Back to Psychophysiological Home Page Behavioral And Brain Sciences (1993), 16:2, pp.392-398 Malmo_Furedy93.doc Continuing Commentary Commentary on Jaylan Sheila Turkkan (1989) Classical conditioning: The new hegemony. BBS 12:121-179. Abstract of the original article: Converging data from different disciplines are showing the role of classical conditioning processes in the elaboration of human and animal behavior to be larger than previously supposed. Restricted views of classically conditioned responses as merely secretory, reflexive, or emotional are giving way to a broader conception that includes problem-solving and other rule-governed behavior thought to be the exclusive province of either operant conditioning or cognitive psychology. These new views have been accompanied by changes in the way conditioning is conducted and evaluated. Data from a number of seemingly unrelated phenomena such as relapse to drug abuse by post addicts, the placebo effect, and the immune response appear to involve classical conditioning processes. Classical conditioning, moreover, has been found to occur in simpler and simpler organisms and recently even demonstrated in brain slices and in utero. Several research areas that have used the classical conditioning process as an explanatory model are integrated; teleological interpretations of the classically conditioned CR are challenged and some basic principles for testing conditioning in diverse areas are offered. Settling the stimulus-substitution issue is a prerequisite for sound nonteleological neural analysis of heart-rate deceleration conditioning Robert B. Malmo a and John J. Furedy b "Neuropsychology Laboratory, Department of Psychiatry, McGill University, Montreal, Quebec, Canada H3A 1A1 and "Department of Psychology, University of Toronto, Toronto, Ontario, Canada M5S 1AL In discussing the place of Pavlovian conditioning in psychology, Rescorla (1988) called attention to the currently intense interest of neuroscientists in the neural basis of conditioning, whose analysis Rescorla believes should be guided by the kind of teleological assumptions that Furedy (1989) argued against in commenting on Turkkan’s (1989) target article. In particular, Rescorla characterized Pavlovian conditioning as "the learning of relations among events so as to allow the organism to represent its environment" (Rescorla 1988, p. 151, our emphasis). The chief purpose of our commentary is to call attention to neuropsychological conditioning experiments by Malmo in which the UR (centrally elicited heart-rate deceleration in rats) appears to fit into the classical nonteleological and noncognitive S-R model that Rescorla (1988) rejects. Malmo (1963; 1965) developed a rat preparation that appears optimal for classical conditioning of heart-rate (HR) deceleration. Malmo's method incorporated the following features: (1) His US (lateral septal stimulation) is favorable in a number of respects: (a) the elicited HR deceleration is large-magnitude and unidirectional, avoiding initial HR acceleration, which is encountered with stimulation of the medial septal nucleus (Malmo 1964; Ross & Malmo 1979); (b) with appropriate electrode placement in the lateral septal area the short-latency HR deceleration is elicited directly instead of being secondary to a change in mean arterial pressure (see Ross & Malmo 1979) (in this respect the rabbit appears to differ from the rat in not exhibiting this desirable feature; see Van Dercar et al. 1970); (c) the UR is nonhabituating (unlike shock and loud-noise USs); and (d) the cardiac deceleration is not secondary to a change in respiration. (2) The CS is an exteroceptive (4K Hz tone) stimulus; when presented alone it has no effect on HR. (3) The relatively short 2.5 sec CS-US interval stands in contrast to the 8-10 sec US intervals used in some more recent studies by cognitively oriented workers. However, the 2.5 sec CS-US interval permits the measurement of the (anticipatory) CR on all reinforced trials, thereby avoiding complete dependence on CS-alone test trials to assess conditioning (Malmo 1963, pp 28-29). (4) The results (Malmo 1963, Fig. 11; see also Malmo 1965) yield highly orderly acquisition and extinction functions. As in the human negative-tilt preparation, the CR and UR are in the same (decelerative) direction (Furedy et al. 1989). (5) Various observations rule out nonassociative factors such as 392 BEHAVIORAL AND BRAIN SCIENCES (1993) 16:2 sensitization or pseudoconditioning. For example, there is no HR response to tone even after at least six sessions of brain stimulation alone. The scant attention paid to these remarkable findings is probably accounted for by the cognitive shift that was gathering force at the time they were published. Six years later, however, Malmo's (1965) conditioning study was referred to as the foundation for HR decelerative conditioning experiments with rabbits in Schneiderman's laboratory (Sideroff et al. 1971). For these investigators (and for others later on) there appears to be a compulsion (perhaps encouraged by the operant reinforcement properties of some of the US brain areas used) to find some feature, other than mere UR elicitation, that is indispensable for conditioning. We, on the other hand, believe it possible that for conditioning the only essential feature of brain stimulation may be its elicitation of HR deceleration. To the best of our knowledge, this possibility has not been considered recently. Investigators of HR classical conditioning in animal neuropsychological preparations appear to assume that the US must be "motivationally potent.' Having refuted the conclusion of Sideroff et al. (1971) that the US must be aversive to be effective, Sideroff et al. (1972) still expressed the view "that a motivationally potent US is necessary for establishing HR conditioning." They gauged motivational potency of the US in terms of its efficacy as an operant rein-forcer; and they attributed the failure of Sideroff et al. (1971) to obtain conditioning using low-intensity septal USs (which were nonaversive) to the presumed lower efficacy of septal, compared with hypothalamic, stimulation for intracranial selfstimulation (ICSS). Sideroff et al. (1972) used hypothalamic stimulation. This interpretation appears unparsimonious; and worse still, as we shall argue, it ignores a central issue concerning classical conditioning. No convincing evidence was presented to indicate that the low-intensity septal USs were as effective in eliciting short-latency, nonhabituating, large-amplitude cardiac decelerations as the high-intensity ones. Malmo's (1965) findings, which were not referred to by Sideroff et al. (1972), strongly suggest that it is the efficacy of UR elicitation rather than some vague "motivational" factor that is the crucial variable. Malmo (1965) found that the correlation between mean magnitude CRs (HR decelerations) and mean number of bar presses in ICSS was only .03. Moreover, subjects 5 and 8, who from the midway point on to the end of acquisition clearly stood out (with two others) as showing the largest CRs, could not be trained to self-stimulate. They showed no aversive reactions to the septal stimulation, which seemed to be motivationally neutral. From the findings of Gardner and Malmo (1969, Figure 1, p. 67) it appears that Malmo's (1965) stimulation sites in the septal area were dorsal to aversive septal sites that, contrary to the supposition of Sideroff et al. (1971), do not require higher current for escape than the dorsal stimulation sites require for approach. In short, the USs for those two superb conditioners appeared to be devoid of any operant reinforcement properties. These important leads from Malmo's laboratory have not been followed up. Instead, in neuropsychological studies, there has been a shift away from brain-stimulation USs to cutaneous shock USs with aversive properties (Hitchcock et al. 1989; Kapp et al. 1979). Left unresolved is the crucial issue of stimulus substitution by contiguity (in the absence of other reinforcement properties). We believe that the resolution of this central issue is a prerequisite for understanding the neural mechanisms underlying classical conditioning of HR deceleration. Our view is therefore contrary to the currently popular ideological approach exemplified in Rescorla's (1988) paper, which suggests that the nonteological, stimulus-substitution, S-R approach to Pavlovian conditioning is outmoded on scientific, evidentiary grounds. The findings from Malmo's laboratory have admittedly not been widely cited in the more "modern" treatments of conditioning, but as has been shown above, they are logically relevant for problems in the conditioning of brain-stimulation-elicited HR deceleration in animal preparations. There is also a parallel with similar issues in human autonomic conditioning where we believe S-R factors should be carefully considered along with S-S factors in a dual-process approach (see Furedy & Riley 1987), in particular, where one aim is the applied one of inducing the learning of a potentially medically useful target CR such as HR deceleration: S-R, response-learning factors need to be "remembered" (Furedy 1979), a position that contrasts with focusing solely on conditioning as "the learning of relations among events" (Rescorla 1988, p. 151). Classical conditioning: The hegemony is not ubiquitous Harald Merckelbach and Marcel van den Hout Department of Mental Health Sciences, University of Umburg, 6200 MD Maastricht, The Netherlands Electronic mall: h.merckelbach@ggk.rulimburg.nl In the past years, classical conditioning has gotten bad press, as noted, for example, by Davey (1987). Turkkan's (1989) excellent review does much to correct this bad reputation. It shows that the Pavlovian tradition provides fruitful procedures for studying such (seemingly) unrelated phenomena as taste aversion, immunosuppression, and drug dependency. One can use, as Turkkan chooses to do, a quasipolitical term, in casu "hegemony," to describe this happy state of affairs. Not all areas of interest to behavioral researchers are characterized by a hegemony of classical conditioning, however. For example, in the field of anxiety disorders, "traditional" classical conditioning accounts are on their way out (e.g., Marks 1977; Rachman 1977). This is all the more remarkable when one realizes that the first generation of behavior therapists were (and still are; Wolpe 1989) convinced that most clinical phobias and panic disorders are conditioned fear responses from confronting an unconditioned, painful event (e.g., Wolpe & Rachman 1960). Yet subsequent research has failed to find clear CS-UCS occurrences in the learning history of most anxiety disorder patients (e.g., McNally & Steketee 1985; Merckelbach et al. 1989a). In an attempt to overcome this and other problems, (e.g., the selectivity of fears; Costello 1982), a number of authors have tried to revise the Pavlovian theory of pathological fear. There is, for example, Seligman's preparedness hypothesis (1971), in which Pavlovian and Darwinian concepts were combined, and Eysenck's incubation theory [see Eysenck: "The Conditioning Model of Neurosis" BBS 2(1) 1979], in which the Napalkov effect (i.e., conditioned fear can act as a reinforcing event) is stressed. Reviews of the experimental (McNally 1987) and clinical (e.g., Merckelbach et al. 1989b) studies, however, have concluded that there is only meager support for an evolutionary preparedness factor operating in the etiology of human fears. Similarly, classical conditioning experiments that have sought to confirm the Napalkov phenomenon have yielded disappointing results (e.g., Nicholaichuk et al. 1982). It is no wonder, then, that researchers lose their faith in concepts such as preparedness and incubation, while cognitive theories (Eysenck 1988) are gaining influence. This is not to say that an empirically satisfying conditioning theory is impossible. One striking feature of preparedness as well as incubation theory is that neither made use of modern conditioning notions such as UCS inflation, latent inhibition, and blocking. It may well be that powerful theories emerge once these notions are incorporated in conditioning interpretations of anxiety (e.g., Davey 1989; Reiss 1980). These are future promises, however. For the moment, there is no such thing as a hegemony of classical conditioning in the field of anxiety disorders. Stimulus correlations in complex operant settings Francois Tonneau Department of Psychology, Temple University, Philadelphia, PA 19122 In her interesting target article, Turkkan (1989) effectively conveys the impression of a "classical conditioning hegemony" by taking up a datadriven approach and by reviewing a wide range of experimental results. The many advantages of such empirical approaches, however, should not make us forget the existence of various conceptual constraints on data selection and presentation. With regard to the target article, one's basic conception of behavioral explanation (e.g., Bolles 1984) necessarily influences the kind of "classical conditioning hegemony" to be proposed, the way in which the hegemony unifies experimental data, and the direction in which the hegemony could be further extended. Consider Turkkan's discussion of the relationships between classical conditioning (hereafter CC) and "memory," for example. Recall behavior is assimilated to the production of conditional responses (p. 133); it is then shown that recall can be related to temporal/ordering factors and variables such as intensity or contingency in ways that parallel CC phenomena. Does this exemplify some CC "determinants' of memory, as Turkkan puts it (p. 133)? Perhaps, but the data could just as well be taken to imply that memory processes determine CC. Indeed, in memory-based accounts of Pavlovian responding it is assumed that conditional responses result from the retrieval of an unconditional stimulus representation (Bolles 1985; Pearce & Hall 1980; Rescorla 1974; Wagner 1981). How the formal similarities reviewed by Turkkan (pp. 133-35) are to be interpreted thus clearly depends on one's underlying theoretical and conceptual choices: From a cognitive standpoint (e.g., Dickinson 1980), CC just represents a set of surface regularities and cannot serve as a basic behavioral explanation; CC is itself in need of explanation and assumes a derived status. Turkkan's reliance on CC as an explanatory tool is perhaps more readily understood in the context of a "functional analysis" (Wixted & McDowell 1989; see also Wixted 1989) that does not focus on mediating processes but aims at establishing wide-ranging relationships between independent and dependent variables. More generally, the target article (as well as the accompanying commentaries) can be examined in the light of Hineline's (1986; 1990) recent discussions of "organism-based" and "environment-based" modes of psychological theorizing. Especially relevant is Hineline's remark that the two explanatory modes entail different conceptions of psychological process: "For the organism-based position, process is what goes on inside the organism; process is said to mediate, or underlie behavior. From the behavior-analytic viewpoint, process is the very interplay between environment and behavior" (1986, p. 62). My BEHAVIORAL AND BRAIN SCIENCES (1993) 16:2 393 point is that both conceptions of psychological process can be found in Turkkan's paper, whereas many of the commentaries seem to have been written from an organism-based viewpoint. For example, an important theme of the target article appears to be the search for laws relating behavior to prior stimulus correlations (cf. the "litmus tests" 1-6, p. 123): This theme defines the possible field of a "CC hegemony" and accords well with environment-based psychological theory. On the other hand, CC results are attributed not to the stimulus correlations themselves (Skinner 1977) but to internal associative processes (pp. 134-35) - a cognitive explanation (see Schnaitter 1986, pp. 260-61) which could make sense only in the context of the "organism-based" theories (Dickinson 1980; Dickinson & Mackintosh 1978) that Turkkan criticizes for their heavy use of "hypothetical intervening variables" (p. 124). Thus it is not clear that Turkkan's simultaneous use of different explanatory modes leads to a consistent cognitive/behavioral integration, the feasibility of which remains debated (see Catania 1984; Hineline 1984; Lee 1990; Shimp 1989; Williams 1984). On the contrary, Turkkan's strategy has surely resulted in some confusions concerning the target article and may even explain the criticisms evident in some of the subsequent commentaries (e.g., C. Fields 1989; Jacobs 1989; on this point see Hayes et al. 1988, p. 106-7). Having detailed what is in my view the main conceptual problem with Turkkan's work, I can now take up the environment-based standpoint and try to extend one of the many interesting aspects of the target article - the analysis of CC processes as they relate to complex operant behavior (pp. 133-35). The remainder of my commentary is specifically devoted to this topic. As noted by Turkkan, in CC the operation that "strengthens" conditional responses is a contingent relationship, or correlation, between stimuli.l Now, whereas the traditional view of CC (e.g., Keller & Schoenfeld 1950, pp. 15-35) emphasizes the effects of stimulus correlations on respondent behavior exclusively, Turkkan (p. 123) leaves open the possibility that CC effects are much more pervasive: Environmental correlation may modify various behavioral functions of stimuli (cf. Staats 1968) and thus affect operant as well as respondent behavior. In support of this thesis, Table 1 presents stimulus functions in a more or less conventional way, from "elicitation" to various forms of contextual control, along with possible evidence of "strengthening" by CC relationships. It is clear that stimulus correlations can promote the emergence (or "transfer") of elicitation, Pavlovian occasion-setting, Pavlovian reinforcement, and operant reinforcement (see also Brown 1985; Dinsmoor 1985; Nevin 1983). Furthermore, to the extent that CC correlations "transfer" a whole range of behavioral functions from one stimulus to another, they constitute an important source of functional equivalence (cf. Goldiamond 1966; see Rachlin et al. 1986, p. 38, for a stimulating application of CC-based functional equivalence to the theory of choice behavior). 2 In this respect, it should be noted that most of the recent studies of functional equivalence in humans (e.g., Lazar 1977; Lazar & Kotlarchyk 1986) use a matching-to-sample methodology that involves various stimulus Table 1 (Tonneau). Classical conditioning-related emergence of stimulus functions Stimulus function Representative study elicitation Pavlovian reinforcement operant reinforcement occasion-setting discriminative control contextual control Jenkins & Moore (1973) Rashotte (1981) Fantino (1977) Holland & Forbes (1982) Boelens & Smeets (1990) ? Gatch & Osborne (1989) ? 394 BEHAVIORAL AND BRAIN SCIENCES (1993) 16:2 pairings (cf. Hayes et al. 1987, p. 364). Once the subjects have been taught to match stimuli in a consistent way, the pairings between samples and comparisons may produce a CC-based transfer of stimulus functions: Indeed, it has been observed that matching-to-sample promotes the transfer of discriminative and contextual control (Table 1; see also Catania et al. 1988; de Rose et al. 1988). Thus, the transfer of these functions in matching-to-sample studies may parallel the transfer of stimulus functions like occasion-setting in "pure" CC experiments (Table 1). The experimental analysis of such questions has just begun, however, and despite promising results (Boelens & Smeets 1990), the exact role of CC in the emergence of matching-to-sample functional equivalence effects is not yet known (see Hall 1988) 3 -hence my question marks following some studies in Table 1. On the whole, the results suggest a widespread influence of CC on the transfer/strengthening of stimulus functions (Table 1), but more experimentation along the lines of Boelens and Smeets's (1900) study is needed to confirm this "hegemony" of environmental correlations. To sum up: However CC itself is conceived (Tonneau 1990), the hypothesis that stimulus correlations underlie a wide range of functional equivalence effects deserves careful scrutiny (cf. Boelens & Smeets 1990). These correlations may work in concert with other behavioral processes to produce the observed transfer of function. In any case, Turkkan's target article is an excellent occasion for intensifying CCrelated research in complex operant settings; given the recent development of behavior-analytic alternatives to psychological associationism (L. Fields et al. 1984; 1990), the ensuing benefits could be numerous. NOTES 1. Although the precise meaning of "correlation" remains to be worked out (Williams 1983), effective CC relationships clearly include much more than simple contiguity (cf., for example, the relative waiting time hypothesis of Jenkins et al. 1981). The concept of correlation is accordingly used in this commentary to emphasize the whole temporal range of stimulus relationships that affect behavior. Note that contiguity can always be saved by appealing to "representations" (e.g., Holland 1981; Kehoe et al. 1987; see Branch 1977; Marr 1983; Tonneau 1990). 2. Functional equivalence (the idea that two stimuli are functionally equivalent to the extent that they control similar responses) is not to be confused with Sidman and Tailby’s (1982) notion of stimulus equivalence (see Hayes 1989). The present commentary addresses only functional equivalence. 3. Also see Dube et al. (1987) for a discussion of the possible relationships between CC and the reinforcer-specific effects observed in matching-to-sample studies. Author's Response Functions and effects of Pavlovian stimuli Jaylan Sheila Turkkan Division of Behavioral Biology, Department of Psychiatry and Behavioral Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD 21224 Electronic mail: med-bjst@jhuvms.bitnet The original target article (Turkkan 1989) questioned the widely held view that the classically conditioned response must provide a physiological or behavioral service to the organism for successful conditioning to occur. Malmo & Furedy dig a bit deeper and wider than this general nonteleological stance by further suggesting that the unconditional stimulus (US) need not function as a pun- isher or a reinforcer in other contexts for it to be effective in classical conditioning. That is, the US can be "motivationless," 1 a notion that was explored in some early review articles (e.g., Terrace 1973), but that has rarely been put to scientific test because of the difficulty in identifying strong stimuli that are ineffective in operant paradigms. From a historical perspective, identical electric shock intensities and food deprivation/magnitude levels have been effectively used across both operant and classical conditioning paradigms (see the many studies described in Hull [1943] without regard to Skinnerian or Pavlovian orientation). It makes intuitive sense to use a stimulus that has some strength for a strengthening operation, and it is known that intense stimuli often produce approach, escape/avoidance behavior, and physiological changes. In truth, one can question whether any suprathreshold stimulus can be considered truly neutral. Malmo & Furedy state that interoceptive lateral septal stimulation is neutral and ineffective for maintaining operant selfstimulation but that it is' effective as a US for bradycardic classical conditioning (Malmo 1965). They suggest further that this model was not pursued because of cognitive biases against stimulus-response (S-R) learning in favor of stimulus-stimulus (S-S) learning. But the cognitive Zeitgeist may have no bearing on why Malmo's heart-rate deceleration preparation was not pursued. Consider first the issue of practicality - the technology of administering exteroceptive shock, airpuffs to the eye, or administering food is simply less complex and less prone to error than stimulating the brain, which requires electrode locations and stimulation intensities to fall within narrow and critical limits (cf. Malmo 1964). There is also face validity in the use of the more standard USs as reflective of the realities of appetite and pain. But most important, Malmo's (1965) study - in part a test of whether the septal area that he was stimulating was operantly effective - was not conclusive because of the procedures that were used. Rats were initially trained with a classical conditioning procedure in which a tone was followed by septal stimulation as a US. Note, however, that the same rats were subsequently tested in an operant paradigm in which the septal stimulation was administered contingent on level-presses. Astute readers will immediately note that this is the very procedure that has been shown to produce "learned helplessness" (e.g., Seligman & Maier 1967) in a variety of species including rats. That is, initial experience with a US during classical conditioning retards later operant learning with use of the same stimulus. It is therefore not surprising that the two rats that showed the largest CRs during classical conditioning were the very rats who later failed to self-stimulate operantly! They had learned only too well, it seems, that their behavior bears no relation to the probability of occurrence of impending events, whether positive or aversive. Other rats in the same study did learn to self-stimulate, however, perhaps because their stimulation intensities were in some cases varied between the classical conditioning and the later operant self-stimulation phase of the study. Oddly, Malmo & Furedy’s current commentary directly contradicts the conclusions Malmo reached in the 1965 paper wherein he stated: "The evidence clearly indicates that the same stimulating voltage can serve as an effective US in classical HR conditioning and also [emphasis added] as an effective reinforcer for intracranial self-stimulation" (p. 5). Here he states that septal stimulation did not work as a reinforcer for intracranial selfstimulation in those studies. For some animals it did, and for some animals it did not. Studies of this nature are best done with separate groups of animals who experience either classical or operant paradigms so that potential crossover effects such as learned helplessness are avoided. Stimulating the lateral septal area may indeed be an intriguing "motivationless" US, but the experiments that Malmo & Furedy bring forward do not support their claim. Finally, the medical usefulness that Malmo & Furedy ascribe to transient bradycardic heart-rate reactivity is not supported by clinical practice, which is exclusively directed toward reduction of blood pressure for cardiovascular health. I can only second Malmo & Furedy's sentiment that the cognitive view appears to have led to a disappearance of the response (cf. also Gormezano et al. 1983). As a result, psychology has diverged from the only dependent measure that can be directly measured - the overt behavior of the organism. We now read about organisms down to the level of invertebrates representing, processing, planning, imagining, evaluating, remembering, correlating, and, yes, associating, rather than behaving. What the organism does after all these ruminations has been left out of the account. This is not a resurgence of dualism, as has been claimed (e.g., Denny 1986), but an unequivocal monism of the mind. Merckelbach & van den Hout's commentary regarding the etiology of phobias is puzzling because they also appear to contradict their own conclusions from an earlier study (Merckelbach et al. 1989a). Ninety-one phobic outpatients were administered a questionnaire that classified their phobia as having resulted either from a conditioning experience, vicarious learning, informational learning, or a mixture of these "pathways." Their results showed that conditioning experiences are common among phobic patients, with the overall frequency of conditioning experiences at 78%. Accordingly, in that discussion Merckelbach et al. (1989a) state "the present findings . . . seem to cast doubt on the view that conditioning events play a negligible role [emphasis added] in the etiology of phobias" (p. 660). Merckelbach & van den Hout's current contradictory assertion that conditioning plays a minor role in the etiology of phobia may be explained, however, by their definition of a "conditioning event" in that earlier paper. For those phobias categorized as "conditioned" they rarely found pure instances in which an explicit event (e.g., actual harm or pain) led to a phobia about stimuli or environments associated with that event. Instead, they found that patients reported experiencing a first panic attack consisting of frightening bodily sensations in a specific context and were subsequently phobic in that context. For a conditioning explanation to make any sense, a conditioning trial must have occurred. As they rightly ask in that study, "Why do first panics occur . . .?" (emphasis added). The last three decades have seen an explosion in the number of studies examining the relationship between adverse life experiences and the prevalence of disease, including psychiatric disorders (e.g., Dohrenwend et al. 1982). Life-event studies have almost invariably used retrospective designs in which patients' self-reported life experiences are correlated with the latency of onset, BEHAVIORAL AND BRAIN SCIENCES (1993) 16:2 395 severity, and prevalence of the disorder in question, as was done in Merckelbach et al. (1989a). Such study designs have inherent difficulties, however, that allow no easy conclusions about the relationship between reported adverse experiences and the development of phobia. For example, were the reported "first" panic attacks in fact the first, since panic experiences in childhood may either be forgotten or dismissed? Moreover, in Merckelbach et al. (1989a), patients may have been more likely to ascribe their seemingly irrational phobic behavior to an earlier "bad experience" (conditioning pathway) because it seemed less abnormal than to ascribe a phobia to "I saw something frightening on TV" (vicarious) or "I heard about it" (informational). Such "social desirability" factors that markedly bias questionnaire results have been well documented (Crowne & Marlowe 1964, pp. 3-10). Retrospective life-event studies in general have been widely criticized for a variety of potential experimental confounds (Kasl 1983), including subject selection (does the disease or disorder and/or the act of seeking help affect the recall and the reporting of life events?), control of events (the degree to which the adverse events are themselves brought about by the subject's disorder), timing of events (the onset date of the disorder in relation to the event), and the subjective, biased, and imprecise nature of subjects' reported events, particularly for those that are more distal in time. These and other confounds prompted some writers more than a decade ago to warn of extreme limitations on causal inferences in life event studies of mental disorders in particular (Dohrenwend et al. 1982). More prospective approaches to the study of adverse life events and their role in the development of psychiatric and physical disorders have been strongly urged (Kasl 1983). The etiology of phobia through classical conditioning mechanisms may be difficult to confirm in human studies, which are generally but not necessarily limited by a dependence on verbal report. Experimental analogues of panic, anxiety, and phobia have, however, been produced in the animal classical conditioning and operant laboratory for many decades (see a review in Lai & Emmett-Oglesby 1983; also Pavlov 1927/1960, pp. 290-91). Merckelbach & van den Hout note that some researchers are attempting to reconcile animal and human models of classically conditioned fear (e.g., Davey 1987). It may be as important at this stage of the research to develop clean methodologies that yield unambiguous findings as it is to engage in additional theory-building. Tonneau correctly points out the unintentional tug-of-war between "internal processes" and "functional relationships" as contradictory approaches to describing classical conditioning findings in the original target article (Turkkan 1989). The target article aimed for a functional analysis and attempted to derive general empirical laws from data resulting from such an approach (pp. 136-37). The term "associative processes" was used not so much in the sense of the internal "secrets behind the phenomena" (Malone 1981, p. 152) but more as an overarching term such as "learning"; that is, an abstract term nevertheless rooted in method, and, as Tonneau describes, in correlations between stimuli. Tonneau also explores transfer of stimulus function in classical conditioning as a parallel to functional equivalence effects in operant paradigms. "Transfer of stimulus function" as defined by Tonneau 396 BEHAVIORAL AND BRAIN SCIENCES (1993) 16:2 appears to be the same learning process conveyed by the earlier classical conditioning term "stimulus substitution." (I suggest that "substitution" is a better descriptor than "transfer," which might almost imply a yielding of control over behavior to another stimulus.) Some interesting studies using matching-to-sample designs have shown classical conditioning-like substitution of stimulus functions from first-order S+ stimuli that are directly paired with reinforcement to second-order stimuli that are correlated with the S+ stimuli (e.g., de Rose et al. 1988). Such studies point up once again the arbitrary assignment of stimulus properties as "eliciting" or "occasion setting" to classically conditioned versus operant learning. NOTE 1. Behavior analysts do not refer to motivational properties as residing within stimuli, but instead refer to external deprivation operations. References Boelens, H. & Smeets, P. (1990) An analysis of emergent simple discrimination in children. Quarterly Journal of Experimental Psychology 42B: 135-52. [FT] Bolles, R. C. (1984) On the status of causal modes. Behavioral and Brain Sciences 7:482-83. [FT] (1985) A cognitive, nonassociative view of inhibition. In: Information processing in animals: Conditioned inhibition, ed. 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