well known to science beforePavlov's experiments, Pavlov conceptualizedthem differently-he was one of the first tostudy the phenomena of conditioned reflexesempirically and to provide the terminology forthem.

George Humphrey was one of the first toexplain imitation as conditioned reflexes. Not-ing that an imitative response resembles thestimulus that produces it (activity of anotherorganism), Humphrey defined imitation as"action involving a conditioned reflex the sec-ondary stimulus of which is similar to the re-action" (Humphrey, 1921, pp. 4-5). In thisway, he used the notion of reflex chains to

explain imitation before this notion becamepopularized by Holt. Humphrey described im-itation as follows: In the case of a crying baby,thc original stimulus may be pain. But oncethe baby starts crying, it produces a responsethat is also an auditory stimulus, that is,thecrying as heard by the baby itself. This sec-ondary auditory stimulus produces another re-sponse, the reaction, which is more crying, andthrough this "circular reaction" more cryingresults in further crying. "Action of this typemay be regarded as the elementary unit ofimitation. It depends upon the fact that manand animals have senses by which they canperceive the reactions to stimuli from the sameor other senses" (Humphrey, 1921, p. 4).

Humphrey's analysis has two serious lim-itations: First, he does not explain how anactivated reflex ever abates. He does mentionthat the reflex disappears when it stops beingsupported by the primary stimulus, but he doesnot explain how that happens. Second, he doesnot explain how infants come to imitate others.He gives only a partial answer to this questionby observing that in cases of human and non-human imitation of others "the original sec-ondary stimulus comes from without" (Hum-phrey, 1921, p. 5), meaning outside of thebody.

Humphrey's problems were encountered byall the theorists who tried to explain the phe-nomenon of imitation using the Pavlovian con-ditioning model. Theorists who took such anassociationist stand are many, but four of themare especially worth mentioning. AlexanderBain (1855) was one of the first theorists whorejected the notion, long before Thorndike'sand Pavlov's time, that imitative behavior isinstinctive. Bain also made some very impor-tant observations that are consistent with laterinterpretations of imitation as a learned re-sponse. Bain held that imitative behavior doesnot appear very early in life, that it developsslowly, and that young children imitate adultsmuch less than adults imitate young children.Bain used a simple associationist view and triedto explain the phenomenon of imitation as arepetition of connections of stimuli and re-sponses. These connections are based on some"coincidence between a movement and the ap-pearance of that movement in another person"(Bain, 1855, p. 408). The main problem withBain's position, which was also a problem forthe Pavlovian explanation of the phenomenon,

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was that it could not explain why some as-sociations lead to imitation and some do not.

Like Humphrey, Floyd Allport (1924) alsorejected the idea of an instinctive drive to im-itate. He believed that "some acts of allegedinstinctive imitation are to be explained as con-ditioned circular responses" (Allport, 1924, p.240). When children hear themselves talk, theyestablish ear-vocal reflexes by associating theauditory and the speech centers, as in the fol-lowing example:

Chance articulation of the syllable da causesthe baby to hear himself say it. The auditoryimpulse is conveyed to the brain centerswhere it discharges into the efferent neuronsto muscle groups used in pronouncing thesame syllable. An ear-vocal habit for da isthus established. (Allport, 1924, p. 184)

Thus, when children perceive speech, the ef-fect of that speech is merely to invoke alreadyestablished reflexes, such that the perceivedspeech is not imitated but only repeated. All-port thus used the idea of the circular associ-ative mechanism with special emphasis on therole of social stimuli in eliciting imitation.

Another investigator who rejected the ideaof a native imitative tendency and adopted anassociationist position was John Dashiell(1928). Dashiell identified and described twotypes of imitation: habitual and intentional im-itation. Habitual imitation is "some sort oflearned reaction, learned by the process of at-taching the response (not in itself a new one)to the sound or sight of another person so act-ing" (Dashiell, 1928, p. 434). This type ofimitation was later termed by Miller and Dol-lard (1947) "matched-dependent behavior."Intentional imitation is "the intentional copy-ing of word, deed, or feeling" (Dashiell, 1928,p. 434), a process that was later termed byMiller and Dollard (1947) "copying." Al-though Dashiell described these two types ofimitation, he did not identify the specific con-ditions under which each one of them takesplace.

Special attention should be given to EdwinHolt (1931), whose theory of imitation hasinfluenced a great number of social psychol-ogists. Holt differentiated between imitation(responding to another person's stimulus) anditeration (responding to one's own stimula-tion). He held a purely associationist positionand used his "reflex-circle" theory to explain

the two phenomena as follows: Nervous ex-citations from the central nervous system ac-tivate the motor neurons of the muscles re-sponsible for producing a certain sound. Thenervous excitations are random, and the soundthat is made is a random response. This sound,by stimulating the child's auditory receptors,sends an excitation through the auditory nervesto the central nervous system. The incomingexcitation becomes associated with the above-mentioned random nervous excitation, becauseit arrives only a second or two after it in thecentral nervous system. Thus, through asso-ciation by contiguity, the incoming excitationwill restimulate exactly the same motor neu-rons of the muscles that produced the above-mentioned sound, and the muscles will pro-duce the same sound again. After this processis repeated a few times, the impulses elicitedby this sound in the ears will form a synapticconnection with the nerves going to the musclesthat produced the particular sound. Thus, areflex circle will be formed, and the infant willrepeatedly produce any sound that stimulatesits hearing. When this process is well estab-lished, the infant will also repeat similar soundsproduced by other persons. Although Holt'stheory explained how a child comes to imitateothers, the theory did not explain how iterationever ceases. He admitted that a satisfactoryanswer to this question had not been found.

Miller and Dollard (1947) commented ontwo additional points in Holt's theory. One ofthem was that, according to the associationistview, a child should cry harder upon hearingitself cry. The child should also cry harderupon hearing other children cry. Repeated ca-sual observations do not support these conclu-sions. Holt's theory also assumed that the meretemporal contiguity between an auditory stim-ulus and a vocal response is sufficient tostrengthen a connection between them. ButMiller and Dollard asserted that this assump-tion is not correct. They hold, as did Thorn-dike, and later, Skinner, that the strengtheningof the connection depends also upon reward,and that without it, extinction will take place.

HULL'S MONISTIC THEORYAs experimentation in learning theory pro-

gressed, it became apparent that both Thorn-dike's and Pavlov's approaches were seriouslylimited in their account of many learning phe-

IMITATION AND LEARNING THEORY

nomena. Pavlov's theory could not explain thefact that some conditioned reflexes were verydifferent from the unconditioned reflexes withwhich they were paired. Thorndike's theorycould not explain any kind of learning thatoccurred without the organism's performingthe actual response and experiencing satisfac-tion. But in the 1 930s and 1 940s, psychologistscame to believe that both theories might becorrect, each explaining different learning pro-cesses and complementing each other, in theoriginal two-factor theory of learning. Ac-cording to this theory, the two different kindsof learning, conditioning and habit formation,taken together could account for all learnedbehavior (Mowrer, 1960a). Thus, by the mid-20th century, psychological thinking was mov-ing toward an integration of the two ap-proaches. One investigator who attempted thissynthesis to create a monistic theory of learningwas Clark Hull (1943).

Hull was interested in formulating a singletheory of learning that could explain the be-havior of organisms. His theory formally ac-knowledged the importance of historical vari-ables, such as a training history in similarsituations, and deprivational variables, such asbiological need-states. Hull believed that theway these variables influence the organism'sresponding could be summarized by hypo-thetical constructs such as drives and habits,which could be inferred from the organism'shistory or behavior.

There were two main sources of influencethat affected Hull's position. One of them wasPavlov's theory of conditioned reflexes, and theother was Thorndike's revision of the law ofeffect, supported by the phenomenon of thespread of effect, which came about as follows:After a series of experiments, Thorndike cameto discard the idea that reward and punish-ment have equal and opposite effects, as hehad thought originally. He concluded thatpunishment does not weaken stimulus-re-sponse (S-R) connections, but may, in fact,strengthen them. Nevertheless, he observed thatreward strengthens S-R connections more sothan punishment does. Furthermore, experi-mental evidence suggested that rewardstrengthens not only the connection that it tem-porally follows but also adjacent connections.Thorndike held that the effect of reward di-minishes as the unrewarded connections aretemporally removed from the rewarded con-

nection. Even punished connections can bestrengthened to the extent that they are tem-porally proximate to the rewarded connection.Under the influence of the above theoretical

formulations of Pavlov and Thorndike, Hullconsidered the possibility that all forms oflearning may be due to a single source of re-inforcement, namely drive reduction, and thatboth conditioning and trial-and-error learningmay be explained by only one set of assump-tions. His reasoning was as follows: When anorganism emits a response to terminate a drive,such as the one provided by an electric shock,the animal receives reinforcement through drivereduction, and the connections between thedrive stimulus and the response are strength-ened. The same reinforcement can alsostrengthen the connections between the re-sponse and other stimuli, such as the sound ofa buzzer, that might be present during thereduction of the drive. When these connectionsget strong enough to cause drive reduction tothe sound of the buzzer alone and in advanceof the shock, "conditioning" is said to havetaken place (Hull, 1943).

Hull's attempted synthesis of conditioningand trial-and-error learning was applied byMiller and Dollard (1947) to the formulationof their well-known imitation theory. Accord-ing to Miller and Dollard, four fundamentalfactors are involved in the learning process:drive, response, cue, and reward. Their rela-tionship can be summarized as follows: Anorganism emits a response in the presence ofcues in order to reduce a drive. If the responseis not rewarded by a drive-reducing event, itdrops out, and other responses appear. If theresponse is followed by a drive-reducing event,it is rewarded, and the connection between thisresponse and cues that are present is strength-ened. "This strengthening of the cue-responseconnection is the essence of learning" (Miller& Dollard, 1947, p. 17). Miller and Dollardused their drive-cue-response-reward para-digm to explain the phenomenon of imitation.They held that imitation could be subsumedunder three different "submechanisms": samebehavior, matched-dependent behavior, andcopying (Miller & Dollard, 1947, p. 91).The characteristic element of the same be-

havior is that "two people perform the sameact in response to independent stimulation bythe same cue, each having learned by himselfto make the response" (Miller & Dollard, 1947,

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p. 92). For example, two people may enter thesame door because of the sign above it reading"enter." "Same behavior may be learned withor without imitative aids" (Miller & Dollard,1947, p. 92).The second submechanism of imitation,

matched-dependent behavior, occurs wheneverthere is a leader who responds to the environ-mental cues for rewards and an imitator whoseresponses are evoked by cues from the leader'sbehavior. An example of matched-dependentbehavior may illustrate how this submechan-ism of imitation works: Two children, Jim andBobby, were playing at home in the evening.While playing, Jim, the older child, heard thesound of their father's footsteps on the stairs.Bobby, the younger child, did not attend to thisimportant cue. Jim ran to the kitchen to bethere when the father (who usually broughtcandy) came in through the back door. Bobbyhappened at that time to run behind Jim. WhenBobby got to the kitchen, Jim got his candyand so did Bobby. As a result of being re-warded, Bobby ran more often at the sight ofhis brother running, and often he receivedcandy. Eventually, Bobby ran when Jim ran,but Bobby never learned to respond to the cuesto which Jim responded. Miller and Dollardhold that some conditions of social life providerewards for the learning of matched-depen-dent behavior, and they conclude that

In social life, individuals are constantly be-ing placed in situations analogous to the oneabove. The young, the stupid, the subordi-nate, and the unskilled must depend on theolder, the brighter, the superordinate, andthe skilled to read cues which they cannotthemselves discriminate. They can respondonly in the wake of those better instructed.Society, as will be shown, is so organizedthat the situation diagrammed above occursover and over again. (p. 97)According to Miller and Dollard, copying,

the third submechanism of imitation, is a morecomplicated process than matched-dependentbehavior. Copying occurs whenever there is acopier and a model, who also serves as a critic,punishing or rewarding the copier for unsuc-cessful or successful matching of a response."It is crucial that the copier know when hisbehavior is the same; ... in the end the copiermust be able to respond independently to thecues of sameness and difference" (Miller &

Dollard, 1947, p. 92). Miller and Dollard'sanalysis of the task of learning to sing illus-trated the process of copying, with the teacheracting as a singing model and the copier at-tempting to match the notes. In their example,first the model produced a note, whose pitchprovided a cue for the copier to join in withhis or her own note, thus producing additionalimportant cues for the copying process. Thecopier could not respond to the cues of same-ness or difference in the pitch of these twonotes; therefore, the copier in the course oflearning proceeded to produce notes similar inpitch to those of the model in a trial-and-errorfashion. Only the model, who also acted as acritic, could respond to the cues produced bythe notes differentially, and said "yes" whenthe two notes were of the same pitch and "no"when there was a difference between them.The critic's "no" and the internal state of anx-iety that it produced in the copier acted as adrive and as a cue to the copier to vary theresponse in a random manner, until the rangeof trial and error was limited to the correctnote, to which the critic said "yes."

As discrimination was improved, so that thecopier was almost certain to react to the cuesindicating difference with responses pro-ducing acquired drive, and to the cues in-dicating sameness with responses producingacquired reward, the copier became able topractice trial-and-error matching withoutaid from the critic. This may be expressedin abbreviated form by saying the copiercould become his own critic. (Miller & Dol-lard, 1947, p. 157)

Miller and Dollard (1947) compare copyingwith matched-dependent behavior as follows:

In both cases, the responses are connectedto a cue from an independent subject ormodel. In both, likewise, the punishment ofnon-matched responses and the reward ofmatched responses eventually result in con-formity of behavior between the leader andthe follower. The essential difference be-tween the two processes is that in matched-dependent behavior the imitator respondsonly to the cue from the leader, while incopying he responds also to cues of samenessand difference produced by stimulation fromhis own and the model's responses. (p. 159)

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Although copying appears to be a more mean-ingful submechanism of imitation thanmatched-dependent behavior, copying is, nev-ertheless, dependent upon a critic, internal orotherwise, who says "yes" or "no." Subse-quently, the copier is reinforced by the internalstates that "yes" or "no" creates. This followsan instrumental paradigm with no appeal tosecondary reinforcement.Many investigators have criticized the

Miller-Dollard (1947) analysis of imitation.They claim that Miller and Dollard did notstudy imitation, but only discrimination, dur-ing which the so-called imitator responded tocues from the behavior of others (Mowrer,1960b). Furthermore, the Miller-Dollardanalysis of imitation may have accounted foracquisition of some isolated vocabulary in chil-dren, but it did not explain adequately the fullprocess of language acquisition from babblingto use of complete sentences.

It is interesting to note that Miller and Dol-lard (1947) discuss the concept of secondaryreinforcement, introduced by Skinner (1938)and others (see Keller & Schoenfeld, 1950).In fact, Miller and Dollard considered the pos-sibility that the voices of an infant's caregiversmay acquire reward value that in turn helpsreinforce infant babbling. Nevertheless, Millerand Dollard only mentioned this possibilitybut did not elaborate on it, choosing rather toconcentrate on the drive-cue-response-rewardparadigm in which the Thorndikian notion oftrial-and-error learning was incorporated, andto make that the focal paradigm to describeimitation in the social learning of the individ-ual. It was 0. Hobart Mowrer (1960a, 1960b)who incorporated the phenomenon of second-ary reinforcement in his autistic theory of im-itation and offered a more satisfactory accountof nonhuman and human word learning.

TWO-FACTOR THEORYAs experimentation in learning theory con-

tinued, several problems were identified inHull's monistic theory of learning (Mowrer,1960a), one of them being the fact that Hull'stheory synthesized the Pavlovian and Thorn-dikian forms of learning only when the re-sponse to the conditioned stimulus was the sameas the response to the unconditioned stimulus.But often it was shown that the two responsesmay be radically different, for example, an

organism's unconditioned response may berunning, but its conditioned response may bejumping. Furthermore, it was becoming ap-parent that although the original two-factortheory had an advantage over the Pavlovianand Thorndikian views considered separately,it could not account for some important learn-ing phenomena, one of those being the phe-nomenon of avoidance learning (Mowrer,1960a).To offer an alternative explanation of avoid-

ance learning, Mowrer formulated the secondversion of two-factor theory by taking into ac-count the phenomenon of fear conditioning.Consider a typical experiment in which a ratis placed in a long narrow box consisting oftwo compartments, one of them black and theother white. Suppose that the rat receives shockonly in the white compartment, and alwaysafter the sound of a buzzer. After exploringthe box, if the rat stays in the white compart-ment and receives a shock, it will escape byrunning into the black compartment. If weremove the rat from the black compartmentand place it back in the white compartmentand produce the sound of the buzzer, the ratwill not wait for the shock. It will avoid theshock by running into the black compartmentimmediately. This behavior has been calledavoidance learning. According to Mowrer(1 960a), in the avoidance learning experimentthe rat learns (a) to be afraid of the sound ofthe buzzer in the white compartment and (b)to reduce the fear, and avoid the shock whenit is presented, by running into the black com-partment. First, fear operates as an interven-ing variable and gets attached to neutral stim-uli through conditioning, inducing a secondarydrive. Then, fear motivates the subject to per-form an instrumental act to reduce the drive.Mowrer termed the former type of learningsign learning, and the latter, solution learning.He believed that sign learning involved thesmooth muscles and produced involuntary re-sponses (emotions), whereas solution learninginvolved the skeletal muscles and produced vol-untary responses (behavior).

Later, Mowrer's second version of the two-factor theory of learning was revised by Mow-rer himself to offer a satisfactory account ofthe phenomenon of secondary reinforcement,and at the same time to "provide the basis fora new and superior theory of habit" (Mowrer,1960b, p. 7). Mowrer, in his revised version

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of two-factor theory, considered a fact that wasalready known to learning theory, namely thata first-order conditioned stimulus can act as asecondary reinforcer, not only to produce higherorder conditioning but also to produce newhabits. For example, if an organism is taughtto salivate upon the occurrence of a salientstimulus, the subject, if given the opportunity,will emit a response that will produce the sa-lient stimulus. In other words, the subject willlearn to perform a response, not to receivereward but to receive the sign or the promiseof the reward. The term drive has been usedto describe this tendency to emit a certain re-sponse in the presence of a certain need. Ac-cording to Mowrer, behavior consists of twokinds of approach and two kinds of avoidancetendencies:

If an independent stimulus arouses fear, flightis likely to follow; whereas response-corre-lated stimuli which arouse fear produce in-hibition. And if an independent stimulusarouses hope, approach will occur; whereasresponse-correlated stimuli which arousehope produce response facilitation or "habit."(Mowrer, 1960b, p. 10)

Thus, the new version of Mowrer's revisedtwo-factor theory considers all learning to besign learning, with solution learning as its de-rivative, and the theory assumes two kinds ofreinforcement: drive decrement (reward) anddrive increment (punishment).Mowrer applied this new version of two-

factor theory to first-language learning andoffered a new theory of language acquisition,which came to be known as the "autism" orthe "autistic" theory of imitation (Mowrer,1960b). According to this theory, for an or-ganism to learn to produce a particular sound,the sound has to be heard repeatedly, in as-sociation with a form of decremental reinforce-ment. For example, in the case of the humaninfant, the caregiver's voice is likely to be pairedwith food, warmth, and comfort. In this way,the sound takes on secondary reinforcementproperties, so that when the infant hears itselfmake the sound (or an approximation of it)the infant will be automatically reinforced,and the probability increases that the infantwill repeat the sound. "Imitation, as thus in-terpreted, becomes a sort of automatic trial-and-error process, one that is dependent uponreward from another organism, or 'parent per-

son,' only in an indirect, derived sense" (Mow-rer, 1960b, p. 73). Thus, the main differencebetween Mowrer's autistic theory and Thorn-dike's trial-and-error theory of imitation is that,according to Mowrer, the organism acquiresthe habit of producing a sound not by makingit and then experiencing satisfaction, but byexperiencing satisfaction while hearing it be-ing made.

Mowrer's own major criticism of the autistictheory of language learning has been its ina-bility to account for children's use of negativewords that have not been paired with the"good" things in life. To explain the phenom-enon, Mowrer recognized the fact that childrenuse positive and negative words in an instru-mental fashion to receive reinforcement that isno longer autistic in nature. Thus, Mowrerrecognized the significance of the instrumentaluse of language, but only after the languagehas been well established on an autistic basis(Mowrer, 1960b).

OPERANT CONDITIONINGA radical departure from the traditional S-

R psychology began in the 1930s with the ex-perimental work of B. F. Skinner, who rejectedthe use of hypothetical constructs and pursueda behavioristic philosophy of science. Skinner(1938) differed in his approach from the ex-isting S-R psychology, which assumed that thereflex was the appropriate model for all be-havior. Instead, Skinner distinguished be-tween two kinds of responses, respondents,which are elicited, and operants, which areemitted. Although respondents are triggeredby known eliciting stimuli, operants are notassociated with any such eliciting stimuli. Anoperant may be associated with an antecedentstimulus situation only in the sense that thestimulus may set the occasion for the operantresponse to occur. In such a case, the operantresponse is called a discriminated operant, andthe stimulus is called a discriminative stimulus.A discriminative stimulus and a discriminatedoperant may occur together in time, but Skin-ner did not view them as forming an S-Rconnection. In fact, the power of the discrim-inative stimulus is derived entirely from itsassociation with contingencies of reinforce-ment. Thus, Skinner called attention to thetype of conditioning in which reinforcement isassociated with the response, rather than with

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any stimulus producing the response. He calledthis type of conditioning operant conditioning.Reinforcement as a process names a relationbetween response and environment.

The relation is complex and must includeat least three components. First, a responsemust have some consequence. Second, theresponse must increase in probability....Third, the increase in probability must occurbecause the response has this consequence,and not for some other reason. (Catania,1984, p. 64)Skinner argued that we can understand

complex behavior in terms of two kinds oflearning: stimulus discrimination and responsedifferentiation. Stimulus discrimination is thetype of learning that allows the organism torespond differentially in the presence of oneor more stimuli called discriminative stimuli.Response differentiation is the type of learningthat changes the organism's way of respondingaccording to changes in the criterion of rein-forcement. Thus, differential reinforcement ofcertain forms of responding can "shape" theorganism's behavior. Stimulus discriminationand response differentiation permit the for-mation of response chains in which the re-sponse of one segment becomes a discrimina-tive stimulus for the response of the nextsegment. Thus, Skinner analyzed behavior ingeneral, as well as verbal behavior (Skinner,1957) in particular, in terms of operant con-ditioning principles.

In his analysis of verbal behavior, Skinner(1957) emphasized the function of verbal re-sponding. According to this analysis, verbalbehavior is maintained by environmental con-tingencies, whose schedule remains relativelyconstant in a given cultural environment. Ac-cording to Skinner, languages, as studied bylinguists, are "the reinforcing practices of ver-bal communities" (Skinner, 1957, p. 461). Ac-cording to Skinner, a functional analysis ofverbal behavior can account for the origin ofa verbal environment if a response "associatedwith a state of deprivation is an importantstimulus for a 'listener' who is disposed toreinforce the 'speaker' with respect to that stateof deprivation" (Skinner, 1957, p. 464). In thisway Skinner was able to explain how a hungryhuman infant's reflexive crying can become anoperant response shaped by the caregiver'spresentation of appetitive stimuli and removal

of noxious stimuli contingently upon the in-fant's vocal behavior. Skinner's analysis of lan-guage acquisition focuses primarily on the re-inforcing practices of the larger culturalenvironment and the maintenance of speech inadults. Behavioral developmental psycholo-gists focused the principles set forth by Skinnerto address more directly the acquisition of adult-like sounds by human infants.

Specifically, Sidney W. Bijou and DonaldM. Baer (1961, 1965, 1978) wrote the firstdevelopmental textbooks to use Skinner's be-havior analysis approach to a learning theoryof infant and child development. Bijou andBaer defined psychological development as"progressions in interactions between behaviorand environmental events" (Bijou & Baer,1961, p. 14). They defined verbal behavior as"that class of vocal behavior that is reinforcedthrough the action of another person" (Bijou& Baer, 1965, p. 159), thus emphasizing therole of interactions of responses and stimuli inthe infant's language acquisition process. Baer'sstudent, Todd R. Risley (1966, 1977), follow-ing the behavioral developmental psychologytradition, combined operant conditioning ele-ments with Mowrer's autistic theory of imi-tation and offered the most detailed operantmodel of first-language acquisition.To reiterate, according to Mowrer's autistic

theory of imitation, parental verbal stimuli be-come conditioned reinforcers by being associ-ated with the "good things" in the infant's life.In turn, some of the infant's vocalizations, thoseapproximating the parental sounds, are dif-ferentially reinforced by the stimuli they pro-duce. The more similar the infant's soundsbecome to the parental sounds, the more re-inforcing they become. Risley (1966, 1977),analyzing Mowrer's theory from an operantconditioning point of view, identified the fol-lowing three problems.

First, Risley argued that mere pairing of areinforcer with a stimulus is not sufficient tomake the stimulus a conditioned reinforcer. Heargued that a stimulus becomes a conditionedreinforcer only when it becomes a discrimi-native stimulus for a response to be reinforced.Because, in the natural environment, parentalreinforcement of infant vocalizations does notappear to be contingent upon specific vocalresponding, parental vocal responding is notlikely to become discriminative for infant re-sponding. Thus, parental vocalizations are un-

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likely to become strong conditioned reinforc-ers. In fact, Risley need not have put forth thisargument at all, because subsequent review ofthe conditioned-reinforcement literature in-dicates that it is not, indeed, necessary to dem-onstrate discriminative control by stimuli tolabel them conditioned reinforcers (e.g., Fan-tino, 1977). Nevertheless, it is the case thatconditioned reinforcers are potentially weakerthan primary reinforcers to the extent that theirstrength depends on their being paired withprimary reinforcers. Thus, Risley's point thatparental vocalizations may be relatively weakreinforcers is undisputed.

Second, Risley argued, even in the case inwhich parental vocal sounds acquire secondaryreinforcement properties, the infant shouldproduce these sounds with greater probabilitywhen the infant is in a state of deprivation.Nevertheless, observation shows that infantsbabble more when they are fed, dry, and con-tent rather than deprived (e.g., Lewis, 1959).A third problem with Mowrer's autistic the-

ory of imitation, according to Risley, is thatspectrographs indicate that parental sounds aredifferent from infant sounds (e.g., Lenneberg,1964). This difference would be expected toweaken the reinforcing properties of parentalsounds considerably.

Thus, Risley's arguments suggest that in-fant vocalizations that approximate parentalvocalizations may have only weak conditioned-reinforcement properties. More powerful re-inforcement contingencies may be required tosupport an operant conditioning account of ini-tial-language acquisition. What is needed forthis account, according to Risley, is that someongoing level of reinforcement from the in-fant's caregivers be made contingent on somelevel of infant vocalization. Only when the in-fant's operant level of vocalizations is suffi-ciently high will the weak conditioned rein-forcers resulting from the infant's "autisticimitation" be able to increase the probabilityof adult-like sounds in the infant. In this anal-ysis, Risley sees the parent as playing a moreactive role in the infant's language acquisitionprocess than Mowrer did. According to Mow-rer, all the parents have to do to produce lan-guage is talk while caring for their infants.According to Risley, in addition to talking whilecaring for their infants, parents must also pro-vide direct contingencies for their infant's vocalbehavior.

As a detail of Risley's first argument above,Risley states that parental reinforcement ofinfant vocalizations does not appear to be con-tingent upon specific vocalizations in the nat-ural environment. Whereas his statement wastrue at the time, it should be noted that sub-sequent research and reanalysis of data (e.g.,Moerk, 1983) suggest that parents may, in-deed, present antecedentsand consequences dif-ferentially with respect to the form and contentof infant utterances. This new information doesnot weaken the force of Risley's main argu-ments, however, and, in fact, strengthens hisoverall position on the acquisition of language.Risley contributed two main points with hisarguments: (a) that under certain conditions aweak conditioned reinforcer (similarity be-tween parent and infant vocalizations) couldhave an important function in first-languageacquisition, and (b) that those certain condi-tions (some level of direct parental reinforce-ment for infant vocalization) were likely toobtain in the natural environment. The newresearch merely buttresses Risley's latter point.

Another theorist, Fry (1966), emphasizedthe active role of the parent in the process ofimitation even more than did Risley. Fry's de-scription of the development of the phonolog-ical system is remarkably consistent with thatof the operant model, with respect to the roleof imitation in the process of first-languageacquisition. According to Fry, during the bab-bling stage the infant learns to associate dif-ferent kinds of speech sounds with the actionof the articulatory organs that produce thosesounds, and the infant practices the reproduc-tion of the same sounds by repeating the samemovements over and over. After the establish-ment of this feedback mechanism, the infantgains control over his speech activity and learnsnew sounds and modifies old sounds throughimitation. Imitation "is here taken to meansimply that the child tries to produce a soundthat strikes him as similar to the sound thathe hears coming in from outside" (Fry, 1966,pp. 190-191). Although Fry is not a learningtheorist, he holds that imitation plays a largerole in the development of speech articulation.According to Fry, the acquisition of speechthrough imitation depends upon the parents'frequent presentation of vocal models and re-inforcement. Parents present vocal models totheir infants in appropriate contexts, and theinfant's attempt to approximate the model is

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usually followed by praise and repetition ofthe correct vocal model by the parent. Underthese circumstances the infant should producesuccessively closer approximations to the model,eventually imitating the parent successfully.Gradually, the context will replace the adultmodel as the discriminative stimulus for theappropriate vocalizations. Thus, in his anal-ysis Fry emphasizes the function of what Ris-ley (1966, 1977) labels "discriminated imita-tion," during which the imitator is reinforcedby an external agent for imitative respondingonly in the presence of a narrow range of dis-criminative stimuli.

Fry's discriminated imitation approach maybe contrasted to Baer's generalized imitationapproach, which focuses on the formation ofa response class of imitation maintained by aconditioned reinforcer, the conditioned rein-forcer being the class of stimulus similaritiesbetween the model's response-produced stim-uli and the imitator's response (Baer & De-guchi, 1985; Baer et al., 1967; Baer & Sher-man, 1964).

Baer and Sherman (1964) were among thefirst investigators to propose that similarity be-tween the model's behavior and the observer'sbehavior may be the functional variable in pro-ducing the observer's imitative responding. Intheir experiment, Baer and Sherman used so-cial reinforcement from a talking puppet toestablish imitative mouthing, head nodding,and nonsense verbalizations in normal youngchildren. As imitative responding of these threeresponses increased in strength, imitative re-sponding of a fourth response (bar pressing)also increased in strength, even though thatfourth response was never reinforced. Whenextinction of the three previously reinforcedimitative responses was effected with 2 chil-dren, the bar-pressing response was also ex-tinguished. When nonmodeling conditions wereimplemented with 2 other children, the bar-pressing response was extinguished along withthe other responses. When contingent rein-forcement of the three imitative responses wasreintroduced, the bar-pressing response in-creased along with the other three responsesin all 4 children. These findings suggested thatsimilarity between the model's behavior andthe observer's responding may have become areinforcing stimulus dimension of the imita-tor's behavior.Baer et al. (1967) demonstrated generalized

imitation in another experiment in which theytaught 3 nonimitative, developmentally de-layed young children a series of discrimina-tions. In the course of training, the experi-menter presented a series of discriminativestimuli and reinforced the subject's correct im-itative responding. Certain probe imitationswere never reinforced. Nevertheless, never-re-inforced imitative responding increased instrength and remained high as long as rein-forcement of other imitative responding con-tinued. When contingent reinforcement wasdiscontinued for imitative responding duringa differential reinforcement of other-than-im-itating (DRO) phase of the experiment, bothreinforced and nonreinforced imitation de-creased in strength. When contingent rein-forcement was reinstated for imitative re-sponding, both reinforced and nonreinforcedimitation increased in strength. Based on theirresearch, Baer et al. defined generalized imi-tation as follows:Any behavior may be considered imitativeif it temporally follows behavior demon-strated by someone else, called a model, andif its topography is functionally controlledby the topography of the model's behav-ior.... Such control could result, for ex-ample, if topographical similarity to a mod-el's behavior were a reinforcing stimulusdimension for the imitator. (Baer et al., 1967,p. 405)In their analysis of the research on gener-

alized imitation, Baer and Deguchi (1985) de-scribed generalized imitation as a functionalresponse class because of three empirical find-ings. First, some imitative responses that arenever reinforced increase in probability as longas some other imitative responses are rein-forced, and they decrease in probability whenthose other imitations are no longer reinforced.Second, the nonreinforced generalized imita-tive responses persist despite the differentialschedule of reinforcement. Third, the qualityof the nonreinforced generalized imitationscovaries with the quality of the reinforced im-itations. This last point is illustrated in thework done by Lovaas, Berberich, Perloff, andSchaeffer (1966) and Brigham and Sherman(1968). In the Lovaas et al. study, two schizo-phrenic children were reinforced for accu-rately imitating English words. As accuracy ofEnglish-word imitation increased, accuracy of

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never-reinforced Norwegian words increasedas well. The Lovaas et al. study was replicatedby Brigham and Sherman with normal pre-school children, who were also reinforced foraccurately imitating English words. As accu-racy of the English-word imitation increased,accuracy of never-reinforced Russian wordsincreased as well. Nevertheless, Baer and De-guchi did not consider the description of imi-tation as a response class to be an explanationof the phenomenon.

Here, response class is not an explanation;it is only the observation that reinforcementof some members of the class controls theother members in a similar way. Thus, sim-ply describing imitation as a response classdoes not contribute to understanding suchcomplex cases. It is how the response classis molded and maintained that should beexplained. (Baer & Deguchi, 1985, p. 185)Thus, Baer and Deguchi (1985) define im-

itation as generalized imitation and offer aconditioned-reinforcement explanation of thephenomenon, as follows: Once a response classof imitative responding is established throughdirect contingent reinforcement, similarity be-tween the model's output and the observer'soutput becomes a conditioned reinforcer forany new imitative responding. Thus, new im-itative responding is established and main-tained as long as other members of the imi-tative response class are directly reinforced.To provide further empirical evidence for

the above explanation of the phenomenon ofgeneralized imitation, Baer and Deguchi(1985) conducted a series of experiments inwhich children's preference for similarity wasmeasured in a multiresponse apparatus. Theapparatus was a five-paneled table top. Eachpanel contained a light and a push button. Insome trials the middle panel was lit, and inother trials all four side panels were lit. Whenthe middle panel was lit, the child had anopportunity to receive a reinforcer duringbaseline by simply pressing the button andduring intervention by pressing the button andimitating the experimenter. When the sidepanels were lit, the child could choose amongfour different activities by pressing one of thefour buttons and then engaging in its corre-sponding activity. The four possible activitieswere:

1. Observing the experimenter engaged inan activity.

2. Observing the experimenter engaged inan activity, and then imitating the experi-menter.

3. Engaging in an activity different from theexperimenter's.

4. Waiting for the next trial to start.During baseline, the child's preference for

the four activities was measured prior to theintroduction of reinforcement contingent uponimitative responding. During training, thechild's preference for the four activities wasmeasured after being directly reinforced uponimitating the experimenter. It was found thatthe relative frequency of button pressing pro-viding access to nonreinforced imitations in-creased during treatment and remained highas long as other imitative responding was di-rectly reinforced. When reinforcement for thisother imitative responding was discontinued,the relative frequency of button pressing pro-viding access to nonreinforced imitation de-creased to baseline levels. The preference toperform nonreinforced imitation increasedagain when contingent direct reinforcement forother imitative responding was reintroduced.Additional tests indicated that all subjects couldclearly discriminate between responses thatwere to be reinforced and responses that werenot to be reinforced. The authors concludedthat "such clear discrimination weakens anyexplanation relying on difficulty of discrimi-nating between the two classes of imitation"(Baer & Deguchi, 1985, p. 207). Thus, sim-ilarity is isolated as a variable controlling theproduction of generalized imitation.

Additional empirical evidence for the phe-nomenon of generalized imitation was pro-vided by Poulson and Kymissis (1988), whodemonstrated generalized gestural imitation ininfants as young as 10 months of age. Fur-thermore, Poulson, Kymissis, Reeve, Andrea-tos, and Richards (in press) demonstratedgeneralized vocal imitation in infants as youngas 9 months of age. By replacing the experi-menter with a parent, the infants' fullcooperation was ensured and their natural lan-guage learning environment was approxi-mated. The findings of these two studiesstrengthen the operant-learning account oflanguage development, because they demon-strated the phenomenon of generalized imi-tation in children at an age close to the age of12 months, when most children emit their firstwords.Most traditional psycholinguists (Bloom,

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Hood, & Lightbown, 1974; Clark & Clark,1977; Dale, 1976) downplay the role of re-inforcement and imitation in language acqui-sition because observations in the natural en-vironment suggest that children often producenovel linguistic forms such as "throwed." Pre-cisely because such a word is novel it cannothave been modeled for the children to imitate,and because it has never been produced by thechild before, it has never been reinforced. Tra-ditional psycholinguists, therefore, interpretthese novel forms as evidence of internal lin-guistic processes, and they thus dismiss theoperant analysis of the language acquisitionprocess. Nevertheless, the inadequacy of imi-tation to account for first-language acquisitionmay be due to an inadequate definition of im-itation rather than to an inability of learningtheory to account for the linguistic phenomena.Baer and Deguchi's (1985) definition of imi-tation as generalized imitation may be suffi-cient to account for the fact that imitation oftenoccurs in the absence of direct reinforcementor other demand factors in the natural envi-ronment (Baer & Deguchi, 1985). Also, it isconsistent with the observation that childrenproduce many nonreinforced, novel imitativeresponses, as long as they are directly rein-forced for similar imitative responding. Thus,the child who uttered the novel "throwed" mayhave imitated "throw" and been reinforced forits use. The same child may have imitated theuse of the "ed" suffix to form past tense, andthat performance may have been directly re-inforced. Thus, "throwed" would be expectedto occur as a member of a response class con-taining (mostly regular) verbs and past-tensesuffixes such as d, ed, and t, until the childlater learns the exceptions to the rules for reg-ular verbs (Baer, Guess, & Sherman, 1972).

Furthermore, the operant language acqui-sition paradigm is sufficient to account for theprocess of language acquisition as proposed bycurrent linguistic analyses (Dale, 1976). Ac-cording to these analyses, complex speech unitsare not necessarily formed from simpler lin-guistic units combined together. What seemsto be happening in the language acquisitionprocess is that children learn to produce in totomany large linguistic units "working on thepronunciation of sounds, on acquiring words,and on sentence construction simultaneouslythroughout development" (Dale, 1976, p. 195).According to the operant analysis of languageacquisition, the large linguistic units learned

by children may be analyzed as response clas-ses themselves (Risley, 1977). Further exper-imental analysis of the ways in which theseresponse classes are formed should be the focusof a concerted research effort.

Experimental analysis of the conditions gov-erning the formation (and nonformation) ofimitative and other linguistic response classeswould provide a satisfactory account of lan-guage acquisition at the empirical and theo-retical levels for most behavior analysts. It isinteresting to note that such analyses wouldprobably not satisfy the questions of a moretraditional psycholinguist, such as Chomsky,who would be likely to seek a separate mech-anism to further explain the formation of re-sponse classes-perhaps a "response-classacquisition device" of some sort. The meta-physical assumptions of these divergent par-adigms are so different that the same questionsare seldom asked, and even then, the samequestions are seldom satisfied by the same lev-els of explanation. This circumstance has theunfortunate effect of limiting dialogue and in-terest in empirical findings couched in lan-guage that falls outside one's own paradigm.It is to be hoped, nevertheless, that efforts tocommunicate across paradigms will continueto inform both, and that the behavior analyst,although outnumbered by nonbehaviorists, willcontinue to produce orderly descriptions of theconditions governing the formation and non-formation of imitative and linguistic responseclasses.Tracing the concept of imitation in the evo-

lution of learning theory makes it clear thatgeneralized imitation, as defined and analyzedby Baer and Deguchi (1985), may be a suf-ficiently robust formulation of learned imita-tion to facilitate a behavior-analytic accountfor first-language acquisition. First, the the-orists who regarded imitation as an instinctiveact retarded further investigation of imitationas a learned phenomenon. Second, those whoregarded imitation as a conditioned reflex couldnot explain how this reflex ever abates, andwhy some associations lead to imitation andothers don't. Third, Hull's (1943) drive-re-sponse-cue-reward paradigm, as applied toimitation by Miller and Dollard (1947), ledto an analysis of matched-dependent behavior,which has been regarded by operant theoristsas mere discrimination learning and which,therefore, could not account for the generativenature of first-language acquisition. Fourth,

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Mowrer's (1960b) autistic theory of imitationmakes use of the phenomenon of secondaryreinforcement to account for the production ofsounds in human infants. Nevertheless, Mow-rer's theory was unable to account for the in-fant's production of negative words, and it wasfurther found to be inadequate by Risley(1977), who suggested that parents have toplay a more active role in the language ac-quisition process. Both Risley's (1966, 1977)and Fry's (1966) theories emphasized the im-portance of environmental contingencies in theprocess of imitation, but Baer defined andstudied imitation as generalized imitation in away that provided a more satisfactory accountof first-language acquisition using the operant-learning paradigm (Baer & Deguchi, 1985;Baer et al., 1967; Baer & Sherman, 1964).Because generalized imitation can account fornovel linguistic forms such as "comed" or"throwed" as members of a response class basedon past imitation and reinforcement for use ofsimilar but regular verbs, the concept of gen-eralized imitation is powerful. To the extentthat we can experimentally analyze succes-sively larger proportions of children's utter-ances within an operant-learning paradigm, itbecomes less pressing to worry about nonlearn-ing language acquisition paradigms that inprinciple render their subject matter unavail-able for experimentation.

REFERENCES

Allport, F. H. (1924). Social psychology. Boston: Hough-ton Mifflin.

Baer, D. M., & Deguchi, H. (1985). Generalized im-itation from a radical-behavioral viewpoint. In S. Reiss& R. R. Bootzin (Eds.), Theoretical issues in behaviortherapy (pp. 179-217). Orlando, FL: Academic Press.

Baer, D. M., Guess, D., & Sherman, J. A. (1972). Ad-ventures is simplistic grammar. In R. L. Schiefelbusch(Ed.), Language of the mentally retarded (pp. 93-105).Baltimore: University Park Press.

Baer, D. M., Peterson, R. F., & Sherman, J. A. (1967).The development of imitation by reinforcing behavioralsimilarity to a model. Journal of the Experimental Anal-ysis of Behavior, 10, 405-416.

Baer, D. M., & Sherman, J. A. (1964). Reinforcementcontrol of generalized imitation in young children.Journal of Experimental Child Psychology, 1, 37-49.

Bain, A. (1855). The senses and the intellect. London: J.Parker.

Bijou, S. W., & Baer, D. M. (1961). Child development:Vol. 1. A systematic and empirical theory. New York:Appleton-Century-Crofts.

Bijou, S. W., & Baer, D. M. (1965). Child development:

Vol. 2. Universal stage of infancy. New York: Appleton-Century-Crofts.

Bijou, S. W., & Baer, D. M. (1978). Behavior analysisof child development. Englewood Cliffs, NJ: Prentice-Hall.

Bloom, L., Hood, L., & Lightbown, P. (1974). Imitationin language development: If, when, and why. CognitivePsychology, 6, 380-420.

Brigham, T. A., & Sherman, J. A. (1968). An experi-mental analysis of verbal imitation in preschool chil-dren. Journal of Applied Behavior Analysis, 1, 151-158.

Catania, A. C. (1984). Learning (2nd ed.). EnglewoodCliffs, NJ: Prentice-Hall.

Chomsky, N. (1986). Knowledge of language: Its nature,origins, and use. New York: Praeger.

Clark, H. H., & Clark, E. V. (1977). Psychology andlanguage. New York: Harcourt Brace Jovanovich.

Dale, P. S. (1976). Language development: Structure andfunction (2nd ed.). New York: Holt, Rinehart & Win-ston.

Dashiell, J. F. (1928). Fundamentals of objective psy-chology. Boston: Houghton Mifflin.

Fantino, E. (1977). Conditioned reinforcement: Choiceand information. In W. K. Honig & J. E. R. Staddon(Eds.), Handbook of operant behavior (pp. 313-339).Englewood Cliffs, NJ: Prentice-Hall.

Fry, D. B. (1966). The development of the phonologicalsystem in the normal and the deaf child. In F. Smith& G. A. Miller (Eds.), The genesis of language (pp.187-206). Cambridge, MA: M.I.T. Press.

Holt, E. B. (1931). Animal drive and the learning process.New York: H. Holt.

Hull, C. L. (1943). Principles of behavior. New York:Appleton-Century-Crofts.

Humphrey, G. (1921). Imitation and the conditionedreflex. Pedagogical Seminary, 28, 1-21.

Keller, F. S., & Schoenfeld, W. N. (1950). Principles ofpsychology. New York: Appleton-Century-Crofts.

Lenneberg, E. H. (1964). Speech as a motor skill withspecial reference to nonaphasic disorders. Monographsof the Society for Research in Child Development, 29(1,Serial No. 92, The acquisition of language [U. Bellugi& R. Brown, Eds., pp. 115-127]).

Lewis, M. M. (1959). How children learn to speak. NewYork: Basic Books.

Lovaas, 0. I., Berberich, J. P., Perloff, B. F., & Schaeffer,B. (1966). Acquisition of imitative speech by schiz-ophrenic children. Science, 151, 705-707.

Miller, N. E., & Dollard, J. (1947). Social learning andimitation (3rd ed.). New Haven: Yale University Press.

Moerk, E. L. (1983). The mother ofEve. Norwood, NJ:Ablex.

Morgan, C. L. (1896). Habit and instinct. London: E.Arnold.

Mowrer, 0. H. (1960a). Learning theory and behavior.New York: Wiley.

Mowrer, O. H. (1960b). Learning theory and the symbolicprocesses. New York: Wiley.

Pavlov, I. P. (1927). Conditioned reflexes (G. Anrep,Trans.). London: Oxford University Press.

Poulson, C. L., & Kymissis, E. (1988). Generalizedimitation in infants. Journal of Experimental Child Psy-chology, 46, 324-336.

Poulson, C. L., Kymissis, E., Reeve, K., Andreatos, M.,& Richards, L. (in press). Generalized vocal imita-tion in infants. Journal of Experimental Child Psychol-ogy.

IMITATION AND LEARNING THEORY 127

Poulson, C. L., Nunes, L. R. P., & Warren, S. F. (1989).Imitation in infancy: A critical review. In H. W. Reese(Ed.), Advances in child development and behavior (Vol.22, pp. 271-298). San Diego: Academic Press.

Risley, T. R. (1966). The establishment of verbal behaviorin deviant children. Unpublished doctoral dissertation,University of Washington, Seattle.

Risley, T. R. (1977). The development and maintenanceof language: An operant model. In B. C. Etzel, J. M.LeBlanc, & D. M. Baer (Eds.), New developments inbehavioral research (pp. 81-101). Hillsdale, NJ: Erl-baum.

Ross, E. (1908). Social psychology. New York: Macmil-lan.

Sechenov, I. M. (1965). Reflexes of the brain (S. Belsky,Trans.). Cambridge, MA: M.I.T. Press. (Original workpublished 1863)

Sherrington, C. (1906). The integrative action of the ner-vous system. New Haven, CT: Yale University Press.

Skinner, B. F. (1938). The behavior of organisms. NewYork: Appleton-Century.

Skinner, B. F. (1957). Verbal behavior. New York: Ap-pleton-Century-Crofts.

Tarde, G. (1903). The laws of imitation (2nd French ed.,E. C. Parsons, Trans.). New York: H. Holt. (Originalwork published 1895)

Thorndike, E. L. (1911). Animal intelligence. New York:Macmillan.

Watson, J. B. (1919). Psychology from the standpoint ofa behaviorist. Philadelphia: Lippincott.

Wissler, C. (1923). Man and culture. New York: T.Crowell.

Woodworth, R. S. (1918). Dynamic psychology. NewYork: Columbia University Press.