Some variables affecting conditioned suppression in humans

Some variables affecting conditioned suppression in humans

BEHAVIOR'I'ttEIIAPY(1971) 2, 554--559 Some Variables Affecting Conditioned Suppression in Humans GENE W. IlAND, HOWARD N. SLOANE, JR., a AND WILLIAM ...

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BEHAVIOR'I'ttEIIAPY(1971) 2, 554--559

Some Variables Affecting Conditioned Suppression in Humans GENE W. IlAND, HOWARD N. SLOANE, JR., a AND WILLIAM Il. DOBSON Universit~t o[ Utah and Veteran's Administration Hospital, Salt Lake City, Utah

An attempt was made with 20 adult male human subjects to produce the behavioral disruption demonstrated in animals and called conditioned suppression or the conditioned emotional response (CER). Various intensities of ac and dc electric shock were used, including maximum intensities which would maintain subjects' attendance at sessions. The preaversive stimuli and the shock were imposed upon lever pressing behavior maintained on VI Schedules of reinforcement and on FI-LH schedules. Animal research suggests that these schedules are highly sensitive to the CER effect. Parameters of the preaversive stimulus such as loudness, duration, and average interstimulus interval were selected which maximize the likelihood of obtaining suppressive effects with animals. No conditioned suppression was obtained. Until further clarification of the status of the CER in humans is available, attempts to describe human behavior in terms of "conditioned anxiety," viewed as analogous to the CER in animals, appears unwarranted. Estes and Skinner (1941) demonstrated the interruption of ongoing behavior by the presence of a CS previously paired with a noxious UCS. This phenomenon has been referred to classically as conditioned suppression or conditioned emotional response ( C E I l ) , following Brady and H u n t (1955). The importance of conditioned suppression is its use as an experimental analog of "anxiety." While ample evidence exists for this behavioral effect in lower animals (Estes & Skinner, 1941; Brady & Hunt, 1955; Brady & Conrad, 1960; Valenstein, 1959), only one reported study (Mulder, Lyon, &Pott, 1967) indicates even partial success in demonstrating the effects in humans. "Anxiety" is a construct which has typically been accorded a major role in the development and maintenance of behavior problems. Contemporary behavior therapy is no e x c e p t i o n ~ W o l p e (1969, p. 24) stated that " . . . there are very few neuroses which can be overcome without eliminating anxiety . . . . " However, the coneept of anxiety has m a n y ambiguous and poorly defined usages (English & English, 1958), most of which lack Requests for reprints should be sent to Howard N. Sloane, Jr., Bureau of Educational Research, 308 MBH, University of Utah, Salt Lake City, Utah 84112. 554

CONDITIONED SUPPRESSION IN HUIV~ANS

5*55

any operational definition (Marx, 1965). Many empirically oriented writers feel it has no experimental status ( Mandler & Kesson, 1965). Thus, the demonstration by researchers such as Brady and H u n t (1955) that the conditioned suppression procedure in animals produces a disruption of ongoing voluntary behavior and reflex behaviors such as crouching, "freezing," urination, and defecation seemed a boon. These are animal behaviors analogous to the changes many writers on disordered human behavior attribute to or define as "anxiety." Lundin (1961) specifically stated that " . . . the occasions for arousing anxiety in humans fit the general paradigm that we used for conditioning the operation at the animal l e v e l , . ." and this "general paradigm" is that for producing CER. Unfortunately, as pointed out earlier, a satisfactory demonstration of conditioned suppression in humans has not yet been reported. The purpose of the present research was to attempt further clarification of the parameters under which conditioned suppression might occur in humans.

Subjects and Apparatus Subjects were 20 male veterans from the alcoholic ward at the Veteran's Administration Hospital, Salt Lake City, Utah. None of the subjects was on any known medication that would affect his sensitivity to the aversive stimulus ( e.g., phenothiazines). Shock was delivered to subjects via forearm electrodes from one of two sources: A Grass S-4 stimulator generating dc pulse trains or a Foringer shock power supply (Model 1154M2) generating isolated alternating current. The experimental chamber and manipulanda were similar to that described b y Lindsley (1956). Experimental contingencies and recording were automatically controlled. EXPERIMENT 1

Procedure For each subiect, phmger pulling was established on a VI-3' schedule of reinforcement in daily sessions of 30 rain. The tokens used as reinforcers could be exchanged for money, candy, or cigarettes. When stable rates were obtained, two 750 Hz tones of 30-sec duration were randomly presented through a concealed loudspeaker during each session. The tone was presented alone until stable rates were achieved (carried from 5 to 17 sessions). In consecutive sessions after the rates stabilized, tone termination was made coincident with a brief electric shock delivered through forearm electrodes. The suppression procedure was programmed independently of the reinforcement schedule. With four subjects, the shock intensity remained at 1.7 mA, 180 V dc, throughout the experiment; three other subjects experienced one increase in shock intensity to

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7.5 mA, 180 V de; tile remaining three subjects experienced four levels of shock intensity: 1.7, 7.5, and 12.4 mA at 180 V de, and 3.5 mA at 300 V ac.:

Results and Discussion Results are reported in terms of the suppression ratio s = R--/R-}-, where R - - = the mean response rate in the absence of the CS, and R-}- = the response rate during CS. S values greater than 1.0 indicate suppression; an s value of 1.0 indicates no change; s values less than 1.0 indicate facilitation. The s ratios for the last five periods in each condition are summarized in Table 1. The failure to obtain conditioned suppression is partly in agreement with Kanfer (1958) and Sachs and May (1967). While the results of this experiment indicate a slight facilitation effect in some subjects, these increases in responding are neither systematic nor significant. Blackman (1968) indicated that suppression and facilitation occur, in part, as a function of the baseline schedule. To maximize the probability of obtaining conditioned suppression with humans, Experiment 2 was conducted utilizing an FI-LH schedule (reported by Blackman to be highly sensitive to suppression). In addition, the maximum shock inTABLE 1 Mean S Ratios for Last Five Sessions Under Each Condition in Experiment 1 (VI-3' Schedule) Experimental condition

Subject number

Baseline (tone--no shock)

Shock (180 Vdc 1.7 mA)

1 2 3 4 5 6 7 8 9 10

.9352 1.0428 ,9322 1.4218 .9638 .9112 .9510 .9595 .8992 .9632

.9166 .9456 .8408 .9780 1.1716 .8696 .9604 .9552 1.5150 .9928

Shock (180 Shock (180 Shock (300 Vdc 7.5 mA) Vdc 12.4 mA) Vac 3.5 mA)

.9738 .6168 .9482 .9532 .9514 .9342

.9550 .6400 .9460

.8584 .9492

a The subject left the experimental enclosure after two shocks at this level and did not return for additional scheduled sessions. 2 All subjects reported that the ac shock was much more aversive than the highest dc intensity.

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tensity that would maintain subiects' attendance at experimental sessions was used. EXPERIMENT 2

Procedure The procedure was the same as that in Experiment 1, except that the reinforcement schedule used was FI-90LH-1, and, that after 50 CS-UCS pairings, the CS was presented alone for 10 sessions (extinction). Shock intensity was held constant at 3.5 mA, 300 V ac.

Results and Discussion S ratios for the last five sessions under the experimental condition and on extinction are presented in Table 2. 3 The s ratios do not differ significantly between baseline and the experimental condition or from the experinaental condition to extinction, Brief sessions using college students as subjects replicated these findings. The extreme difficulty encountered in attempting to demonstrate experimentally the suppression phenomenon with h u m a n subjects is perhaps indicative of the problems one must contend with in attempting to equate variables which may not be equal, H. M. Johnson (1928-1932) has referred to this as "equivocation"--calling two things equal, perhaps even identical, because they have the same name. Animal studies on conditioned suppression typically used f o o d - - a primary reinforcer--and specify operationally the conditions of deprivaTABLE 2 Mean S Ratios for Last Five Sessions Under Each Condition in Experiment 2 (FI-90 LH-1 Schedule) Experimental condition Subject number

Baseline (tone--no shock)

Shock (300 Vac 3.5 mA)

Extinction

11 12 13 14 15 16

1.007 .8802 .9774 ,9890 .9642 .9512

.9702 1.0386 .9790 ,9578 1.0444 .9684

.9830 .9678 .9693 .9558 .9705~ .9872

a The subject was discharged from the hospital after completing two sessions on ex tinction--mean s ratio shown is the average of those two sessions. 3The four subjects whose data are not reported in Table 2 did not complete enough experimental sessions to be included in the experiment.

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tion. Consistency among animals is not difficult to achieve. Human studies, however, most often utilize secondary reinforcers--commonly money. Even though money is often a strong generalized reinforcer, it is difficult to equate it with food given to a rat who is at 80% FFW. The reinforcing value of money for a given subject can be determined only experimentally and, most likely, varies greatly from subject to subject as well as from time to time for a given subject. While electric shock seems to be universally aversive, human subjects generally have more alternative responses available to them than the rat. All of our subjects, for example, refused to return after one session with a shock intensity of 4.0 mA at 300V ac. Mulder et al. (1987) somewhat corrected for this with the "heavy baseline" technique of increased reinforcement. Even though their subjects were receiving approximately $10 per hour session, only 16 of 25 completed the experiment and suppression was found in only four of these subjects. (Comparison is difficult since Mulder et al., failed to report some of the parameters of the aversive stimulus. ) Another variable reportedly affecting suppression is the conditioning history of the organism. Herrnstein and Sidman (1958), for example, found that monkeys previously trained on an avoidance schedule exhibited facilitation rather than suppression during the CS. The conditioning history of human subjects is largely an unknown variable which must be dealt with by imaginative experimental designs and increased laboratory rigor, Unfortunately, history is sometimes difficult to correct for. Even when it is not, one's "correctional procedure" may occasionally obscure the phenomenon under investigation. Several possibilities thus exist to "explain" the failure to obtain conditioned suppression in humans. Demonstration of conditioned suppression in human subjects comparable to the effect produced in animal subjects may require comparable experimental conditions. It is possible that the phenomenon may be species-specific, and not exist in humans although, like most "negative proofs," this cannot be established definitively, and would be foolish to accept barring extensive parametric studies using varied procedures. In any case, it currently appears unwarranted to describe certain human behavior as a function of "conditioned anxiety" on the assumption that "conditioned anxiety" is a demonstrated human phenomenon equivalent to the CER in animals. REFERENCES BLACKblAN, D.

Conditioned suppression or facilitation as a function of the behavioral baseline. Journal o] the Experimental Analysis of Behavior, 1968, 11, 53--61. BI~ADY, J. V., & CONn~,D,D. G. Some effects of limbie-system self-stimulation upon

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conditioned emotional behavior. ]ournal o[ Comparative and Physiological Psychology, 1960, 53, 128-137. BRADY, J. V., & HUNT, H. F. An experimental approach to the analysis of emotional behavior. Journal o[ Psychology, 1955, 40, 313-324. ENCLISH, H. B., & ENCLISrI, A. C. A comprehensive dictionary of psychological and psychoanalgtic terms. New York: Longmans Green, 1958. ESTES, W. K., & SKIZ~'NEa,B. F. Some quantitative properties of anxiety. Journal o[ Experimental Psychology, 1941, 29, 390-400. HErmNsTEIN, R. J., & SIDMAN, M. Avoidance conditioning as a factor in the effects of unavoidable shocks on a food reinforced behavior. Journal o[ Comparative and Ph{lsiologieal Psychology, 1958, 5I, 380-385. JOHNSO~r, H. M. Some fallacies underlying the use of psychological tests. Psychological Review, 1928, 35, 328-337. JOHNSON, H. M. Some follies of "emancipated psychology." Psychological Review, 1932, 39, 293-323. KANFER, R. H. Effect of a warning signal preceding a noxious stimulus on verbal rate and heart rate. Journal oJ Experimental Psychology, 1958, 55, 73-79. LINDSLEY, O. R. Operant conditioning methods applied to research in chronic schizophrenia. Psychiatric Research Reports, 1956, 5, 118-139. LuNm~, R. W. Personality: an experimental approach. New York: MacMillan, 1961. MANBLER, G., & K~SSEN, W. The Language o[ Psychology. New York: Wiley, 1964. MARx, M. H. Theories in contemporary psychology. New York: MacMillan, 1964. MULDER, D. W., LYON, D. 0., & POTT, E. W. Conditioned suppression in hmnans. Paper presented at the Midwestern Psychological Association, May 6, 1967, Chicago, Illinois. SACHS, D. A., & MAY, J. G., Jn. Conditional emotional response with hmnans: The effect of a variable interstimulus interval using a trace conditioning paradigm. Psychonomic Science, 1967, 9, 343-344. VALENSTEIN, E. S. The effect of reserpine on the conditioned emotional response in the guinea pig. Journal o~ the Experimental Analysis of Behavior, 1959, 2, 219225. WOLd'E, J. The practice of behavior therapy. New York: Pergamon, 1969.