37EUROPEAN JOURNAL OF BEHAVIOR ANALYSIS NUMBER 1 (SUMMER 2002)2002, 11111, 37 - 48

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Two articles in EJOBA (Harzem, 2000a; Ton-neau, 2001) present convincing arguments whichshow that some fundamental changes have to beintroduced in behavior analysis in order to give ita more scientific status. Thus Harzem thinks thatwe should abandon the view that certain typesof overt behavior are evoked by so-called ‘pri-vate events’ or ‘covert-behavior factors,’ since thestatus of these covert entities is far from beingclear. Rather, as materialists, we should assumethat the behavior is evoked by physiological fac-tors:

It is best for conceptual clarity to re-tain the word ‘physiological’ for eventsinside the body, and the word ‘behavior’for actions of the body. For these reasons,it is well to abandon the ‘private event’notion and instead scientifically to focuson behavioral phenomena, including lin-guistic behavior (Harzem 2000a, p. 56).

To be sure, we must deal with the fact thatpeople use, and often quite successfully, so-calledmental terms. But this use does not commit us tothe existence of mental entities; it merely pointsto the problem of giving a correct account ofthe origin and use of these terms. As Harzemsays, the only way to avoid the conclusion thatmental terms refer to mysterious mental entities”is thoroughly to understand how language func-tions” (2000b, p. 130).

In the second article, Tonneau (2001) advo-cates for a reorientation of behavioral researchon the acquisition of verbal behavior. In particu-lar, he shows fundamental shortcomings of theequivalence-class research, which presently domi-nates behavior-analytic research of verbal behav-ior. Moreover, and this is Tonneau’s importantpositive contribution, he points to the crucial rolethat is played by so-called Pavlovian correlationsin a child’s acquisition of verbal behavior. In theselearning events, the child is exposed to the pair-ing of a verbal expression with a nonverbal stimu-lus and the events are the main instrument bywhich young children acquire their vocabulary.

Author’s NoteI am indebted to Max Hocutt and to two anonymous ref-

erees for helpful comments on earlier versions of this paper.Address for correspondence: Nathan Stemmer, 9 Diskin Street,Jerusalem, Israel. Email address: nstemmer@netmedia.net.il

Further Steps Towards an Improved Version of

Behavior Analysis

Nathan StemmerBeth-David Institute, Jerusalem

Harzem (2000a) and Tonneau (2001) maintain that a number of fundamental changes have to be intro-duced in behavior analysis in order to give it a more scientific status. This paper develops in more detail theirsuggestions and analyzes some issues that are necessary for developing an improved version of behavioranalysis. Three main topics are examined. First, various critical features of ostensive learning processes arediscussed, among them the generalizations that are part of the processes, the long-term effect of the learningevents, and the listener behavior that is established in these events. Second, a materialist account is given of theverbal functions of so-called mental terms. This account assumes neither mental nor covert-behavior factors.Finally, the operant processes that establish a child’s initial verbal behavior are examined, and a connection isestablished between these learning processes and the ostensive processes.

Keywords: Verbal behavior, Pavlovian correlations, ostensive learning, mental factors, covert-behaviorfactors, materialism

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These learning processes were indeed analyzedby Skinner (1957, pp. 357-362), but behavioranalysts have largely ignored them, perhaps be-cause they are related to respondent condition-ing. To be sure, as I have argued in Stemmer(1996), children usually begin their very early ver-bal behavior with the help of the operant pro-cesses that establish the controlling function ofso-called action names, action frames, and modi-fiers. (I will come back to this issue later.) But thisdoes not diminish the importance of the role ofPavlovian correlations in the acquisition ofchildren’s initial verbal behavior.

In the present paper, I intend to contribute tothe reorientation of behavior analysis by follow-ing up on the ideas of Harzem and Tonneau. Inparticular, I will analyze in more detail the pro-cesses by which initial verbal behavior is acquired,and I will rely on some of Quine’s conclusions(1960, 1974, 1975) in order to connect the con-clusions of this analysis with Harzem’s request toaccount for the processes by which mental termsare acquired. We will see that such an account canbe given without appealing to mysterious mentalentities or dubious covert-behavior factors. I hopethat the present conclusions will enable us to con-tinue with the reorientation of behavior analysis;a reorientation that will not only give a scientifi-cally more correct character to behavior analysisbut will also make contact with research of otherpsychologists.

Ostensive Learning

Instead of ‘learning by exposure to Pavlov-ian correlations,’ I will use the shorter and morecommon expression ostensive learning (cf. Skinner,1957, p. 360). The following examples will clarifythis notion. Suppose that three-year-old Mary hasnever heard the word ‘giraffe.’ She now goes withher parents to the zoo and, when approachingthe cage of the giraffes, her parents tell her ‘Thisis a giraffe.’ That is, Mary is exposed to the pair-ing of the expression [This is a] ‘giraffe’ with theview of a giraffe. Such an ostensive experience, i.e.,hearing a verbal stimulus while paying attentionto a particular aspect of the environment, or acouple of such experiences, will often transformMary into a competent listener of the word ‘gi-

raffe.’ For example, when Mary afterwards hearsthe command ‘Show me a giraffe,’ she will fre-quently be able to point to a giraffe, if there isone in her environment (see, e.g., Baldwin, 1991;Nelson & Bonvillian, 1978; Ross, Nelson,Wetstone, & Tanouye, 1986; Tomasello & Farrar,1986; Tomasello & Kruger, 1992). And if Maryis already able to transfer listener behavior intospeaker behavior, she might correctly utter ‘gi-raffe’ when being asked ‘What is this?’ while sheis watching a giraffe.

Skinner (1957) also gives an example of lis-tener behavior that is ostensively established. Hedescribes a learning event in which a person isexposed to the ostensive pairing of the verbalstimulus [This is a] ‘Jones-plug’ with a Jones-plug,and he concludes that the “effect upon the lis-tener is … to set up nonverbal behavior in re-sponse to similar stimuli, for example, behavingcorrectly when asked Please hand me a Jones-plug”(p. 360).

Behavior analysts usually explain the learningof words such as ‘giraffe’ by attributing it to thedifferential reinforcement received for emittingthe word in the presence of the correct object.But this account is clearly incomplete, because theprobability that a child, who has never heard theword ‘giraffe,’ will emit the word on a correctoccasion is practically zero. And even if the childhas already heard the word ‘giraffe’ but not on acorrect occasion, the probability that she will emitthe word on such an occasion is still practicallyzero. But such an emission is necessary for theprocess of reinforcement to begin. So what ismissing here? The answer is obvious: The childmust have heard at least once the word ‘giraffe’on a correct occasion. In other words, the childmust have been exposed previously to the osten-sive pairing of the word with a correct event,e.g., with the presence of a giraffe. Such an os-tensive experience is necessary for transforminga probability that is practically zero into one thatis sufficiently high for enabling the beginning ofthe reinforcement process. And this suggests thatbehavior analysts who ignore the role of osten-sive experiences will not be able to give a scien-tifically correct account of the acquisition of ver-bal behavior.

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GeneralizationsPerceptual (Physical) Similarity. There are three

aspects of these ostensive processes that shouldbe considered. The first is the similarity generali-zation that is part of the process. The object towhich the child will afterwards point when beinginstructed ‘Show me a giraffe’ does not have tobe strictly identical to the original giraffe; it merelyhas to be “similar” in order to evoke the point-ing behavior. But which is the similarity that con-trols this generalization? This is not an easy ques-tion as can be shown by the difficulty of com-pleting the definitional sentence ‘x is similar to yif and only if … .’ But I will not engage here inthis problem, since I have dealt with it on severaloccasions (see, e.g., Stemmer, 1973a, pp. 50-56,1981, 1992; see also Quine, 1974, pp. 16-20).Roughly speaking, we can say that in the presentcase the similarity is a physical similarity. The childwill generalize from the original giraffe to physi-cally similar objects. Following Quine (1974), Iwill call the similarity that governs such elemen-tary generalizations perceptual similarity. (Experi-ments on stimulus generalization allow us to de-termine the range of the corresponding generali-zation classes, the classes that are determined byperceptual similarity, see, e.g., Schwartz, 1989;Walker 1987.)

Intraspecies Uniformity. The experiments onstimulus generalization point to a feature of ourgeneralization dispositions that plays a central rolein ensuring the high degree of success of verbalcommunication. This feature is the strong intraspe-cies uniformity of the dispositions. Most of theobjects that, for Mary, are perceptually similar toa giraffe are also for other people perceptuallysimilar to a giraffe; their generalization classesfrom a giraffe will be highly uniform. And sincemost native speakers of English have learned theword ‘giraffe’ by seeing a giraffe, this uniformityusually ensures a high degree of uniformity ofthe ranges of application of the word ‘giraffe’ forthese speakers. The classes of objects to whichthe speakers apply the word – i.e., the classes thatcontain the objects that, for example, evoke thepointing response to ‘Show me a giraffe’ or thatevoke the speaker response ‘giraffe’ to the ques-tion ‘What is this?’ – are highly uniform. This in-traspecies uniformity of our generalization dis-

positions is therefore one of main factors thatstand behind the high degree of success of ver-bal communication. (For more details on the cru-cial role of the intraspecies uniformity of ourgeneralization dispositions in ensuring a high de-gree of communicative success, see, e.g., Quine,1969; Stemmer, 1983, pp. 30-33.)

Functional Similarities. But physical (i.e., percep-tual) similarity is insufficient for accounting forthe generalizations that are involved in the learn-ing of words such as ‘toy’ or ‘tool.’ There is nophysical similarity between a doll and a toy-train.These generalizations are based on what I havecalled functional (or acquired) similarity. But for thissimilarity to be effective, the child must first un-dergo specific experiences. Thus in order to learnto apply the word ‘toy’ to different types ofobjects, the child must first have observed thatthese objects share a particular property: they havethe “toy-function.” However, a detailed analysisof these processes would lead us too far awayfrom our central topic. (The processes are dis-cussed in more detail in, e.g., Quine, 1974, pp.20-21; Stemmer, 1973a, pp. 50-56, 1980, 1983,pp. 80-84.)

Functional similarity plays a further and cru-cial role in verbal behavior. As has been shown inStemmer (e.g., 1973a, pp. 69-73, 1987a, 1990), itstands behind the child’s capacity to classify ver-bal expressions in syntactic categories. This ca-pacity then enables the child to acquire behaviorthat is controlled by so-called syntactic rules. Thisconclusion therefore contradicts Chomsky’s claimthat syntactic competence is not “obtainable from[examples] by any sort of ‘generalization’ knownto psychology and philosophy” (1965, p. 58, seealso Chomsky, 1957, 1959). Admittedly, whenChomsky made his claim, psychologists and phi-losophers had not yet discussed the empiricalevidence that shows the behavioral effects offunctional similarity. But they did so in later stud-ies. (For one of the first empirically-based appli-cations of functional similarity to verbal behav-ior, see Quine, 1974, p. 20-21; Stemmer, 1971.)

Long Term Effects and Physiological TracesThe second aspect that characterizes osten-

sive learning is the long-term effect of the learn-ing experiences. Mary will usually “remember”

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the correct use of the word ‘giraffe’ a long timeafter undergoing the ostensive experience in thezoo. Now, the unbiased, and scientifically inspired,explanation of this long-term effect attributes itto physiological factors (see, e.g., Quine, 1960,1974, 1975). The ostensive event had physiologi-cal, mainly neural effects, and as long as theseeffects persist, Mary will be able to perform thecorrect behavior with respect to the word ‘gi-raffe.’ Quine speaks in this connection of thephysiological trace that is left by the ostensiveexperience and that is later activated by relevantstimuli (1974, pp. 24-27). I will adopt here thisterminology. According to this physiological ap-proach, we account for Mary’s pointing to a gi-raffe upon hearing the command ‘Show me agiraffe’ in the following way. The ostensive ex-perience in the zoo left a physiological trace inMary’s organism, and when Mary now hears theword ‘giraffe’ (which occurs in the command),this trace is activated. This activation, together withthe sight of a (similar) giraffe, then evokes thecorrect response.

The physiological effects of ostensive experi-ences – the traces — are normal physical events,and experiments such as those described in Byrne(1987) and Hawkins and Kandel (1984), as wellas the results of procedures such as MRI or PETscans, have revealed some of their physico-chemi-cal properties. To be sure, in many cases, we arenot yet able to describe the physiological tracesin precise physico-chemical terms. But this shouldnot prevent us from appealing to such traces inorder to account for empirical phenomena. AsQuine says: “Lack of a detailed physiologicalexplanation of the states [traces] is scarcely anobjection to acknowledging them as states ofhuman bodies” (1960, p. 264).

To give an example from a different field.We attribute the brittleness of glass to its mo-lecular structure, and we will therefore attributethe breaking of a particular vase V to its particu-lar molecular structure. But in many cases, we areunable to describe the molecular structure of aparticular vase in precise physico-chemical terms.Nevertheless, we are clearly in agreement withsound scientific practice when we appeal to suchstructures in order to explain the occurrence of

certain events – in the present case, the breakingof vase V.

Listener BehaviorThe third characteristic of ostensive learning

is that its primary effect is listener behavior. Thus,Mary’s pointing to a giraffe when hearing ‘Showme a giraffe’ is an instance of listener behavior asis the handing over of a Jones-plug in Skinner’sexample. Except in a few instances, all verbalbehavior, including the behavior I will discusslater, begins as listener behavior (see, e.g., Stemmer,1973a, 1973b, 1992; see also Palmer’s observa-tion that “children typically are effective listenersbefore they are skilled speakers”, 1998, p. 13).But the fact that the primary effect of ostensivelearning is listener behavior does not diminish theimportance of the learning process for verbalbehavior in general, because normal children usu-ally acquire very soon the skills that allow themto go from listener behavior to speaker behav-ior.

Children also learn other types of terms inostensive learning processes. For example, theymay learn in such processes the relational expres-sion ‘x is-bigger-than y’ by hearing ‘Bill is biggerthan Fido’ while observing an appropriate situa-tion. The process, however, is highly complex,since the learning involves not only a generaliza-tion from the original ‘is-bigger-than’ situationto “similar” situations, but also awareness of theorder of the variables. First comes the term that“refers” to the larger object, then the expression‘is-bigger-than,’ and finally the term that “refers”to the smaller object. (We notice that the childobserved this order in the ostensive experience,cf. Stemmer, 1973a, pp. 125-127, 1987a.) Similarprocesses account for the learning of relationalterms with more variables such as ‘x gives y to z.’They, too, can be learned ostensively, and theyalso require awareness of the order of the vari-ables.

The above analysis adds important details toTonneau’s preliminary study of the learning pro-cesses based on the exposure to Pavlovian cor-relations. These details may enable behavior ana-lysts to engage in a more advanced analysis ofthese learning processes.

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Contextual Learning ProcessesIn later stages, children, as well as adults, learn

new terms in so-called contextual learning pro-cesses. These are non-ostensive learning processes,and the nature of the traces that are left by theprocesses are mainly determined by the verbalcontext. For example, as Skinner points out, aperson may become a competent listener of theterm ‘amphora’ by hearing an utterance of ‘Anamphora is a Greek vase with two handles,’ wherethe terms that occur in the verbal context ‘a Greekvase with two handles’ are “old” terms. Thus,when later requested ‘Show me an amphora,’ theperson “may point appropriately” (Skinner, 1957,p. 360). Now, a cognitivist explanation of the lis-tener effects of this contextual learning processmight attribute them to the fact that, by hearing‘An amphora is a Greek vase with two handles,’the person has learned to associate with the newword ‘amphora’ a (mental) meaning M, and thenature of M is determined by the meanings ofthe old terms that occur in the verbal context ‘aGreek vase with two handles.’ Meaning M nowdetermines that the listener response to ‘Showme an amphora’ is the pointing to an amphora(rather than to something else).

But a scientifically more correct explanationwill attribute the listener behavior to physiologi-cal factors. Hearing the verbal context ‘a Greekvase with two handles’ activates the physiologicaltraces corresponding to these old context terms,and this activation then determines the nature ofthe physiological trace that is left by the contex-tual event — the new trace that now correspondsto ‘amphora.’ And the nature of this trace thendetermines that ‘Show me an amphora’ evokespointing to an amphora (rather than to some-thing else).

In most instances of contextual learning, how-ever, it is much more difficult to point to thefactors that determine the nature of the physi-ological trace that is left by the learning events,for example, when people learn words such as‘consciousness,’ ‘depression’ or ‘happiness.’ More-over, some of these terms may be learned inmixed events, where both the environment andthe verbal context contribute to forming the lis-tener behavior. But a discussion of these learningprocess falls outside the scope of this paper. (In

Stemmer, 1983, pp. 131-156, I have examined inmore detail various aspects of contextual learn-ing; see also there the references to Osgood, 1953,and Staats, 1968. Note also that terms such as‘consciousness,’ ‘depression’ or ‘happiness’ areoften treated as theoretical terms, and severalmethodologists have investigated the connectionbetween these terms and environmental factors,e.g., Carnap, 1956, 1966. But I will not enter hereinto this highly interesting topic.)

The Learning of Mental Terms

We will now see that a physiological approachallows us to deal with Harzem’s project, namely,to account for the learning and use of so-calledmental terms without appealing to mysteriousentities. Suppose that two-year-old Tom has neverheard the word ‘pain.’ He now suffers from ap-pendicitis, and his parents ask him questions suchas ‘Are you in pain?’ or ‘Where do you have pain?’These ostensive pairing experiences — hearingan utterance of [Are you in] ‘pain’ paired withthe stimulation by the inflamed appendix — havespecific physiological effects; they leave a physi-ological trace. As a consequence, when this traceis afterwards activated by stimuli that are per-ceptually similar to the stimulations of the in-flamed appendix, such as an infected tooth, thehitting of a stone, or a new attack of appendici-tis, Tom may utter the English word ‘pain,’ i.e.,the word he heard in the ostensive experiences.That is, via a series of physiological processes,the hitting by the stone or the infected tooth or anew attack of appendicitis may evoke this verbalresponse from Tom.

We notice that by adopting a physiologicalapproach, we don’t have to assume the interven-tion of mental factors to account for Tom’s ver-bal behavior. Nor do we have to appeal to co-vert-behavior entities whose status is, to say theleast, problematic. By acknowledging the fact thatostensive experiences have physiological effects— that is, they leave physiological traces that areafterwards activated by perceptually similar stimu-lations — we can give a plausible materialist ac-count of the learning and use of so-called men-tal terms. (For simplicity, in the example above Ihave assumed that the behavior that is evoked

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after the ostensive pairing event is speaker be-havior. But, of course, the ostensive event mayalso generate appropriate listener behavior.)

Other mental terms such as ‘consciousness,’‘depression,’ or ‘happiness’ are usually learned incontextual or mixed learning processes. But byacknowledging the role of the physiological tracesthat are activated when the person hears the con-text terms, and that determine (partially, in themixed processes) the traces corresponding to thenew terms, we can give a materialist account ofthe use of these terms as well. (See also abovethe brief discussion of treating these terms astheoretical terms.)

The present account, which treats the factorsthat stand behind the learning and use of mentalterms as physiological, agrees with the views ofHarzem and of many other scientists. To be sure,as in the case of the trace corresponding to ‘gi-raffe’ (and of the molecular structure of vase V),we are presently unable to specify these factorsin precise physico-chemical terms. But this is noreason for ignoring the factors when explainingthe occurrence of phenomena that are clearlyderived from these factors.

Treating the factors that stand behind the learn-ing and use of mental terms as covert-behaviorentities (see, e.g., Moore, 1980, 2001) does notadvance us very much, because we are not onlyunable to specify presently the physical dimen-sions of these entities but we have no prospectsof doing so in the future either since, by defini-tion, covert-behavior entities are not supposedto be accessible to third persons. For example,there is no evidence that can tell us whether thecovert-behavior entities that evoke Tom’s utter-ance of the word ‘pain’ include one, two, or moreinstances of the letter ‘n,’ even though we caneasily observe that the overt response containsone instance of this letter. On the other hand, werecall that experiments as those described in Byrne(1987) and Hawkins and Kandel (1984), and theresults of MRI or PET scans, are throwing lighton the physico-chemical properties of the physi-ological traces that are left by particular events.

Actually, there is only a minor difference be-tween this physiological account of the learningand use of mental terms and the account usuallygiven by behavior analysts because the latter also

admit that “neurophysiology participates in theprivate behavioral event” (Moore, 2001, p. 174).The difference is the issue of covert behavior.Behavior analysts attribute not only physiologicalbut also behavioral features to the inner events,whereas the present account makes a more mod-est claim. It only attributes physiological featuresto the events. The physiological account is there-fore more parsimonious than the one given bybehavior analysts. It accounts for the same evi-dence, including the same behavioral evidence,while attributing fewer features to the inner events.(For the role of parsimony in deciding scientificissues – in the present case, for deciding that in-ner events have physiological but no behavioralfeatures – see e.g., Smart. 1963, pp. 8-13;Stemmer, 2001, p. 199.)

Our conclusions thus enable us to give a ma-terialist account of the use of mental terms. Thisaccount appeals neither to mysterious mental fac-tors nor to covert-behavior entities. But the ap-peal to physiological rather than to covert-be-havior factors has a further advantage. The no-tion of covert behavior is extremely alien to nor-mal thinking, even to people who are notcognitivists. But physiological factors are differ-ent, because most psychologists do acknowledgethe causal role of these factors. Therefore, thephysiological approach may facilitate a fruitfuldialogue with other psychologists. To be sure,cognitivists would like to add mental entities tothe physiological ones. But this is a more com-plex issue, and I cannot enter into this here. (Onhow to counter mentalist claims, see, e.g., Quine,1960, pp. 264-266, 1975; Stemmer, 1987b, 2001).

There is a further difference between thepresent treatment of the learning of mental termsand the one usually given by behavior analysts.The latter generally attribute the process to thedifferential reinforcement received for emittingthe word in the presence of the correct stimuli.For example, Moore’s (1980) account of thelearning of the word ‘pain,’ which is based onSkinner’s conclusions, assumes that the learningprocess takes place in a context of the three-termcontingency, which is “the fundamental unit ofanalysis for radical behaviorism” (1980, p. 461).In this learning process, a person is supposed toreinforce a child’s utterance of ‘pain’ on correct

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occasions. Moore points out the problems withthis process since the reinforcing person does nothave direct access to the correct occasion: theprivate painful stimulation. He suggests that theperson will base the reinforcement on public fea-tures that are associated in a reasonable regularway with painful stimulations. This conclusion isindeed plausible. There is, however, a further el-ement that is ignored by Moore, for the personcan start reinforcing the response ‘pain’ on cor-rect occasions only if the child emits the wordon such an occasion. But the probability that achild, who has never heard the word ‘pain,’ willemit this English word on a correct occasion ispractically zero. And even if the child has alreadyheard this word, e.g., when she heard hercaregiver saying ‘I have a pain in my neck,’ theprobability that she will emit the word when sheherself is painfully stimulated is still practicallyzero.

So what is missing here? As I pointed outwhen discussing the behavior-analytic account ofthe learning of ‘giraffe,’ what is missing is thatbefore the reinforcement can start, the child musthave heard at least once an utterance of the wordwhile she was in pain; that is, she must have beenexposed at least once to the pairing of the word‘pain’ with a painful stimulation. Such an expo-sure, or a couple of such exposures, transformsa probability that is practically zero into one thatis sufficiently high for the reinforcement to start(see also Stemmer, 2001, pp. 190-192). At thesame time, these events establish correct listenerresponses to the word.

The present analysis shows again that many,perhaps even most behavior-analytic accounts ofthe learning of verbal expressions are incomplete.They ignore the crucial role of the pairing eventsthat must precede the processes in which theemission of the verbal elements is differentiallyreinforced.

Action Names, Action Frames, andModifiers

Action NamesAs mentioned above, Tonneau has stressed

the role of ostensive learning — the processes hecalls Pavlovian correlations — in the acquisition

of a child’s verbal behavior. But as I have arguedin Stemmer (1996), these learning processes areusually preceded by still earlier learning processes.In these initial processes, children learn listenerresponses to action names such as to ‘bye-bye,’‘come here,’ ‘drink,’ ‘more,’ ‘don’t,’ ‘give me shoe,’or ‘drop sock’ (e.g., Benedict, 1979; Dromi, 1987;Smith & Sachs, 1990). These early learning pro-cesses are operant processes, since the responsesto the action names are established by a processof differential reinforcement.

Some of the action names that children learnin these events may be considered by adults asconsisting of two (or more) elements such as ‘goto sleep,’ ‘go to the corner,’ ‘drink the milk,’ ‘walkslowly,’ ‘give shoe,’ or ‘drop sock.’ It is unlikelyhowever that, in the very first stages, the responsesof naive children to the expressions are responsesto two separate elements: one that specifies theaction and one that specifies a property of theaction or an object with which the action is con-cerned. It is more plausible that the responses,e.g., going-to-a-corner, walking-slowly, giving-a-shoe, dropping-a-sock, are responses to undi-vided action names.

Action Frames and ModifiersBut in a second stage, and out of the previ-

ous instances, emergent listener behavior usuallydevelops, when children start to respond to novelcombinations of elements of the previouslylearned action names, as to ‘drink slowly,’ ‘walkto corner,’ or ‘drop shoe’ (e.g., Goldstein, 1983;Striefel, Wetherby, & Karlan, 1976; for similarresults in nonhumans, see, e.g., Herman, Richards,& Wolz, 1984; Savage-Rumbaugh, 1986). Thisemergent behavior suggests that some of the el-ements of the previously undivided action nameshave now acquired an independent status. Forexample, the elements ‘drink x,’ ‘walk x,’ and‘drop x’ now combine with the elements ‘slowly,’‘to-corner,’ and ‘shoe’ to evoke appropriate lis-tener responses. The former elements I call actionframes since they are expressed with the help ofvariables (see also Palmer, 1998; Stemmer, 1996;in logical discourse they are often called predi-cates with one or more arguments.). The latterelements I call modifiers (of action frames).

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We can now describe the emergent behaviorthat occurs in the second stage in the followingterms:

(1). In the second stage, the modifiers controlcertain properties of the responses that are con-trolled by the action frames.

(2). The properties that are controlled by themodifiers are the properties of the actions thatwere reinforced in the first stage.

Suppose, for example, that in a first stage, achild has learned to respond with the undividedaction of giving-a-shoe to the verbal command‘give shoe.’ This reinforced response had theproperty of being the giving of a shoe (rather thanof something else). Suppose further that, in asimilar manner, the child has also learned to re-spond to ‘drop sock.’ Finally, we assume that, sofar, the child has not yet heard the combination‘drop shoe.’ Then, in the second stage, the newcombination ‘drop shoe,’ which consists of theaction frame ‘drop x’ and the modifier ‘shoe,’may evoke the action that in the first stage wasreinforced in the presence of the verbal stimulus‘drop x,’ i.e., the dropping of something, andthis action will have a particular property P, namely,the property of the action that in the first stagewas reinforced in the presence of the verbalstimulus ‘shoe,’ i.e., the property of giving a shoe.That is, the action frame ‘drop x’ which occursin the command ‘drop x + shoe’ determines thenature of the action, and the modifier ‘shoe’ whichoccurs in the command determines that the re-sponse to this command has the property ofbeing the dropping of a shoe. (On verbal stimulicontrolling certain response properties, see alsoCerutti, 1989).

The above emergent behavior plays a crucialrole in the development of listener behavior (andtherefore indirectly in verbal behavior in general).It generates appropriate responses to “new” ver-bal stimuli: the new combinations of verbal ele-ments. The person’s listener behavior has become“productive” (cf. Catania & Cerutti, 1986). It isimportant to realize, however, that each of theelements of the new combinations must haveoccurred in a previous learning event of the abovetype. That is, the element must have been part ofa verbal stimulus that occurred in a previous ac-tion-name learning event; it must be an “old” el-

ement. (There are certain exceptions, for example,the listener may have learned a semantically re-lated version of a lexical item. But this is not theplace to deal with such exceptions.)

Presently, it is difficult to decide whether theemergent behavior — that is, the behavior evokedby the new combinations — derives from a spe-cial learning mechanism, or whether it derivesfrom the previous learning of the undivided ac-tion names, from the differential reinforcementof the responses to these names. But for the pur-pose of this paper, this issue does not have to bedecided. What is important is that animals alsoengage in such behavior. Therefore, the emer-gent behavior does not support Chomsky’s claimthat language derives from a Language Acquisi-tion Device that is restricted to humans (see, e.g.,Chomsky, 1965.)

So far, I have discussed action frames thathave only one variable. But very soon, more com-plex action frames may be learned, e.g., the frame‘Give x to y’ which takes two variables. But I willnot deal separately with these learning processes.(See also above the brief discussion of the os-tensive learning of ‘x gives y to z’ which, in itsdescriptive form, takes three variables.)

The present account, even though it is stilldealing with the initial stages of language learn-ing, is getting increasingly more complex and alsomore tedious, and many readers have probablylost their patience. They do admit that complexapplications of learning mechanisms to complexexternal stimulations stand behind verbal behav-ior. However, the topic becomes too compli-cated for their interests. But unless behavior ana-lysts are willing to hand over the study of thisbehavior to cognitivists, they have no alternativebut to deal with these complexities. There is noshortcut.

Ostensive Expressions as ModifiersFinally, in a third stage, which is not strictly

separated from the previous stages, ostensivelearning makes its crucial contribution to verbalbehavior. It establishes the expression that islearned in an ostensive pairing event as a modi-fier of action frames, and the nature of the modi-fication is determined by the nature of the non-verbal stimulus of the ostensive pairing event.

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Thus, in our previous example, the exposure tothe pairing of the word ‘giraffe’ with a giraffeestablishes the word ‘giraffe’ as a modifier ofaction frames — for example, of ‘give me x’ or‘drop x.’ The term ‘giraffe’ now controls a par-ticular property P of the responses to the actionframes, and the nature of P is determined by thenature of the non-verbal stimulus of the pairingevent: the giraffe. Therefore, the response to ‘Giveme giraffe’ consists of the action of giving some-thing, and this action has the property P of giv-ing a giraffe. Or in Skinner’s example, the expo-sure to the ostensive pairing of the term ‘Jones-plug’ with a Jones-plug establishes ‘Jones-plug’as a modifier of appropriate action frames,among them of ‘Please hand me an x,’ and themodifying character of ‘Jones-plug’ is deter-mined by the non-verbal stimulus of the osten-sive pairing event: the Jones-plug. Therefore, theresponse to ‘Please hand me a Jones-plug’ hasthe property of being the handing over of a Jones-plug rather than of something else.

Ostensive learning is of crucial importance forverbal behavior because it is such an easy andalmost effortless way to increase a person’s “lexi-con.” It establishes the behavioral effects ofmodifiers by a process that does not require therepeated reinforcement of a specific response tothe non-verbal stimulus of the ostensive events,e.g., the giraffe. Frequently, even a single expo-sure to an ostensive pairing event is sufficient toestablish a word as a modifier of action frames(see, e.g., Nelson & Bonvillian, 1973). To be sure,whenever the child correctly responds to a com-bination of an action frame with a modifier, e.g.,to ‘Give giraffe,’ ‘Drop Jones-plug’ or ‘Point toshoe,’ we usually reinforce the correct response.But this reinforcement only reinforces the evok-ing function of the action frames, e.g., of ‘give x,’‘drop x’ or ‘point to x.’ As is shown by single-exposure learning, no reinforcement is neededfor establishing the modifying role of modifierssuch as of ‘giraffe,’ ‘Jones-plug’ or ‘shoe.’ This iseffected by the exposure to ostensive pairingevents. Notice that this conclusion is indirectlyconfirmed by Lowe and Horne when they state(in my terminology) that the modifying functionof modifiers is established “whenever new ob-

jects are named by caregivers even in the absenceof explicit reinforcement” (1996, p. 318).

The modifying functions of ostensive expres-sions have often a more complex and indirectcharacter. Suppose that so far Mary has neverheard the word ‘big.’ Then, by hearing, for ex-ample, ‘This is a big doll’ while observing a largedoll, Mary may ostensively learn ‘x big y.’ Andthis ostensive learning event may then establishthe expression ‘big’ as a modifier of, e.g., “Giveme the z x.’ As a consequence of this modifyingrole of ‘big,’ Mary’s response to ‘Give me thebig giraffe’ may now be different from her re-sponse to ‘Give me the giraffe’ or from her re-sponse to ‘Give me the small giraffe’ (after shehas also learned ‘x small y’). Here, the modifyingrole of ‘big’ does not directly operate on the ac-tion frame ‘give me x.’ Rather, it modifies themodifying function of the modifier ‘giraffe.’ Butalthough this is a fascinating subject, I will notenter into this here. (Several aspects of these com-plex features have been examined in Stemmer,1987a, 1990; see especially the analysis of theclause ‘x who y,’ as in ‘The man who holds thepainting holds the book.’)

The Verbal ExplosionHorne & Lowe (1996) call our attention to

the verbal explosion phenomenon — the “veryrapid acceleration in name acquisition that occursafter approximately the first 10 to 20 names havebeen learned, normally when children are around18 months old” (p. 202). Horne and Lowe at-tribute the explosion mainly to an increase inechoic capacities. But since the role of echoic ca-pacities is restricted to the development ofspeaker behavior, the increase in these capacitiescannot explain the explosion in listener behavior,which not only precedes the speaker explosionbut which also is a necessary condition for thisexplosion.

The present analysis suggests a completelydifferent explanation. It attributes the verbal ex-plosion to the listener effects of ostensive learn-ing processes. Since these processes do not re-quire the repeated reinforcement of specific re-sponses but only the exposure to the pairing oftwo stimuli, they rapidly establish ostensive ex-pressions as direct or indirect modifiers of ac-

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tion frames — they incorporate the expressionsin the child’s lexicon in a very short time. To besure, some further conditions must be satisfiedfor ostensive learning to be effective. In particu-lar, the stimuli that occur in the ostensive pairingevents must be significantly salient (see, e.g., Quine,1974, pp. 24-27, 43-44; Stemmer, 1983, pp. 33-34, 77-78). But what is important in the presentconnection is that since these conditions do notinclude the repeated reinforcement of a specificresponse to the ostensively learned term, they donot prevent the rapid increase in the size of thechild’s lexicon.

Early listener behavior is thus established bythe combination of two types of events. The firsttype consists of the events that in a first stageestablish listener responses to action names, andthat in a second stage then give origin to re-sponses to two separate kinds of verbal stimuli:action frames and modifiers. The second typeof events consists of Pavlovian correlations, i.e.,the ostensive events that establish additional ver-bal stimuli as direct or indirect modifiers of ac-tion frames. In the former events, the responsesare established by operant conditioning processes;in the latter events, the responses are establishedby a process that is related to Pavlovian condi-tioning. (It is likely that some of these events havemixed features. But this is not the place to dealwith them.)

My conclusions show the important role ofthe events that establish listener responses to ac-tion names, action frames, and modifiers:

(1). The events are responsible for some as-pects of the productive character of listener be-havior and, once the transfer of listener behaviorto speaker behavior is achieved, of verbal be-havior in general.

(2). Together with ostensive events, the eventsare responsible for most aspects, probably evenfor all aspects, of early listener behavior.

(3). Because ostensive learning does not re-quire the repeated reinforcement of specific re-sponses to verbal stimuli, ostensive events are themain cause of the explosion of early verbal be-havior.

Conclusions

Harzem and Tonneau have shown that somefundamental changes have to be introduced inbehavior analysis in order to give it a more scien-tific status. In this paper, I have studied a numberof basic behavioral issues while making use oftheir conclusions. Three main topics have beenexamined here. First, various critical features ofostensive learning have been studied including is-sues such as the generalizations that characterizethe behavior generated in ostensive processes, thelong term effect of the learning events, and thelistener behavior that is established in these events.Moreover, I have briefly examined the learningof terms that have several variables and I haveanalyzed some aspects of contextual learningprocesses. Second, by adopting Quine’s physi-ological approach, I have shown how to accountfor the learning and use of so-called mental termswithout assuming mental or covert-behavior fac-tors. Finally, I have examined the operant pro-cesses that establish the controlling power of ac-tion names, action frames, and modifiers, and Ihave then connected between these learning pro-cesses and the ostensive processes. The latter pro-cesses establish the ostensive terms as direct orindirect modifiers of action frames.

The conclusions of this paper provide be-havior analysts with the tools to give a scientifi-cally satisfactory account of several basic issuesof human behavior. In particular, they enable themto replace the equivalence-class research program,which presently dominates behavior-analytic re-search of verbal behavior, by a more adequateprogram, and they also make it possible to ac-count for the role of mental terms without ap-pealing to mental or covert-behavior entities. Inthis way, then, the present paper may help us toarrive at a positive and fruitful reorientation ofbehavior analysis.

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