Unpredictable and Uncontrollable Events: A New Perspective ...

Journal of Abnormal Psychology1978, Vol. 87, No. 2, 256-271

Unpredictable and Uncontrollable Events: A New Perspectiveon Experimental Neurosis

Susan MinekaUniversity of Wisconsin

John F. KihlstromHarvard University

Recent work has shown that unpredictable and/or uncontrollable events canproduce a variety of cognitive, affective, and somatic disturbances to the orga-nism. These disturbances are compared to and found to be quite similar to thesymptoms of the classic cases of experimental neurosis described by Pavlov,Gantt, Liddell, Masserman, and Wolpe. The hypothesis is then developed thatthe common thread running through the entire experimental neurosis literatureis that in each case important life events become unpredictable or uncon-trollable, or both. This interpretation is contrasted with the earlier physiological,psychodynamic, and behavioral interpretations made by the investigators them-selves. The implications of this analysis of experimental neurosis for variousissues in the predictability-controllability literature are discussed—for example,the interaction between unpredictability and uncontrollability, the "threshold"for response to lack of predictability or controllability, and the lack versus theloss of predictability and controllability. Finally, the possible clinical relevanceof this new perspective on experimental neurosis is discussed.

In 1927 I. P. Pavlov reported an experi-ment by Shenger-Krestovnikova in which ahungry dog was placed in a harness for whatwas intended to be a straightforward salivaryconditioning experiment. When a circle waspresented, meat powder was forthcoming;

Editor's Note. This manuscript was receivedprior to publication of the special issue on learnedhelplessness (Vol. 87, No. 1). Therefore, the articlesin the special issue were not available as referencesto Mineka and Kihlstrom. Nevertheless, many ofthem are relevant to the issues discussed in thisarticle and should be consulted by the interestedreader.

This work was supported by grants to SusanMineka from the University of Wisconsin ResearchFoundation and Grants MH-271S6 and MH-2848Sfrom the National Instiute of Mental Health.

We thank L. Abramson, L. Benjamin, R. Render-sen, S. Rachman, D. Rush, M. E. P. Seligman, andS. Suomi for their many helpful and stimulatingcomments on earlier drafts of this article.

Requests for reprints should be sent to SusanMineka, Department of Psychology, University ofWisconsin, Madison, Wisconsin S3 706, or to JohnKihlstrom, Department of Psychology and SocialRelations, Harvard University, William James Hall,33 Kirkland Street, Cambridge, Massachusetts02138.

when an ellipse was shown, the food was with-held. Everything went as usual, and the dogacquired the discrimination rapidly. Then theanimal was required to make increasinglyfine discriminations, at which he succeededuntil the ratio of the semi-axes on the el-lipse reached 9:8. Pavlov (1927) describedwhat followed:

After three weeks of work on this differentiationnot only did the discrimination fail to improve, butit became considerably worse, and finally disap-peared altogether. At the same time the wholebehavior of the animal underwent an abrupt change.The hitherto quiet dog began to squeal in itsstand, kept wriggling about, tore off with its teeththe apparatus for mechanical stimulation of the skin,and bit through the tubes connecting the animal'sroom with the observer, a behavior which hadnever happened before. On being taken into theexperimental room the dog now barked violently,which was also contrary to its usual custom; inshort it presented all the symptoms of a conditionof acute neurosis. On testing the cruder differentia-tions they were also found to be destroyed. . . . Afresh development of the latter differentiation up toits previous exactness progressed twice as slowly asat first, but during the re-establishment of thiscrude differentiation the animal gradually becamequieter, returning finally to its normal state. . . .The 9:8 ellipse at its first application was corn-

Copyright 1978 by the American Psychological Association, Inc. 0021-843X/78/8702-0256$00.75

256

A NEW PERSPECTIVE ON EXPERIMENTAL NEUROSIS 257

pletely discriminated from the circle, but from thesecond application onwards no trace of a discrimi-nation was obtained, and the animal again entered astate of extreme general excitation with the sameresults as before, (p. 291)

Since Pavlov's classic report, many otherpsychologists have produced similar "neurosesof the experiment" by means of a variety ofprocedures. These have-included difficult dis-criminations, increasing delays before rein-forcement of a conditioned response, rapidalternation of excitatory and inhibitory con-ditioned stimuli, increasing numbers of aver-sive conditioning trials in a day, long periodsof restraint and monotony, punishment of anappetitive response, punishment of mistakeson insoluble problems, excessive numbers ofunpredictable shocks, excessive numbers ofuncontrollable shocks, to name a few. Thenumber of different procedures employed inthese studies has almost been matched bythe number of theories that have been elab-orated to explain the observed phenomena(e.g., Masserman, 1943; Pavlov, 1927;Wolpe, 19S8). In part, these interpretivedifferences may be a function of the sheervariety of procedures used to produce experi-mental neuroses. In addition, they mirror thehistorical conflicts between physiological,psychodynamic, and behavioral viewpoints inpsychology as a whole.

When one considers the range of pro-cedures that have been used to produce "ex-perimental neurosis," it is somewhat surpris-ing that they have all been classified underone common label. There is in fact no com-monly accepted empirical definition of experi-mental neurosis, and yet there do seem to beseveral general characteristics that all caseshave in common. First, some previouslylearned or adaptive behavior is no longerperformed in the test situation as a result ofsome procedural manipulation, intended ornot, made by the experimenter. Second, thebehavior that emerges in place of the pre-viously learned or adaptive behavior is gen-erally uncharacteristic of the animal's ordi-nary behavior and usually shows signs of ex-cessive autonomic arousal.

Despite the fact that these various pro-cedures all produce somewhat similar behav-ioral disturbances, it has proved extremely

difficult to abstract any single common de-nominator (or even a few) that could serveas a unifying explanatory principle. In oneprominent attempt to deal comprehensivelywith these phenomena, Broadhurst (1961)invoked the Yerkes-Dodson Law, assertingthat all the procedures increased motivationbeyond optimal drive level, with resultingpoor task performance and the release of fearresponses. However, in a later review, Broad-hurst (1973) retreated from this position andsuggested that "the search for the single so-lution [be] abandoned" (p. 745).

We, however, do not feel that such a searchis futile. On the contrary, we believe that acommon thread does run through all theseexperiments. In each case, environmentalevents of vital importance to the organismbecome unpredictable, uncontrollable, or both.In this article, we develop this point of viewand document it as well as is possible in anecessarily post hoc fashion, by reviewingthe classic studies of experimental neurosis.1

In doing so, we wish to emphasize that theimportance of understanding the experimentalneurosis literature does not necessarily stemfrom any very compelling phenotypic ortopographic similarities bewteen the disturb-ances observed by, say, Pavlov and thoseseen in the psychological clinic. Rather, therelevance of the experimental neurosis lit-erature today derives from the fact that theapparent sources or causes of experimentalneurosis seem highly similar or even identicalto certain factors that are also generally con-sidered to be important in human psychopa-thology.

Predictability and Controllability

Stimuli impinging on an organism may bestressful and produce debilitating emotional,somatic, or cognitive effects because they areintense, frequent, or of long duration or be-cause they produce conflict between approachand avoidance motives. However, even stim-uli that do not possess these properties canbe stressful or aversive if they are unpre-dictable or uncontrollable, or both. Over the

1 Others (e.g., Maier & Seligman, 1976; Seligman,197S) have made a similar argument, but theiraccounts are brief and highly selective.

258 SUSAN MINEKA AND JOHN F. KIHLSTROM

past 10 years, the elaboration of the conceptsof predictability and controllability has beena central topic in the psychology of learningand motivation, and this in turn has greatlyexpanded our understanding of fear, anxiety,stress, and depression (see particularly Selig-man, 1975; Seligman, Maier, & Solomon,1971).

Predictability

Consider two hungry rats bar pressing forfood in Skinner boxes who each receive threemoderately intense electric shocks over thecourse of their 2-hour bar-pressing session.One rat consistently receives a 1-minute lightpreceding each of his shocks. For the secondrat, the light is also presented but does notreliably predict the shock. During the firstfew days of this procedure, both rats show agreat deal of generalized suppression of barpressing. After several days, however, the firstrat manifests a typical conditioned emotionalresponse (CER) by suppressing bar pressingonly during the light. The second rat, bycontrast, continues to show a complete dis-ruption of bar pressing throughout the entire2-hour session. Apparently his CER is to theexperimental situation as a whole. Further-more, when the rats are sacrificed after 45days of such conditioning, the second ratshows extensive stomach ulceration but thefirst rat does not. These are the essentialresults of an experiment by Seligman (1968)that highlight the importance of the predicta-bility of aversive events.

In any conditioning experiment, twoparameters can be varied independently: both/>(UCS/CS) and #(TICS/OS) can vary from0 to 1, where p — probability, UCS = uncon-ditioned stimulus, CS = conditioned stimu-lus, and CS = the absence of CS. In a tradi-tional continuous reinforcement, classicalconditioning procedure, />(UCS/CS) = 1 and/KUCS/CS) = 0. In the past, learning theo-rists devoted some attention to the first ofthese two parameters in their studies of par-tial reinforcement in classical conditioning:They varied #(UCS/CS) but left />(UCS/CS) equal to 0. Only recently has much at-tention been devoted to the second parameter,

as when 0 < #(UCS/CS) < 1 (i.e., when theUCS is not reliably predicted). Because thevalue of these two parameters can be variedindependently from 0 to 1, as the values ofthe two probabilities approach each other, theenvironment becomes increasingly unpredict-able. Injthe limiting case, />(UCS/CS) = p(UCS/CS), and the CSs give the organism noinformation about the occurrence of the UCS.That is, the CSs and UCSs occur randomlywith respect to one another (Seligman et al.,1971).

A large body of literature now shows thatanimals and humans prefer predictable tounpredictable aversive events (Badia, Suter,& Lewis, 1967; Lockard, 1963, 1965; Pervin,1963) and that they may prefer signalled tounsignalled positive events as well (Cantor &LoLordo, 1970; Prokasy, 195,6). In a similarvein, animals and humans seem to prefer im-mediate over delayed shock (Badia et al.,1967; Knapp, Kause, & Perkins, 1959). Inaddition, unsignalled aversive events appearto be more stressful than signalled ones (e.g.,Badia & Culbertson, 1972). Seligman (1968)and Weiss (1970) both reported extensivestomach ulceration in rats exposed to unpre-dictable shocks; significantly less ulcerationwas observed in rats who received the sameamount and intensity of predictable shock.MacKintosh (1973) has further reported thatexperience with random presentations of CSsand UCSs retards the acquisition of a condi-tioned response (CR) at a later time, whenthese stimuli are paired. He called this"learned irrelevance." Thus, unpredictableevents have profound emotional, somatic, andcognitive effects on the organism.

Controllability

Now consider two dogs, each in a Pavlovianharness, with shock electrodes attached totheir feet and panels next to their heads.When the shock is turned on, one dog canterminate the shock by pressing the panelwith his head; for the second dog, panel pres-sing is ineffective in terminating the shock.The two dogs are yoked together so that bothreceive exactly the same amount of shock atthe same time; the only difference lies in the


controllability of the shock. The followingday each dog is placed in a shuttle box andgiven shock avoidance training. The first doglearns the avoidance response quickly. Thesecond dog, by contrast, does not learn theavoidance response and rarely even escapesthe shock. When the shock comes on, he liesdown on the grid and seems to accept theshock passively. On those occasions when hedoes make a response, he does not appear tomake the association between shuttling andthe termination of the shock because he con-tinues to accept the shock on future trials(Overmier & Seligman, 1967; Seligman &Maier, 1967).

As is the case with predictability in classi-cal conditioning, two parameters can be variedindependently in an instrumental conditioningsituation: ^(reinforcement/response) and p(reinforcement/response). Again these proba-bilities vary from 0 to 1. In a simple contin-uous reinforcement paradigm, ^(reinforce-ment/response) = 1 and p (reinforcement/response) = 0. Learning theorists have ex-tensively studied partial reinforcementschedules, in which the first parameter isvaried while the second is held constant atzero. Experiments such as those of Overmierand Seligman (1967) and Seligman and Maier(1967) first drew attention to the importanceof the second parameter. In particular, when/"(reinforcement/response) = ^(reinforce-ment/response), we can say that reinforce-ment is independent of responding, that is,the organism has no control over the rein-forcement (Seligman et al., 1971).

There is an extensive literature on the ef-fects of uncontrollable aversive and appetitiveevents in humans and animals. Subjectively,humans rate controllable noise as less aver-sive than uncontrollable noise of equal dura-tion and intensity. Controllable noise is alsoless disruptive to ongoing behavior (Glass &Singer, 1972). In terms of physiologicalstress effects, Weiss (1971) reported that ratswho received controllable shocks showed sub-stantially less stomach ulceration than theiryoked partners, who had received the sameamount of shock but had not had control overshock termination. In addition to direct stresseffects, the behavioral sequelae of exposure to

uncontrollable aversive events are numerousand wide ranging. In animals, new associa-tions between responses and reinforcements(same or different) are acquired slowly (e.g.,Goodkin, 1976; Maier & Seligman, 1976); inhumans, problem-solving tasks, such as ana-grams, are performed less efficiently (Hiroto& Seligman, 1975). In general, the subjects ofthese treatments become more passive. Forexample, animals have been shown to respondmore slowly, to display less shock-elicitedaggression, and to lose interest in sex andfood (the latter also resulting in weight lossand loss of position in the dominance hier-archy) (Maier, Anderson, & Lieberman,1972; Miller & Weiss, 1969; Seligman, 197S).Thus, exposure to uncontrollable aversiveevents can create a variety of profound af-fective, cognitive, and physiological disturb-ances for the organism.

Although the literature on the effects ofuncontrollable appetitive events is much lessextensive than that on aversive events, theredo appear to be parallel cognitive and moti-vational deficits produced by exposure tosuch events. Welker (1976) and Wheatley,Welker, and Miles (1977) have found thatpigeons and rats given exposure to response-independent food were later retarded at learn-ing to make a response to deliver the food tothemselves. Goodkin (1976) also found thatrats given pretreatment with inescapableshock or free food were later retarded atacquisition of a shuttle box escape response.And in humans, Kurlander, Miller, and Selig-man (cited in Seligman, 197S) found that ex-posure to insoluble discrimination problems(hence uncontrollable reward) resulted in areduced level of competitiveness when thesubjects were later required to play a Priso-ner's Dilemma Game.

Overlap Between Predictabilityand Controllability

It is, of course, logically impossible tomanipulate the factors of controllability andpredictability completely independently. Al-though predictable events are not necessarilycontrollable (as in a classical conditioningparadigm), controllable events necessarily in-volve a certain amount of predictability, at


least over stimulus offset. A number oftheorists (e.g., Averill, 1973) have assertedthat it is this element of predictability in-herent in controllability that is the criticalelement accounting for the importance of con-trol. Others (e.g., Seligman, 1975) have ar-gued that control is important for additionalreasons having to do with the sense of mas-tery or competence that it teaches the organ-ism. At present this issue remains unresolved(see Miller, in press, for the most recent re-view of this issue).

Despite the difficulty in making clear-cutinterpretations of what effects are due towhich factor, it is apparent from the preced-ing brief review that the unpredictabilityand/or uncontrollability of aversive eventscan have many deleterious consequences onaffect and cognition as evidenced by behav-ioral and somatic changes in the organism.Similar, although perhaps less pronounced,cognitive and motivational deficits also appearto follow experience with uncontrollable and/or unpredictable appetitive events, althoughthe relevant literature on this topic is sparse.In sum then, the lines of evidence just re-viewed converge on the proposition that it isimportant for the organism that certain events(e.g., acquisition of food, escape from pain)occur in a predictable and/or controllablemanner.

Symptoms of Experimental Neurosis

Thomas and Dewald (1977) recently com-pared the symptoms that follow exposure toan experimental neurosis paradigm with thosefollowing exposure to uncontrollable shock.Using a variant of the Shenger-Krestovni-kova procedure in cats, Thomas found thatas the discrimination became increasingly dif-ficult, his cats ceased to initiate their ownPavlovian conditioning trials. Furthermore,their behavior became highly agitated andincluded "sudden vigorous outbursts of escapeand aggressive behaviors." This agitated statewas followed several days later by a stage ofdepression and lethargy. Virtually identicalbehavioral disturbances resulted from ex-posure to uncontrollable electric shock. Dur-ing the first few inescapable shocks, the catsstruggled and were highly agitated. Soon,

however, the agitation disappeared and theanimals displayed virtually no reaction to theshock. This "striking lack of affect or overtsigns of fear" (p. 224) carried over into thetest session the next day. So "both syndromesappear to follow a similar course—a period ofintense agitation followed by a stage oflethargy and depression" (p. 225). Further-more, similar loci in the brain seem to beimplicated in the two syndromes, and reward-ing brain stimulation can be used to restorenormal behavior for both.

No other direct comparisons have beenmade between the symptoms of experimentalneurosis and those created in situations ofunpredictability or uncontrollability. Never-theless, the cognitive and motivational defi-cits and the affective and somatic disturbancesthat pervaded the predictability-controllabil-ity literature also stood out in our review ofthe experimental neurosis literature. First, wenoted the frequency with which the investi-gators of experimental neurosis stated thattheir animals seemed to have lost their abil-ity or motivation to perform even the simplestof learning tasks. Such cognitive and/or moti-vational deficits parallel those noted above inour discussion of predictability and controlla-bility. Second, we noted that experimentallyneurotic animals generally showed affectiveand somatic changes in one of two directions.Some became very agitated, with increasesin general activity level and signs of highautonomic arousal (increased breathing rate,piloerection, struggling, howling, etc.). Othersshowed decreased activity levels and gen-erally looked passive and withdrawn, some-times becoming socially isolated from theirconspecifics. Some animals passed throughboth of these stages at different times. Nearlyall animals showed feeding disturbances, atleast in the experimental situation. Thesestages appear to resemble, respectively, thestate of chronic fear or "anxiety" and thestate of passivity and "depression" describedabove as occurring in situations of unpredict-ability or uncontrollability (Seligman, 1975).

The experimental neurosis literature andthe predictability-controllability literatureprobably represent the two most salient ex-amples of gross behavioral and physiologicaldisturbance ever produced by purely behav-


ioral manipulations. Although direct com-parison of the kinds of disturbances createdis impossible to perform retrospectively,many compelling similarities do appear toexist (see especially Thomas & Dewald,1977). The natural question to follow thisobservation, then, is: Have similar factorscaused the similar disturbances described inthe experimental neurosis and the predict-ability-controllability literature? In the nextsection we explore this possibility by ana-lyzing the classic demonstrations of experi-mental neurosis. In each case we argue thatthe behavioral disruptions observed can betraced to the inability of the subject to pre-dict and/or control certain events of impor-tance to him.

Reanalysis of Classic Demonstrations ofExperimental Neurosis

We now turn to those studies of experi-mental neurosis that have gained specialprominence in the literature. We restrict ourattention to the studies of Pavlov, Lidell,Gantt, Masserman, and Wolpe because allother studies of experimental neurosis haveinvolved minor variations on their procedures.Within this domain, however, we aim to becomprehensive. We recognize that our analy-sis is post hoc because none of the experi-ments was designed with our hypothesis inmind. In fact, with the exception of Masser-man and Wolpe, most investigators werecontent merely to demonstrate the experi-mental neurosis phenomenon. By and largethey did not proceed with the next step, arigorous experimental analysis, and hence ourjob of interpretation is all the more difficult.We consider our account valid to the extentthat it can be compellingly applied to eachindividual study. At various points we offersuggestions about how a more rigorous ex-perimental test of our hypothesis might beconducted.

The Shenger-Krestovnikova Study

The importance of predictability is partic-ularly apparent in the study of Shenger-Krestovnikova described at the outset (citedin Pavlov, 1927, pp. 290-293). A hungry dog

receives food in the presence of one CS (cir-cle) and not in the presence of another CS(ellipse). The dog rapidly learns to predictwhen food will occur. As the ellipse becomesmore and more circular and the discrimina-tion increasingly difficult, there comes a pointwhen the dog can no longer reliably predictwhether a given CS will be followed by food.This state of unpredictability persisting over3 weeks must be very stressful for a hungrydog, and the resulting disturbance in his be-havior is not surprising. When the discrimina-tion is made easy again and predictabilityrestored, his behavioral disturbance disap-pears. That he initially has difficulty relearn-ing the easy discrimination is in line with theresults of MacKintosh's (1973) study onlearned irrelevance and Seligman's (1968)study of associative retardation. When thesemi-axes of the ellipse again occur in theratio of 9:8, the behavioral disturbance re-appears, reflecting the loss of predictabilitythat has occurred, now for the second time.

It may be argued that if the two CSs arefunctionally equivalent, then £(UCS/CS+)= .5 and />(TICS/OS) = 0, and the appear-ance of food is not really unpredictable in thestrict sense at all. According to this argu-ment, the Shenger-Krestovnikova experimentsimply involves partial reinforcement, and theeruption of experimental neurosis is truly sur-prising. However, this objection fails to recog-nize that for an animal who has been in adiscriminative conditioning situation for along time, the two most salient parametersare not #(UCS/CS+) and />(UCS/CS) butrather £(UCS/CS+) and #(UCS/CS-). Ina typical discriminative conditioning experi-ment, KUCS/CS+) = 1, #(UCS/CS-) =0, and £(UCS/CS) = 0. As long as these twomost salient parameters are unequal, onset ofthe UCS is at least somewhat predictable. Inthe Shenger-Krestovnikova study, however, atthe point where the circle and the ellipse canno longer be distinguished, p(UCS/CS+) =#(UCS/CS-) = .5. Thus, in terms of theparameters that are salient for the animal, thesituation is subjectively one of unpredictabil-ity rather than one of partial reinforcement.

We speculate that the important variableresulting in the behavioral disturbance is the


loss of predictability in an animal who oncepossessed it in the context of discriminativeconditioning. In principle, if a dog with noextensive previous history of discriminationlearning were simply presented with a circleand a 9:8 ellipse and only reinforced for thecircle, even over a period of many weeks,experimental neurosis would undoubtedly notemerge (see Kimmel, 1975, for a similar ar-gument). In view of the complete lack ofresearch on the loss of predictability, as op-posed to the simple lack of it, we feel thatthe Shenger-Krestovnikova study illuminatesan important topic for future study.

Other Studies jrom Pavlov's Laboratory

In a strict historical sense, priority in thediscovery of experimental neurosis goes toErofeeva in 1912 (cited in Pavlov, 1927,pp. 289-290). In her experiment, a dog wasinitially presented with a mild electric shockto the skin as a CS in a salivary conditioningexperiment. Gradually the intensity of the CSwas increased until it was "extremely power-ful" and a stable conditioned response wasmaintained over several months. An attemptwas then made to generalize the CR by ap-plying the CS (strong shock) to new placeson the skin. After the CR had been general-ized to a number of new places, suddenly a"violent defense reaction" occurred, and alltraces of the salivary CR, even to the originallocation and intensity of the CS, disappeared.(Two other dogs were run in similar pro-cedures, and both showed the same sort ofdisturbance.) Here the CS is a traumaticstimulus in its own right, and it seems likelythat it would be important for the animal tobe able to predict where on his body thatstimulus will be applied. In the absence ofthis kind of predictability, the animal cannotmake any kind of postural adjustment orpreparatory response to mitigate the effects ofthe shock. What appears to be critical, then,in producing this disturbance is that the ani-male loses his ability to predict the point onhis body where the traumatic stimulus will infact be applied. Note that our emphasis hereis on the importance of being able to predictwhere a traumatic stimulus will be applied.In the past the importance of this variable

has not been investigated because experi-menters have exclusively manipulated pre-dictability over when a traumatic stimuluswill be applied. The results of the Erofeevastudy suggest an important topic for futureresearch.

In 1913 Petrova (cited in Pavlov, 1927,pp. 293-294) conditioned a dog to makesalivary responses to each of six differentstimuli. Initially the interval between any ofthe CSs and the UCS was 5 sec; graduallythe intervals were increased by 5 sec per day.When the CS-UCS interval reached 120 sec,behavioral disturbances began to appear, andwhen the interval was further extended to180 sec, "the animal became quite crazy" (p.294). Here we are reminded of the studiescited earlier, which indicate that, at least foraversive events, subjects prefer short to longinterstimulus intervals (Badia et al., 1967;Knapp et al., 1959), presumably because theycan predict events more accurately over theshort run. If so, then increasing the CS-UCSdelay effectively decreases the animal's abil-ity to predict the occurrence of the UCS.Furthermore, if one considers that a long-delay CS has several components, some ofwhich are excitatory, some relatively neutral,and others inhibitory (Pavlov, 1927; Res-corla, 1967), then the predicament of thisanimal becomes more apparent. Each day,what was previously the excitatory part ofthe CS now must become inhibitory (i.e., thatpart of the CS which previously informed theanimal that food was about to appear now nolonger predicts food). Konorski (1967) hasdocumented that the transformation of CRsfrom excitatory to inhibitory, or vice versa, isalways a difficult process, and the results aregenerally unstable. He, in fact, has observedexperimental neurosis developing during thetransformation of an excitatory CR into aninhibitory one (1967, p. 333). In the Petrovaexperiment, this state of shifting predictionspersists day after day and is compounded bythe unreliability of the animal's internalclock, which presumably increases as thedelay increases. According to our theory,neurosis would not have resulted if long-delayCSs had been used from the start of condi-tioning. In this case there would have been no


shifting predictions from day to day and noloss of a capacity to predict the UCS. Infact, Pavlov sometimes used this procedureand did not report any instance of experi-mental neurosis developing.

A fourth demonstration of experimentalneurosis, noted only briefly by Pavlov (1927,pp. 301-302), occurred when a dog suddenlyreceived a previously established CS+ im-mediately following a CS— for a salivaryconditioned reflex. Although the details ofthis experiment are lacking, it seems likelyonce again that this was a situation in whichthe dog's capacity to predict what wouldhappen next was exceeded. Generally in adiscriminative conditioning experiment, p(UCS/CS+) = 1, />(UCS/CS-) = 0, and#(UCS/CS) = 0. Because CS- is normallyfollowed by an interval of CS that is also areliable predictor of UCS, the sudden appear-ance of CS+ immediately following CS—presents a contradiction similar to the onenoted earlier. A "stimulus" (interval follow-ing CS-) that once reliably predicted UCS,

-is now filled with CS+, a reliable predictorof UCS. The dog's capacity to predict whenfood will occur is strained or exceeded. Inanother account of this experiment, Pavlov(1961, p. 78) noted that when this procedurewas repeated many times, the intensityof the disturbance gradually decreased.Eventually this procedure no longer evokedany disturbance. By our analysis, this is notsurprising because the interval following theCS— by this point no longer predicts UCS.In fact, there is now a sequential compoundCS (CS- CS+) that reliably predicts UCS.Such a compound CS would probably func-tion like any long-delay CS, with the initialparts being inhibitory and the later partsexcitatory.

So although Pavlov attributed his dogs'agitated and disturbed behaviors in each ofthese situations to a "clash" between corticalexcitation and inhibition, we believe that theantecedent conditions can each be character-ized as having created a loss of predictability.Actually, from an operational and functionalstandpoint, the situations that create clashesof excitation and inhibition are generally

identical to those that create a loss of pre-dictability. The advantage that our theoryhas over Pavlov's is that it does not rest onoutmoded, quasi-neurophysiological concepts.

Gantt

W. Horsely Gantt, who spent some time inPavlov's laboratory, helped to introduce theconcept of experimental neurosis to this coun-try by virtue of his translation of Pavlov's(1928) lectures. His own experiments fol-lowed Shenger-Krestovnikova's procedure forinducing experimental neurosis, by employingdifficult discriminations in salivary condition-ing with dogs (Gantt, 1944). Following Pav-lovian theory, he has interpreted the behav-ioral disorders that he observed to be theresult of a clash of excitation and inhibition(Gantt, 1944, 1971). Following our earlieranalysis of Shenger-Krestovnikova's study,however, we believe that the experimentalneurosis is related to the loss of predictabil-ity that occurs when discriminations becomeextremely difficult or impossible.

Aside from replicating and extending Pav-lov's procedures, Gantt made several uniquecontributions to our knowledge of experi-mental neurosis, stemming from the manyyears of careful observations that were madein his laboratory. For example, the case his-tories of his dogs Peter, Fritz, and Nick(Gantt, 1944) underscore Pavlov's earlieremphasis on the contribution of individualdifferences in temperament to susceptibilityto experimental neurosis, to symptomaticmanifestations of breakdown, and to prog-nosis for recovery. Furthermore, his obser-vations of long-term symptomatic changesled him to originate the concepts of schizo-kinesis and autokinesis (Gantt, 1937, 1953).Autokinesis refers to the spontaneous devel-opment of new symptoms over time, evenafter the discontinuation of the experimentalprocedure. In sckizokinesis, separate com-ponents of a conditioned reflex develop at dif-ferent rates and persist for different periodsof time, resulting in a disharmony or cleavagein behavioral, emotional, and psychophysio-logical response systems, which is an impor-tant aspect of our current understanding offear (e.g., Lang, 1968). The importance of


these two concepts in interaction with pre-dictability and controllability has not yet beeninvestigated but would appear to be an im-portant topic for future research.

Liddell

Perhaps the most prolific investigators ofexperimental neurosis were Liddell and his co-workers at Cornell, who over many yearsstudied experimental neurosis in sheep, goats,and pigs, as well as in dogs (Anderson & Lid-dell, 1935; Anderson & Parmenter, 1941;Liddell, 1944). Their procedures were alsoPavlovian, although they generally employeda defensive leg-flexion CR, with shock as theUCS, rather than a salivary CR. This differ-ence is important because in defensive clas-sical conditioning, the subject is clearlyplaced in a situation in which he/she has nocontrol over the occurrence of aversive events.Moreover, it was often the case that the in-terval between the CS and the UCS wasvariable (e.g., Anderson & Liddell, 1935,Sheeps 2 and 3). Thus, the onset of shockwas often somewhat unpredictable, as well asuncontrollable. These threads of unpredicta-bility and uncontrollability run throughoutthe Cornell group's studies, and are furthercompounded by other aspects of the pro-cedures employed.

Five different procedures were found toproduce experimental neurosis (Anderson &Parmenter, 1941; Liddell, 1944). Often sev-eral of these were employed concurrently,making it difficult to assign definite responsi-bility in each particular case. Two of theseprocedures involved variants of the difficultdiscrimination and increasing delay of the CSparadigms studied in Pavlov's laboratory. Asdiscussed earlier, these are both situations inwhich the animal loses its ability to predictwhen the UCS will occur, with results thatare even less surprising in view of the factthat the UCS employed was shock rather thanfood. A third procedure, which was acciden-tally found to produce experimental neurosis,involved increasing substantially the numberof conditioning trials presented each day. Ifthe experimental situation was already one inwhich the controllability and sometimes thepredictability of aversive events were absent,

increasing the number of conditioning trialsand consequently the duration or density ofthe experimental session may conceivablyhave multiplied the stress experienced by theanimals.

The two remaining procedures involved,respectively, alternating the presentation ofCS+ and CS— for shock according to a rigidtime schedule and presenting a long series ofCSs— in order to establish a simple discrimi-nation (extinciton method). Frankly, fromthe point of view adopted in this article,these procedures alone should not have pro-duced behavioral disorders. In both cases, theoccurrence of environmental events seemsperfectly predictable. We suspect that theselast two procedures, neutral or only mod-erately aversive in and of themselves, werecompounded by other factors, both proceduraland constitutional, which were actually re-sponsible for the disturbed behavior. For ex-ample, Anderson and Parmenter's (1941)Sheep D showed signs of experimental neu-rosis following a long series of CS— trialspresented in an attempt to establish an easydiscrimination. The authors remarked, how-ever, that this sheep was extremely nervousand "skittish" even before he was introducedto the laboratory. Additionally, some sheep(e.g., Sheep 8) showed signs of experimentalneurosis when rhythmic alternation of CS+and CS— was introduced, but others (e.g.,Sheep 11) showed no signs of experimentalneurosis even over several years of similarexperience. In both instances, it seems thatconstitutional factors, rather than the experi-mental procedures themselves, may haveplayed a primary role in the breakdownobserved.

Initially LiddelFs group attributed experi-mental neurosis to a variety of neuroendo-crine changes (e.g., Anderson & Parmenter,1941). Later, however, Liddell (1944, p. 393)offered an interpretation very much in ac-cord with our own, noting that the domesti-cated animal already lives under conditions ofconsiderable restraint—a condition that isexacerbated by the exigencies of the labora-tory experiment. Restraint, or loss of control,in either situation alone may be disturbing tothe animal, and the two in conjunction arelikely to be even more stressful. Liddell often


emphasized that laboratory experimentswhich did not involve restraint of movement(as did the Pavlovian harness), such as in-soluble mazes, did not produce experimentalneurosis. Moreover, we noted that in the caseof Sheep 8 (Anderson & Parmenter, 1941),signs of experimental neurosis disappearedwhen the defensive conditioning was carriedout in a situation that permitted freedom ofmovement. Although Liddell's experimentswere not conducted with the operational con-cepts of controllability and predictability inmind, it is clear that he considered similarconcepts (especially control) to be critical.

Masserman

In procedural terms, the work of Masser-man contrasts sharply with that of Gantt andLiddell, which was conducted around thesame time. Whereas Gantt's and Liddell'smethods were closely tied to Pavlov's, Mas-serman used a punishment procedure to in-duce "motivational conflict" in his cats andmonkeys. In his early experiments, cats weretrained to associate a signal with the avail-ability of food. After the cats reliably openedthe lid of the food container upon presenta-tion of the signal, a variety of proceduralchanges were introduced. For example, somecats were prevented from reaching the foodbox, others were put on a partial reinforce-ment schedule, and still others were punishedwith an air blast or electric shock the momentthey opened the lid to feed. Only the punish-ment of feeding resulted in profound andpersistent behavioral changes. Complete ces-sation of feeding in the box generally ensuedrapidly in the punished animals. Moreover,the animals showed marked changes in ac-tivity levels, strong behavioral and psycho-physiological signs of fear of the signal,stereotyped defensive reactions, alterations inthe dominance hierarchy, and displacementactivity (Masserman, 1943, pp. 67-71).These behavioral changes persisted over manymonths, despite the fact that the punishmentswere discontinued. Furthermore, the behav-ioral disturbances were highly resistant tomost therapeutic attempts.

That the cats reacted in this way is notparticularly surprising because they were be-

ing unexpectedly punished for an instinctiveconsummatory response (Solomon, 1964).From the point of view being developed here,however, what is especially interesting is theprocedure that was the most effective in ulti-mately diminishing the symptoms of experi-mental neurosis. Some of Masserman's catswere initially trained to press a switch toactivate the signal that was followed by food(i.e., they had control over the presentationof food to themselves). When punishment wasintroduced at the mom'ent of feeding, thesecats still developed all the "neurotic" symp-toms, although in a somewhat milder form.More important is the fact that during ex-tinction (i.e., when punishment was discon-tinued), these cats showed by far the mostrapid return to normal behavior patterns.These results are interesting from our view-point because they indicate that when ananimal has prior experience with control overfood presentation, it seems to be "immunized"against the long-term, neurosis-inducing ef-fects of punishment. Control may serve bothto attenuate the effects of the punishmentper se and to help break up the neuroticsymptoms once they have been established.Similar conclusions are suggested by the ob-servations of Masserman and Pechtel (1953).

Masserman (1943) originally interpretedhis findings in psychodynamic terms, attrib-uting the neurotic behavior patterns to con-flict between approach (feeding) and avoid-ance (fear) motives. Recently, however, Mas-serman (1971) himself has offered a modifiedaccount that is similar to, though less for-malized than, the one developed here. Heconcluded that "the various forms of 'con-flict' . . . may be subsumed under a broaderetiological rubric: namely, that in each in-stance the organism apprehends a failure topredict and control events important to itswelfare" (1971, p. 9).

Wolpe

In an attempt to clarify certain aspects ofMasserman's work, Wolpe (1952, 1958) in-troduced an additional comparison group.Paralleling Masserman's procedure, cats inone condition were first trained to feed at abuzzer signal from a box and later subjected


to footshocks at the moment of feeding. Anaverage of four shocks was needed to com-pletely suppress feeding in the situation. Theother group of cats was simply given classicalfear-conditioning trials, in which a horn wasfollowed by footshock. This group received anaverage of 10-20 shocks over two sessions.Both groups subsequently showed signs ofexperimental neurosis, including generalizedanxiety inside and outside the experimentalsituation, activity-level changes, increasedstartle responses, anfl refusal to feed in theexperimental chamber even when very hun-gry. These effects persisted over many ses-sions despite the fact that no more shockswere given. Because essentially identical be-havior was observed in both groups, Wolpeexplained the development of experimentalneurosis as a simple example of fear condi-tioning, in contrast to the dynamic accountprovided by Masserman. Although moreshocks were given to Wolpe's simple fear-conditioning group, Smart (1965) confirmedWolpe's observations in an experiment thatequated the shocks received by the conflictand no-conflict groups.

Wolpe (1958) extended his theory to ac-count for all the examples of experimentalneurosis that have been discussed here. Heasserted that in all cases, fear or anxiety wasaroused and conditioned to situational cues,thus accounting for the persistence of thebehavioral disturbances even when the pre-cipitating conditions had been removed.Wolpe's theory concentrates on the internalstate of the animal (anxiety) and the condi-tioning of that state to neutral cues. Histreatment of the precipitating factors of anxi-ety is secondary (noxious or ambivalent stim-uli impinging on the organism) and somewhatpost hoc. For example, if difficult discrimi-nations had not produced neuroses, Wolpewould not have looked for evidence to arguethat ambivalent stimulation produces anxiety(e.g., his citation of Fonberg, 1956). In es-sence, any procedural manipulation that re-sulted in experimental neurosis would beassumed also to cause anxiety, often withoutany independent means of verifying that fact.For Wolpe, experimental neurosis is condi-tioned anxiety, more or less by definition.

Our approach differs from Wolpe's in thatwe emphasize the precipitating conditionsthat lead to experimental neurosis: Whenimportant life events become unpredictableor uncontrollable, or both, behavioral dis-turbances result that have sometimes beenlabelled experimental neurosis. The state ofthe organism induced by such manipulationsof controllability or predictability may some-times be what Wolpe labelled "anxiety," andwhen it is, we would expect that anxiety to beconditioned to the experimental situation. If,however, some other state, not easily char-acterized as anxiety, is induced (e.g., pas-sivity and depression), then we may also callthis experimental neurosis, whereas Wolpewould not. The advantages of our approachare twofold. First, it is more easily testablethan Wolpe's because the precipitating condi-tions can be operationalized. Second, it is notconcerned with whether the state of the or-ganism in every case of experimental neu-rosis can always be characterized as anxiety.

We now illustrate the testability of ourtheory with regard to Wolpe's own paradigmfor experimental neurosis. We have arguedthat predictable aversive events are consider-ably less aversive than unpredictable ones(e.g., Seligman, 1968). Thus, it is not im-mediately clear why Wolpe's cats who re-ceived classical fear-conditioning trials de-veloped generalized neurosis whereas Selig-man's rats who received classical fear condi-tioning did not. However, if we look at Selig-man's rats on their first 6 days of conditioning,we find that their behavior was as suppressedas that of the unpredictable group (i.e., theywere exhibiting a CER to the situation as awhole). Only on Day 7 did their CER start tobecome specific to the CS. This is what wouldbe expected by current models of Pavlovianconditioning (e.g., Rescorla & Wagner, 1972).Because Wolpe's cats received only 10-20fear-conditioning trials over only 2 days, it isnot surprising that their fear was conditionedto the situation as a whole rather than spe-cifically to the CS. Our prediction, then, isthat further CS-UCS pairings would havemade Wolpe's cats less generally neurotic (i.e.,their fear would have become specific to theCS) rather than more neurotic, as Wolpe


would predict.2 In other words, predictabilitycan only mitigate anxiety if the animal hashad a chance to learn that there is a reliablepredictor of the UCS.

Implications

We have shown that many of the behavioraleffects of exposure to unpredictable and/oruncontrollable shock are mirrored in the symp-toms of experimental neurosis—for example,cognitive deficits, agitation, passivity, distur-bance in feeding and in patterns of dominance(see especially Thomas & Dewald, 1977).These parallels suggest that the proceduresemployed for inducing experimental neurosismay be amenable to analysis in terms of thepredictability and controllability of importantenvironmental events. Our retrospective analy-sis of the classic studies performed by Pavlov,Gantt, Liddell, Masserman, and Wolpe, andtheir associates, suggests that these factorsdid play an important and perhaps centralrole in their procedures and in the outcomesthat were observed. In light of the wideranges of procedures employed to produce ex-perimental neurosis, the fact that two com-mon features can be distilled is particularlystriking. Our account seems especially com-pelling for the studies of Pavlov, Gantt, Mas-serman, and Wolpe. Liddell's work occasion-ally presents some difficulties, but even therewe have been able to discern elements of un-predictability and uncontrollability (especiallythe latter). We also noted that some of theseinvestigators themselves anticipated our ac-count by referring to problems of expectationsand restraint posed by their procedures.

Questions for Further Research

Our analysis raises as many questions as itsuggests answers. First, we are impressed bythe striking individual differences in subjects'reactions to any particular procedure used toinduce experimental neurosis. Some animalsbecome passive, but others become diffuselyagitated; still others develop specific defen-sive reactions of many kinds. Further, thePavlov and Liddell studies remind us thatsome animals break down under what appearsto be relatively moderate stress, whereas some

require extraordinary treatment. It is im-portant to remember that many animals donot develop experimental neurosis at all. Someof the relevant factors here probably relate toenduring temperamental features of the ani-mals. We certainly need further research onthe genetic-constitutional, as well as the ex-periential, factors that predispose an organismto react in a certain way to situations inwhich it has lost predictability and control-lability. Attempts to isolate the genetic fac-tors responsible for behavioral differences infear and avoidance conditioning have been re-ported by Broadhurst (1969), Katzev andMills (1974), and Gray (1971), among others,but their research has not yet dealt with theissues of predictability and controllability.Seligman (197S) and his associates, further-more, have speculated extensively on thoseaspects of experience, especially early in thecourse of development, that many immunizethe organism to the loss of controllability, butthis theory at present lacks specificity.

Still another issue highlighted by the experi-mental neurosis literature pertains to the rela-tionship between predictability and control-lability, and the ways in which the lack of onecan compound the effects of the lack of theother. In the experimental neurosis litera-ture, nearly all the paradigms are variants onclassical conditioning paradigms (with the ex-ception of Masserman's punishment proce-dure), and hence involve uncontrollable eventswith varying degrees of unpredictability. Theextent to which the effects of uncontrollabilityare compounded by these varying degrees ofunpredictability is not yet clear because fewstudies have independently manipulated pre-dictability of stimulus onset and controllabil-ity of stimulus offset. In one such study, using

2 Interestingly, Wolpe has data from one cat thattends to support our prediction. His Cat 14 (1958, p.54) was given extensive discriminative conditioningin the following paradigm: Food pellets preceded bya buzzer (CS—) were not followed by shock, where-as food pellets preceded by no buzzer (CS+) werefollowed by shock. Over 21 sessions the cat learnedthe discrimination and only showed signs of fearwhen pellets not preceded by a buzzer (CS+) weredropped into the box. By this time he did not showsigns of experimental neurosis, although in theearlier sessions there is some indication that he did.


a stress-induced ulceration measure, Weiss(1971) found signalled escapable shock to beleast stressful, unsignalled escapable and sig-nalled inescapable shock to be equally andsomewhat more stressful, and unsignalled in-escapable shock to be most stressful.

A third matter pertains to what might becalled the threshold for response to the lackof predictability and/or controllability. Wenoted earlier that punishment and fear condi-tioning—situations in which aversive stimula-tion is inherently uncontrollable—do not or-dinarily produce gross behavioral disturbancesof the kind observed by Masserman (1943)and Wolpe (19S8). Obviously some other fac-tors must contribute in important ways tothe production of experimental neurosis. Forexample, the punishment of a consummatoryresponse may be especially stressful for anorganism because in essence he loses a sub-stantial degree of control over a vital lifefunction. In addition, predictability and con-trollability may be especially salient featuresof an environment when aversive stimulationis intense, frequent, or prolonged, but notwhen it is mild or infrequent. Future researchshould attend more closely to differentiatingthose situations in which lack or loss of pre-diction and control matters from those inwhich these factors are of minimal importance.In one such recent attempt, Wortman andBrehm (197S) have argued that the initial re-sponse to loss of control is reactance or mo-tivational arousal. Repeated or prolonged ex-posure to the same uncontrollable events, how-ever, eventually results in the cognitive, affec-tive, and motivational deficits labelled learnedhelplessness by Seligman, Maier, and theircolleagues. Furthermore, the more importantthe uncontrollable outcome is to the subject,the more helpless he will eventually become(see Roth & Kubal, 1975, for recent empiricalsupport of this integration of reactance theorywith learned helplessness theory).

A fourth issue highlighted by our considera-tions of the experimental neurosis literaturepertains to the importance of lack versus lossof controllability and predictability. Most re-search reviewed in our discussion of these twoconcepts has emphasized the importance oflack of control or predictability. In fact, with

regard to controllability, Seligman (1975) hasargued that a prior history of control shouldimmunize against the effects of loss of con-trol. Intuitively, however, it seems obviousthat there will be cases in which loss of con-trol, given some prior history of control, willhave profound effects like those we have dis-cussed in this article. There may in fact besituations in which loss of control is morestressful than never having had it (Hanson,Larson, & Snowdon, 1976; Stroebel, 1969).With regard to predictability, we have indi-cated earlier that there seems to be a com-plete lack of research on the results of loss ofpredictability. No concept parallel to im-munization has been suggested for predicta-bility, and our analysis of Pavlov's andGantt's cases of experimental neurosis wouldlead us to expect that loss of predictabilityin an organism who once had it may some-times produce more profound disturbancesthan mere lack of predictability in an organ-ism who never had it.

Clinical Relevance oj Experimental NeurosisIn this article, we have intentionally ig-

nored the issue of whether the symptoms ofexperimental neurosis directly resemble thoseof neuroses seen in the psychological clinic.This matter has been dealt with by others(e.g., Abramson & Seligman, 1977; Broad-hurst, 1961; Hebb, 1947), who have generallyconcluded that the parallel between experi-mental and clinical neuroses should not bepressed too far. The reason for such reserva-tions does not stem from any specific evidencethat the symptoms are not parallel. Rather,such reservations derive from the fact thatfew systematic empirical comparisons betweenexperimental animal and human clinical neu-roses have ever been made. Within the frame-work of current approaches to animal modelsof human psychopathology (e.g., Abramson &Seligman, 1977; McKinney, 1974), it would,in principle, be possible to determine if ex-perimental neurosis is a good model of anyform of human psychopathology. Certainlyour review suggests that there are some im-portant commonalities between the sources ofexperimental neuroses and the factors knownto be important in the etiology and mainte-nance of certain forms of clinical psycho-pathology.


It does seem unlikely that all the cases ofexperimental neurosis resulting from the myr-iad procedures we have discussed here wouldall model one form of psychopathology. Someof the symptoms as described by the investi-gators resemble certain symptoms of anxiety—hypersensitivity, howling, rapid respiration,piloerection, muscular tension, mydriasis (e.g.,Wolpe, 1958). Other symptoms resemblesymptoms of depression—passivity, lethargy,smooth hair, anorexia (e.g., Thomas & De-wald, 1977). Interestingly, some animals seemto exhibit first the anxiety symptoms and laterthe depressive symptoms (e.g., Thomas & De-wald, 1977). Some investigators have sug-gested that excessive amounts of unpredicta-bility generally lead to anxiety, whereas ex-cessive amounts of uncontrollability generallylead to depression (e.g., Seligman, 1975). Butbecause lack of predictability and lack of con-trollability are intertwined in complex ways,this point of view suggests a distinction be-tween anxiety and depression that may beoversimplified. We note, for example, that anx-iety and depression often occur together, espe-cially in neurotics (e.g., Derogatis, Klerman,&Lipman, 1972; Mendels &Weinstein, 1972),and that prolonged anxiety states generallyend in depression (Freud, 1926/1959).

These considerations of predictability andcontrollability may allow future investigatorsto spell out some of the possible relationshipsbetween anxiety and depression in terms thatare more adequately operationalized thanthose used in the past. Environmental eventsmust in principle be either predictable or un-predictable and either controllable or uncon-trollable, generating four possible combina-tions of predictability and controllability.Moreover, an organism may often not be ableto find the correct coping response necessaryto gain control; hence, events that are inprinciple controllable may be perceived as un-controllable.3 This could occur either becausethe person may actually not see the relation-ship between the possible response and a fav-orable outcome or, alternatively, because hemay perceive the response-outcome relation-ship but perceive himself to be incapable ofperforming the response (Bandura, 1977).These three variables then—unpredictability,

veridical uncontrollability, and perceived (non-veridical) uncontrollability—may in fact gen-erate six possible "mixes" of anxiety and de-pression.

Conclusion

We obviously believe that experimental neu-rosis is more than a historical curiosity or anacademic puzzle. In the first place, it hasraised many interesting new questions aboutthe behavioral and cognitive effects of unpre-dictable and/or uncontrollable environmentalevents. Moreover, it seems that there aresome important similarities between experi-mental neurosis and human psychopathology.In this latter point we concur with Thomasand Dewald (1977), who have noted strikingparallels between experimental neurosis andlearned helplessness following exposure to un-controllable shock, which in turn has beenlinked to depression (Seligman, 1975). Theiremphasis has been on comparing symptomatol-ogy, associated brain mechanisms, and cure.However, an adequate laboratory model mustgo beyond these points of similarity and ex-plore etiological commonalities as well (Abram-son & Seligman, 1977; Seligman, 1975).

In this article we have tried to documenttwo threads that run through the experimen-tal neurosis literature—unpredictability anduncontrollability. These factors have also beenfound to be important elements underlyingcertain behavioral disorders that are observedclinically, It is our hope that this analysis willlead to further empirical attempts both tounderstand and to learn from the phenomenaof experimental neurosis.

3 Logically, the possibility also exists that uncon-trollable events are actually thought to be con-trollable (e.g., through superstitious learning). Thispossibility will not be dealt with here, because it isprobably not important in generating the kinds ofpsychopathological symptoms we deal with.

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Received April 11, 1977Revision received November 23, 1977

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