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The effectiveness of electric shock and foul odor as unconditioned stimuli in classical aversive conditioning
B&v.
Res. & Therapy. 1977. Vol. 15. pp. 167-175. Pegamon
Press. Prmted m Great Britam
THE EFFECTIVENESS OF ELECTRIC SHOCK AND FOUL ODOR AS UNCONDITIONED STIMULI IN CLASSICAL AVERSIVE CONDITIONING* CAROL J. BUSCH~ and IAN M. EVANS Psychology Department, University of Hawaii, Honoluht, Hawaii 96822, U.S.A. (Received 13 May 1976) Summary-in a partial replication of an earlier study, eighty undergraduate volunteers were assigned to the eight cells of a three between- and two within-group experimental design. One factor was the nature of the UCS-faradic shock or a carefully-timed blast of pyridine vapor; the second factor was the UCS contingency-the UCS being contingent upon the CS or randomly interspersed; the third factor was the nature of the CS-all CSs were compounds of colored, flavored liquids, with the discriminable dimension being either color or taste. The two within-subjects factors were the successive presentation of either the CS+- of the CS- over trials in a standard classical conditioning format. The outcome measures were sip-size, order of preference, and semantic differential ratings. It was found that the foul odor UCS resulted in no aversive conditioning with either color or taste cues. Where shock was the UCS, color, but not taste, became aversive. While lending no direct support to cue-appropriateness concepts, the results reveal the complexity of cue utilization in human aversive conditioning.
In a previous communication (Evans and Busch, 1974), we reported the findings from a study of classical aversive conditioning with colored, flavored liquids. The impetus for that investigation came from a suggestion by Wilson and Davison (1969) that shock would be an ineffective UCS when the CS was the taste of a given substance. Their position was based on animal studies purportedly demonstrating some kind of “cue specificity” when establishing aversions to edible substances. Wilson and Davison argued the significance of this body of animal research for aversion therapy; the refrain has since been taken up by others (Elkins, 1974; Garb and Stunkard, 1974; Revusky, 1973) although neither the original animal findings (see Bitterman, 1975), nor their relevance to humans (Evans, 1976; Evans and Busch, 1974) are very credible. Despite doubts regarding the propitiousness of the cue specificity idea, more detailed und~rs~nding of mechanisms underlying aversion therapy is badly needed (Hallam et al., 1972) and our first study did contain certain flaws. Firstly, although a generally adequate discrimination control procedure was used, it could not control for change resulting from simple repetition of the CS, particularly in an unbalanced design. Secondly, the real interest for behavior therapy is the comparison of UC%, and only one UCS, electric shock, was used in the first experiment. To overcome these limitations a second study was designed in which a foul odor WCS was introduced so that its effectiveness might be compared to an electric shock UCS; this paper reports the findings from that second study. METHOD
The Ss were 40 male and 40 female Oriental undergraduate volunteers, divided into four experimental and four control groups in such a way as to achieve an equal number of males and females in each group. * Equipment used in this study was provided by a grant from the University of Hawaii Research Council, which is acknowledged with thanks. The authors are grateful to Rory Cahoon and Dorothy Kagehiro for their assistance in conducting the experiment. Requests for reprints should be sent to Ian M. Evans. t Now at the Addiction Research Unit, Institute of Psychiatry, London. 167 II.R.T. 15.2-n
CAROL J. BUSCH and IAN M. EVANS
168
Apparatus
and stimuli
The two substances used as the primary gustatory stimuli were a dilute solution of citric acid (l.Og anhydrous H3CsH507 per liter of water), and a dilute solution of table salt (3.0 g NaCl per liter of water). The two primary visual stimuli were red and orange colored solutions, the colors being obtained by mixing tasteless commercial vegetable dyes with water. In the preference and rating tests given before and after the conditioning trials. the two additional gustatory stimuli were a dilute solution of sugar (12.0 g granulated white sugar per liter of water), and a dilute solution of sodium bicarbonate (6.0 g NaHCO, per liter of water). The two additional visual stimuli were blue and green colored solutions, made with vegetable dyes as above. The four flavored stimuli were all of sufficiently weak concentrations that they were colorless and odorless. The four visual stimuli were simply observed and not tasted by the S during the pre and post tests. For the conditioning trials, 34 ml of each of the two CS solutions used were measured into white plastic cups with covers and arranged on trays in the manner previously described (Evans and Busch, 1974). For the preference tests, the four flavored and four colored solutions were presented in cups identical to those used in the conditioning trials. These were placed in two holders each containing twelve numbered wells, with the first well being additionally labeled “very positive” and the last well being labeled “very negative.” One holder contained the four flavored substances: salt. citric acid, soda and sugar; the other holder contained the four colored substances: red. orange, blue and green. These cups were arranged in the middle of the two holders in random order for both the pre and post test. Half the Ss within each group rated the colored fluids prior to the flavored in the pre test while the other half rated the flavored fluids first. This order was reversed for all Ss in the post test. The semantic differential used for rating the fluids before and after conditioning contained nine adjectival pairs. Three pairs correlated highly with the evaluative dimension and three pairs, which were used as fillers and not analyzed, correlated with the activity dimension (Osgood et al., 1957). The last three pairs correlated with an anxiety dimension (O’Donnell, 1973). These nine pairs were arranged in a different order for the pre test and the post test, all Ss receiving the identical order. The experimental room, the control equipment and recording methods were all similar to those used in the earlier study. Briefly, the subject sat in a room separated from the experimenter and the equipment by a one-way mirror; communication was by intercom. The S sat in front of a table in a standard classroom chair with a right-hand writing ledge. During conditioning a cuspidor was placed on this ledge. and a wastebasket was placed on the S’s left. Shock was delivered by a constant current device through copper disc electrodes placed in the manner previously described. The major addition to this study was the use of an unpleasant smell as a UCS, pyridine (C,H,N). a foul, gassy smelling chemical obtained from the distillation of coal tar. Air was pumped from a compressor into a single-vented flask containing the pyridine by means of a glass tube inserted through the bung in the neck of the flask and extending almost to the level of the pyridine. The difference in pressure between the atmosphere and the flask was maintained at 124 mm Hg as measured on a mercury manometer. The air-vapor mixture in the flask was led by means of a l/4-in. rubber tube about 8 ft long to a solenoid valve controlled by an interval timer. The valve was located immediately behind the S’s head; its operation was silent, as it had been designed for eyelid conditioning studies. A short (18-in.) length of plastic tube led from the valve to the S’s nose, where it was inserted l/2-in. into the S’s left nostril by means of a removable surgical-rubber tip. To secure the tube in that position, it was threaded through two loops attached to an elasticized terry-cloth band stretched around the S’s head and upper lip. To ensure that between trials pyridine vapor remaining in the tube between the valve and the nostril could not further stimulate the S, a continuous stream of fresh air passed along the final length of tubing at all times. This was done by means of a second compressor, equipped with a controllable reducing valve which
The effectiveness
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shock and foul odor
169
was attached to one arm of a Y valve. The other arm of the Y was attached to the solenoid valve and the stem of the Y constituted the tube to the S’s nose. The reducing valve was adjusted so that a gentle, detectable flow of air passed into the S’s nostril. All s’s, regardless of group, received this form of stimulation. A powerful exhaust fan located in the wall nearest to the S drew air out of the experimental chamber. In addition, a few drops of Oil of Wintergreen (methyl salicylate) were placed in an open container in the experimental chamber since its aromatic odor neutralizes pyridine. There was also a white-noise generator to mask general noise in the building, and both this and the exhaust fan were in operation continuously throughout the session. Design and procedure
The procedure used in each trial for the two visual experimental groups (Group 1 and Group 5) was as follows. E pressed Button 1 which activated an event marker and produced a standard 0.5~set tone (Tone 1) in the experimental room, the S’s signal to remove the lid off the cup. When the S raised the lid off the cup, E pressed Button 2 which both activated another channel of the event recorder and started a timer. Exactly 2.5 set later a OS-set aversive UC’S (shock or smell) was automatically delivered to the S. Four set later, Tone 2 sounded in the experimental room, signalling to the S to pick up the cup. At the moment that the cup touched the S’s lips, E pressed Button 3. This both activated a channel of the event recorder and started a timer. Seven seconds later Tone 3 automatically sounded in the experimental chamber, signalling to the S to spit out the fluid into the cuspidor. The two visual control groups (Group 3 and Group 7) experienced the identical sequence with the major exception that the UCS was delivered randomly during the 28 trials and inter-trial intervals, rather than 2.5 set after removing the lid from the cup. The two taste experimental groups (Group 2 and Group 6) experienced a similar sequence as the two visual experimental groups with the following major exception: the UCS was delivered automatically 2.5 set after the cup reached the S’s lips instead of 2.5 set after the lid came off the cup. Again, the two taste control groups (Group 4 and Group 8) experienced the identical procedure with the exception that the UCS was delivered on a random basis. The decision to present the UCS 2.5 set after presentation of the CS+ was to provide sufficient time for the visual Ss to remove the lid of the cup, throw it in the basket and return their gaze to the cup prior to onset of the UCS. This CS-UCS interval also gave the taste Ss ample time to discriminate clearly the taste of the CS+ prior to experiencing the UCS. The 4-set delay after onset of the UCS was primarily to provide sufficient time for the odor to dissipate for the visual groups, thus reducing the possibility that odor was also being paired with taste, the irrelevant cue for these Ss. The fact that the visual groups continued to see the color of the fluids after the 7-set interval (the short period between Tone 2 signalling pick up of the cup and sipping), whereas the taste groups spat out the fluid immediately after the ‘I-set interval was one unavoidable difference between taste and color groups. However, it was surmised that aftertastes of the CS liquids would linger in the taste S’s mouths for a few seconds after spitting, thus reducing this difference. It will also be seen that for the taste groups the visual cue preceded the relevant taste stimulus, whereas for the visual groups the taste cue followed the visual: at least, however, the CS-UCS interval was the same for the two conditions. Conditioning was carried out according to a standard classical discrimination procedure: two stimuli were presented in random sequence, one stimulus (the CS+) being followed by an aversive UCS, the other stimulus (CS-) not being followed by the UCS. For Groups 1, 2, 3 and 4, the UCS was electric shock; for Groups 5, 6, 7 and 8, the UCS was the unpleasant odor. Groups 1, 2, 5 and 6 were the four experimental groups, receiving the UCS contingent on presentation of the CS+. Groups 3, 4, 7
170
CAROLJ. BUSCHand
IAN
M. EVANS
Table 1. Factorial design UCS Contingency
CS
Ss
Discrimination CS* CS,
Color
12 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
12 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Color
8 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
8 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Color
12 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
12 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Color
8 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
8 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Group
Contingent
Shock
Random
Contingent
Smell
Random
and 8 were presented with the same number of UCS as the experimental groups but received these on a random basis. The design is summarized in Table 1. The stimuli used in conditioning were presented as a visual-gustatory compound for all Ss, but for Groups 1, 3, 5 and 7, the only discriminable difference between the CS+ and the CS- was a visual cue (red vs orange), whereas for Groups 2, 4, 6 and 8, the only discriminable difference was the taste of the stimuli (citric acid vs salt). All groups were balanced with respect to which color or which taste was the CS + and which the CS - . Each S received a total of 28 stimulus presentations (trials): two presentations of the CS+ unpaired with the UCS were followed by 13 trials each of the CS + and CS - . The conditioning was terminated before reaching the last two cups on the tray in order to reduce any effects due to relief. Ss participated in the experiment knowing only that the intent of the study was to improve current methods of treating alcoholics, that it involved electric shock or an unpleasant odor, and that no alcoholic beverage would be used. The S was seated in the experimental room in front of two holders, one containing the four flavored liquids and the other containing the four colored liquids. The S was then instructed to taste the flavored liquids and rate each one on the semantic differential forms in front of him. The tastes were identified by number only. The S was then instructed to rank order these four cups, placing them according to his preference in any four
The effectiveness
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shock
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171
of the 12 numbered wells in the holder. The same procedure was followed for the colored liquids with the exception that the S looked at these rather than tasted them. Upon completion of the above, E removed the holders and semantic differential forms and prepared the Ss for conditioning. All Ss, regardless of which UCS they were to receive, had the electrodes strapped to their arms. All Ss also had the band placed around their heads and the tube inserted into their left nostril, which provided a gentle steady flow of air directly into the nose. This was to control for any unpleasant effects caused by the apparatus rather than the UCS per se. The E then returned to the control room and adjusted the shock level for those Ss assigned to the shock UCS groups. These Ss received a total of three shocks in increasing intensity and were asked after each one to rate it on a lo-point scale of severity (1 was very mild, 10 was very unpleasant). The typical shock level selected was 0.7 mA AC (R.M.S.) and the range was from 0.3 to 1.0 mA. The mean rating was 7.81 and the range was 4 to 10. Those Ss assigned to the smell UCS groups also received three puffs of the pyridine and were asked to rate each puff on the same lo-point scale. The E had no way of adjusting the intensity of the odor but this procedure was followed, nonetheless, with the smell groups in order to equate their experience with the UCS with that of the shock groups. The mean rating was 7.80 and the range was from 3 to 10. The conditioning procedure itself has already been described. After the conditioning trials, E returned to the experimental room, removed the apparatus and repeated the preference rankings. The S then completed a brief questionnaire regarding perceived purpose of the experiment, and was dismissed. Feedback regarding the true purpose of the experiment was given at a later date.
RESULTS The dependent measures in this study were slightly different from those of the earlier investigation. The free-drinking test used before seemed unsound and was dropped. Three of the four performance measures were no longer appropriate for the modified design: response latency, as the Ss had to reach more varied distances; cup-to-lip time, as the taste groups could not tell which substance they were raising to their lips until they had tasted it; duration, as spit-out time in this study was regulated. The semantic differential was broken down into two dimensions: evaluative, as before, and anxiety. The ranking of the CSs with other stimuli was retained in modified form. Altogether, then, there were five dependent variables, each of which will be discussed in turn. The data were explored by means of analyses of variance and covariance; where individual comparisons between means are reported, significance was determined by Duncan’s New Multiple Range Test. Sip size
These data were averaged over four trial blocks. The first block contained the two test trials (CS+ without the UCS). and the first two conditioning trials (which were both CS - trials), and was therefore common to both CS+ and CS - performance curves. The second block contained the 2nd, 3rd, 4th and 5th presentation of the CS+ (for the CSt curve) and the 3rd, 4th and 5th presentation of the CS- (for the CScurve). The third block contained the 6th, 7th, 8th and 9th presentation of the CS+ and of the CS-. The final block contained the lOth, llth, 12th and 13th presentation of the CS+ and of the CS-. An analysis of covariance was then performed with the scores on the first trial block being the covariate for the within-subject analysis. It was expected that the size of the CS+ sips would be smaller than the CS- sips, but only for the contingent UCS groups (with the random groups there in no CS+/CSdistinction). The contingency/CS interaction however, proved to be non-significant (F = 1.83, df = 1,72, p > 0.10). It might also be expected that there would have been a greater decrease in sip size across trials for the groups that had contingent UCSs,
CAROL J. BUSCH and IAN M.
172
EVANS
but that interaction also failed to reach significance (F = 0.15, df= 2,144, p > 0.10). Individual comparisons among group means showed that only Group 1 showed a significant (p < 0.05) difference between CS+ and CS- sip sizes over Blocks 2, 3, and 4 of the conditioning trials. Visual inspection of the data revealed one other striking effect. Whereas all the groups receiving shock as the UCS decreased their sip sizes over trials. three of the four smell UCS groups increased sip-size across trials. Based on the subjective experiences of the authors, it is believed that the pyridine stimulated taste receptors and that larger sips helped wash away that unpleasant sensation. If this speculation is correct. it helps explain the differences between the present and the previous findings on this measure and shows the difficulties in establishing an unobtrusive behavioral measure that will be consistently appropriate. Semantic diflerential: evaluative scale
Figure 1 shows the group mean scores on the evaluative scale for the CS+ and CS- before and after conditioning. Since each S’s score was obtained by totalling his rating of three adjectival pairs correlating with the evaluative dimension, the maximum “pleasant” rating that could be obtained was 3, and the maximum “unpleasant” rating was 21. In the analysis of variance the main pre/post effect was significant (F = 14.10. df = 1,72, p < O.OOl), as was the interaction of pre/post by CS (F = 9.05, df= 1,72, p < 0.01) and the interaction between pre/post, CS, and contingency (F = 4.01, df= 1,72, p < 0.05). An examination of the means for the individual groups revealed that Group l’s postconditioning rating of the CS+ was significantly more negative than the pre-conditionUCS
I
Shock
Contingent
Random Taste
Color
Color UCS
Smell
L
Contfngent
COlOr
Taste
Taste
Color
Random
’
L
Taste
Fig. 1. Mean scores on the Evaluative scale of the Semantic Differential before and after conditioning trials. The higher the column, the more unpleasant the CS was rated. (Maximum negative rating = 21).
The effectiveness
of electric
shock
173
and foul odor
UCS Shock l5-
2 a f
lo-
5.
cst
c5+ cs-
cs-
cs,
cs2
Contmgent Color
CS,
cs2
Random Toste
Color
UCS
Taste
Smell E+ avlor E
5-
Contingent Color
Rondom Toste
Color
Taste
Fig. 2. Mean scores on the Anxiety scale of the Semantic Differential before and after conditioning trials. The lower the column, the more anxious the CS was rated. (Maximum anxiety rating = 3; minimum anxiety rating = 21).
ing rating (p < 0.05). The only other group to show a significant pre-post change in rating was Group 3 (Shock/Random/Color-again this was in the expected direction as these control Ss rated both CS, and CS2 more negatively after conditioning (p < 0.05). It can also be seen from Fig. 1 that the Ss consistently rated colored stimuli more (F = 38.33, positively than taste stimuli both before and after conditioning df = 1,72, p
diferential:
anxiety
scale
Figure 2 shows the group mean scores on the anxiety scale for the CS+ and CSbefore and after conditioning. The maximum anxiety score that could be obtained was 3 and the maximum “calmness” score possible was 21. Although the overall pre/post effect was not significant (F = 2.78, df= 1,72, p > O.lO), the UCS by contingency by CS by discrimination by pre/post was significant (F = 5.31, df = 1,72, p < 0.05). Comparisons of group means indicated that only one group showed a significant difference in pre/post ratings for CS+ and that was Group l-after conditioning the CS+ was rated as more anxious. None of the other pre/post changes, in any direction, were significant. The changes on the anxiety scale were thus smaller and fewer than on the evaluative scale which may indicate that the UCSs affective properties were more in the nature of discomfort than of fear. Rank order
In the previous report, rank order differences were calculated; however in this study, there were 12 possible positions and only 4 substances to be ranked, so absolute rank
CAROL J. BUSCH and IAN M. EVANS
174
UCS
cs+
cs-
Color
Shack
cst csContingent Taste
UCS
cs,
cs2
Color
Fig. 3. Mean ranking
cs2
Taste
Smell
_
Conhngent
Color
cs, Random
c
Random Taste
Color
before and after conditioning. The higher the column, the ranking. (Maximum negative ranking = 12).
Taste
the more
negative
positions were the data analyzed. The mean rankings for each group before and after conditioning are depicted in Fig. 3. Analysis of variance of these means showed that there was a significant main effect due to nature of the CS in which the taste stimuli were ranked more negatively than the color stimuli (F = 16.57, df= 1,72, p < 0.001). There was also a significant pre/post main effect (F = 11.17, df = 1,72, p < 0.01) and a significant interaction between pre/post and the nature of the CS: rankings tended to become more negative when the stimulus ranked was a color, and to remain unchanged when the stimulus ranked was a taste (F = 17.93, df= 1,72, p < 0.001). The easiest way to obtain a picture of theses results is by the pattern of individual mean differences that reached significance: significant individual pre/post differences were found only with Group 1 (in which the CS+ was ranked more negatively after conditioning), and with Group 3 (in which both CSs were ranked more negatively after conditioning). These findings directly parallel the findings with the evaluate dimension of the semantic differential. DISCUSSION
The most striking finding of this study was that saturated pyridine vapor blasted up the nostrils of the Ss did not prove to be an effective UCS whether the CS was a visual or gustatory cue. There are a variety of possible reasons for this failure whose validity only future research can determine. One possibility is that the pyridine was not sufficiently aversive. This seems unlikely as the Ss gave equivalent ratings to it and the shock in test trials, and habituation to its noxious properties appeared less than is the usual case with shock-Ss reported the smell UC’S as being increasingly unpleasant. The pyridine blast might have been avoidable to some extent; if the Ss
The effectiveness
of electric
shock
and foul odor
175
had held their breaths or breathed out hard through their noses, they might have been able to reduce significantly the discomfort, although the way the apparatus was arranged they would have received the stimulus eventually. Time relationships between the CS and UCS were also conceivably influenced by the aftertaste of the pyridine. In any event, while disrupted time relationships might have reduced the CS +/CS - discrimination, overall pre/post differences should still have been in evidence. No such changes were seen in the present study and pyridine does not, therefore, seem to be a promising stimulus for applied aversive conditioning. More prolonged trials or longer UCS durations could be harmful to the subject as pyridine is toxic. A second feature of the study was the failure to find conditioning to taste CSs with either shock or foul smell as the UCS. Thus a finding of the previous study was not replicated with what we consider to be an improved design. We would caution, however, against any “biological preparedness” interpretation until much more obvious factors have been excluded. In our attempt to make the taste CSs less aversive to begin with, weak concentrations were used, which may have been difficult for some Ss to discriminate. Further, although we also made the color CSs less attractive (using orange and red solutions which tend to be disliked by Ss) we were still dogged by significant starting differences between color and taste stimuli as in the previous study on the evaluative scale. Fortunately this was not true of the semantic differential anxiety ratings. A third point to notice is that while we tried to keep CS-UCS intervals constant in this study, there is an inevitable difference in CS-UCS relationships when the CS is a compound with either color or taste the crucial element. If the results were to be summarized one could say that with color CSs and shock UCSs, a small but statistically significant conditioning effect was found which was revealed by indirect behavioral and attitudinal measures. It is interesting that one of the control groups (Group 3) appeared to show a “conditioning” effect; we do not feel that this invalidates the conditioning procedure as this group showed change in both CSs-this can be accounted for by occasional chance pairings with the random shock or by the continued presence of cups of liquids as static apparatus cues (see Evans, 1976, for discussion pertinent to these two assumptions). None of the control groups fully eliminated the problem of experimental demand effects, although it is not clear why this variable did not operate on the unpleasant odor groups and taste/shock group. In general it must be admitted that this type of study does not provide an ideal link between pure laboratory conditioning studies and clinical aversion therapy, as it is analogous to neither-it lacks the direct CR measurement and masking procedures of the human conditioning experiment, and lacks the stimulus aversiveness justifiable in a clinical investigation. As mentioned elsewhere (Evans, 1976) it may be necessary to pursue this line of research in well-controlled treatment studies. REFERENCES BITTERMAN M. E. (1975) Issues in the comparative psychology of learning. In The Evolution of Brain und Behaaior in Vertebrates (Eds. R. B. MASTERTON. M. E. BITTERMAN, C. B. G. CAMPBELL and N. HOLTEN). Erlbaum. New York. ELKINS R. L. (1974) Conditioned flavor aversions to familiar tap water in rats: An adjustment with implications for aversion therapy treatment of alcoholism and obesity. J. ahnorm. Pspchol. 83. 41 l-417. EVANS I. M. (1976) Classical conditioning. In The Experimental and Theoretical Bases 01 Behmiour Therapy (Eds. M. P. FELDMAN and A. A. BROADHURST). Wiley, London. EVANS I. M. and BUSCH C. 1. (1974) The effectiveness of visual and gustatory conditioned stimuli in human classical aversive conditioning with electric shock. Brhar. Res and Therapy 12, 129-140. GARB J. L. and STUNKARD A. J. (1974) Taste aversions in man. Am. J. Psych& 131, 1204-1207. HALLAM R., RACHMAN S. and FALKOWSKI W. (1972) Subjective, attitudinal and physiological effects of electrical aversion therapy. Behm Res. and Therapy 10, l-13. O’DONNELL C. R. (1973) The measurement of anxiety and evaluative components in exam and speech concepts for males. J. c/in. Psxchol. 29, 326-327. OSWJOU C. E.. SKI G. J. and TANKENBAUM P. H. (1957) The Measurwe~~t of’ Mrunim~. University of Illinois Press, Urbana. REVUSKY S. (1973) Some laboratory paradigms for chemical aversion treatment of alcoholism. J. Behac. Ther. exp. Ps.whiat. 4, 15-17. WILSON G. T. and DAVIXIN G. C. (1969) Aversion techniques in behavior therapy: Some theoretical and metatheoretical considerations. J. consult. clin. Psychok 33, 327-329.
Res. & Therapy. 1977. Vol. 15. pp. 167-175. Pegamon
Press. Prmted m Great Britam
THE EFFECTIVENESS OF ELECTRIC SHOCK AND FOUL ODOR AS UNCONDITIONED STIMULI IN CLASSICAL AVERSIVE CONDITIONING* CAROL J. BUSCH~ and IAN M. EVANS Psychology Department, University of Hawaii, Honoluht, Hawaii 96822, U.S.A. (Received 13 May 1976) Summary-in a partial replication of an earlier study, eighty undergraduate volunteers were assigned to the eight cells of a three between- and two within-group experimental design. One factor was the nature of the UCS-faradic shock or a carefully-timed blast of pyridine vapor; the second factor was the UCS contingency-the UCS being contingent upon the CS or randomly interspersed; the third factor was the nature of the CS-all CSs were compounds of colored, flavored liquids, with the discriminable dimension being either color or taste. The two within-subjects factors were the successive presentation of either the CS+- of the CS- over trials in a standard classical conditioning format. The outcome measures were sip-size, order of preference, and semantic differential ratings. It was found that the foul odor UCS resulted in no aversive conditioning with either color or taste cues. Where shock was the UCS, color, but not taste, became aversive. While lending no direct support to cue-appropriateness concepts, the results reveal the complexity of cue utilization in human aversive conditioning.
In a previous communication (Evans and Busch, 1974), we reported the findings from a study of classical aversive conditioning with colored, flavored liquids. The impetus for that investigation came from a suggestion by Wilson and Davison (1969) that shock would be an ineffective UCS when the CS was the taste of a given substance. Their position was based on animal studies purportedly demonstrating some kind of “cue specificity” when establishing aversions to edible substances. Wilson and Davison argued the significance of this body of animal research for aversion therapy; the refrain has since been taken up by others (Elkins, 1974; Garb and Stunkard, 1974; Revusky, 1973) although neither the original animal findings (see Bitterman, 1975), nor their relevance to humans (Evans, 1976; Evans and Busch, 1974) are very credible. Despite doubts regarding the propitiousness of the cue specificity idea, more detailed und~rs~nding of mechanisms underlying aversion therapy is badly needed (Hallam et al., 1972) and our first study did contain certain flaws. Firstly, although a generally adequate discrimination control procedure was used, it could not control for change resulting from simple repetition of the CS, particularly in an unbalanced design. Secondly, the real interest for behavior therapy is the comparison of UC%, and only one UCS, electric shock, was used in the first experiment. To overcome these limitations a second study was designed in which a foul odor WCS was introduced so that its effectiveness might be compared to an electric shock UCS; this paper reports the findings from that second study. METHOD
The Ss were 40 male and 40 female Oriental undergraduate volunteers, divided into four experimental and four control groups in such a way as to achieve an equal number of males and females in each group. * Equipment used in this study was provided by a grant from the University of Hawaii Research Council, which is acknowledged with thanks. The authors are grateful to Rory Cahoon and Dorothy Kagehiro for their assistance in conducting the experiment. Requests for reprints should be sent to Ian M. Evans. t Now at the Addiction Research Unit, Institute of Psychiatry, London. 167 II.R.T. 15.2-n
CAROL J. BUSCH and IAN M. EVANS
168
Apparatus
and stimuli
The two substances used as the primary gustatory stimuli were a dilute solution of citric acid (l.Og anhydrous H3CsH507 per liter of water), and a dilute solution of table salt (3.0 g NaCl per liter of water). The two primary visual stimuli were red and orange colored solutions, the colors being obtained by mixing tasteless commercial vegetable dyes with water. In the preference and rating tests given before and after the conditioning trials. the two additional gustatory stimuli were a dilute solution of sugar (12.0 g granulated white sugar per liter of water), and a dilute solution of sodium bicarbonate (6.0 g NaHCO, per liter of water). The two additional visual stimuli were blue and green colored solutions, made with vegetable dyes as above. The four flavored stimuli were all of sufficiently weak concentrations that they were colorless and odorless. The four visual stimuli were simply observed and not tasted by the S during the pre and post tests. For the conditioning trials, 34 ml of each of the two CS solutions used were measured into white plastic cups with covers and arranged on trays in the manner previously described (Evans and Busch, 1974). For the preference tests, the four flavored and four colored solutions were presented in cups identical to those used in the conditioning trials. These were placed in two holders each containing twelve numbered wells, with the first well being additionally labeled “very positive” and the last well being labeled “very negative.” One holder contained the four flavored substances: salt. citric acid, soda and sugar; the other holder contained the four colored substances: red. orange, blue and green. These cups were arranged in the middle of the two holders in random order for both the pre and post test. Half the Ss within each group rated the colored fluids prior to the flavored in the pre test while the other half rated the flavored fluids first. This order was reversed for all Ss in the post test. The semantic differential used for rating the fluids before and after conditioning contained nine adjectival pairs. Three pairs correlated highly with the evaluative dimension and three pairs, which were used as fillers and not analyzed, correlated with the activity dimension (Osgood et al., 1957). The last three pairs correlated with an anxiety dimension (O’Donnell, 1973). These nine pairs were arranged in a different order for the pre test and the post test, all Ss receiving the identical order. The experimental room, the control equipment and recording methods were all similar to those used in the earlier study. Briefly, the subject sat in a room separated from the experimenter and the equipment by a one-way mirror; communication was by intercom. The S sat in front of a table in a standard classroom chair with a right-hand writing ledge. During conditioning a cuspidor was placed on this ledge. and a wastebasket was placed on the S’s left. Shock was delivered by a constant current device through copper disc electrodes placed in the manner previously described. The major addition to this study was the use of an unpleasant smell as a UCS, pyridine (C,H,N). a foul, gassy smelling chemical obtained from the distillation of coal tar. Air was pumped from a compressor into a single-vented flask containing the pyridine by means of a glass tube inserted through the bung in the neck of the flask and extending almost to the level of the pyridine. The difference in pressure between the atmosphere and the flask was maintained at 124 mm Hg as measured on a mercury manometer. The air-vapor mixture in the flask was led by means of a l/4-in. rubber tube about 8 ft long to a solenoid valve controlled by an interval timer. The valve was located immediately behind the S’s head; its operation was silent, as it had been designed for eyelid conditioning studies. A short (18-in.) length of plastic tube led from the valve to the S’s nose, where it was inserted l/2-in. into the S’s left nostril by means of a removable surgical-rubber tip. To secure the tube in that position, it was threaded through two loops attached to an elasticized terry-cloth band stretched around the S’s head and upper lip. To ensure that between trials pyridine vapor remaining in the tube between the valve and the nostril could not further stimulate the S, a continuous stream of fresh air passed along the final length of tubing at all times. This was done by means of a second compressor, equipped with a controllable reducing valve which
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was attached to one arm of a Y valve. The other arm of the Y was attached to the solenoid valve and the stem of the Y constituted the tube to the S’s nose. The reducing valve was adjusted so that a gentle, detectable flow of air passed into the S’s nostril. All s’s, regardless of group, received this form of stimulation. A powerful exhaust fan located in the wall nearest to the S drew air out of the experimental chamber. In addition, a few drops of Oil of Wintergreen (methyl salicylate) were placed in an open container in the experimental chamber since its aromatic odor neutralizes pyridine. There was also a white-noise generator to mask general noise in the building, and both this and the exhaust fan were in operation continuously throughout the session. Design and procedure
The procedure used in each trial for the two visual experimental groups (Group 1 and Group 5) was as follows. E pressed Button 1 which activated an event marker and produced a standard 0.5~set tone (Tone 1) in the experimental room, the S’s signal to remove the lid off the cup. When the S raised the lid off the cup, E pressed Button 2 which both activated another channel of the event recorder and started a timer. Exactly 2.5 set later a OS-set aversive UC’S (shock or smell) was automatically delivered to the S. Four set later, Tone 2 sounded in the experimental room, signalling to the S to pick up the cup. At the moment that the cup touched the S’s lips, E pressed Button 3. This both activated a channel of the event recorder and started a timer. Seven seconds later Tone 3 automatically sounded in the experimental chamber, signalling to the S to spit out the fluid into the cuspidor. The two visual control groups (Group 3 and Group 7) experienced the identical sequence with the major exception that the UCS was delivered randomly during the 28 trials and inter-trial intervals, rather than 2.5 set after removing the lid from the cup. The two taste experimental groups (Group 2 and Group 6) experienced a similar sequence as the two visual experimental groups with the following major exception: the UCS was delivered automatically 2.5 set after the cup reached the S’s lips instead of 2.5 set after the lid came off the cup. Again, the two taste control groups (Group 4 and Group 8) experienced the identical procedure with the exception that the UCS was delivered on a random basis. The decision to present the UCS 2.5 set after presentation of the CS+ was to provide sufficient time for the visual Ss to remove the lid of the cup, throw it in the basket and return their gaze to the cup prior to onset of the UCS. This CS-UCS interval also gave the taste Ss ample time to discriminate clearly the taste of the CS+ prior to experiencing the UCS. The 4-set delay after onset of the UCS was primarily to provide sufficient time for the odor to dissipate for the visual groups, thus reducing the possibility that odor was also being paired with taste, the irrelevant cue for these Ss. The fact that the visual groups continued to see the color of the fluids after the 7-set interval (the short period between Tone 2 signalling pick up of the cup and sipping), whereas the taste groups spat out the fluid immediately after the ‘I-set interval was one unavoidable difference between taste and color groups. However, it was surmised that aftertastes of the CS liquids would linger in the taste S’s mouths for a few seconds after spitting, thus reducing this difference. It will also be seen that for the taste groups the visual cue preceded the relevant taste stimulus, whereas for the visual groups the taste cue followed the visual: at least, however, the CS-UCS interval was the same for the two conditions. Conditioning was carried out according to a standard classical discrimination procedure: two stimuli were presented in random sequence, one stimulus (the CS+) being followed by an aversive UCS, the other stimulus (CS-) not being followed by the UCS. For Groups 1, 2, 3 and 4, the UCS was electric shock; for Groups 5, 6, 7 and 8, the UCS was the unpleasant odor. Groups 1, 2, 5 and 6 were the four experimental groups, receiving the UCS contingent on presentation of the CS+. Groups 3, 4, 7
170
CAROLJ. BUSCHand
IAN
M. EVANS
Table 1. Factorial design UCS Contingency
CS
Ss
Discrimination CS* CS,
Color
12 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
12 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Color
8 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
8 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Color
12 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
12 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Color
8 1. Red salt 2. Red CA 3. Orange salt 4. Orange CA
Orange salt Orange CA Red salt Red CA
Taste
8 1. Red salt 2. Orange salt 3. Red CA 4. Orange CA
Red CA Orange CA Red salt Orange salt
Group
Contingent
Shock
Random
Contingent
Smell
Random
and 8 were presented with the same number of UCS as the experimental groups but received these on a random basis. The design is summarized in Table 1. The stimuli used in conditioning were presented as a visual-gustatory compound for all Ss, but for Groups 1, 3, 5 and 7, the only discriminable difference between the CS+ and the CS- was a visual cue (red vs orange), whereas for Groups 2, 4, 6 and 8, the only discriminable difference was the taste of the stimuli (citric acid vs salt). All groups were balanced with respect to which color or which taste was the CS + and which the CS - . Each S received a total of 28 stimulus presentations (trials): two presentations of the CS+ unpaired with the UCS were followed by 13 trials each of the CS + and CS - . The conditioning was terminated before reaching the last two cups on the tray in order to reduce any effects due to relief. Ss participated in the experiment knowing only that the intent of the study was to improve current methods of treating alcoholics, that it involved electric shock or an unpleasant odor, and that no alcoholic beverage would be used. The S was seated in the experimental room in front of two holders, one containing the four flavored liquids and the other containing the four colored liquids. The S was then instructed to taste the flavored liquids and rate each one on the semantic differential forms in front of him. The tastes were identified by number only. The S was then instructed to rank order these four cups, placing them according to his preference in any four
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171
of the 12 numbered wells in the holder. The same procedure was followed for the colored liquids with the exception that the S looked at these rather than tasted them. Upon completion of the above, E removed the holders and semantic differential forms and prepared the Ss for conditioning. All Ss, regardless of which UCS they were to receive, had the electrodes strapped to their arms. All Ss also had the band placed around their heads and the tube inserted into their left nostril, which provided a gentle steady flow of air directly into the nose. This was to control for any unpleasant effects caused by the apparatus rather than the UCS per se. The E then returned to the control room and adjusted the shock level for those Ss assigned to the shock UCS groups. These Ss received a total of three shocks in increasing intensity and were asked after each one to rate it on a lo-point scale of severity (1 was very mild, 10 was very unpleasant). The typical shock level selected was 0.7 mA AC (R.M.S.) and the range was from 0.3 to 1.0 mA. The mean rating was 7.81 and the range was 4 to 10. Those Ss assigned to the smell UCS groups also received three puffs of the pyridine and were asked to rate each puff on the same lo-point scale. The E had no way of adjusting the intensity of the odor but this procedure was followed, nonetheless, with the smell groups in order to equate their experience with the UCS with that of the shock groups. The mean rating was 7.80 and the range was from 3 to 10. The conditioning procedure itself has already been described. After the conditioning trials, E returned to the experimental room, removed the apparatus and repeated the preference rankings. The S then completed a brief questionnaire regarding perceived purpose of the experiment, and was dismissed. Feedback regarding the true purpose of the experiment was given at a later date.
RESULTS The dependent measures in this study were slightly different from those of the earlier investigation. The free-drinking test used before seemed unsound and was dropped. Three of the four performance measures were no longer appropriate for the modified design: response latency, as the Ss had to reach more varied distances; cup-to-lip time, as the taste groups could not tell which substance they were raising to their lips until they had tasted it; duration, as spit-out time in this study was regulated. The semantic differential was broken down into two dimensions: evaluative, as before, and anxiety. The ranking of the CSs with other stimuli was retained in modified form. Altogether, then, there were five dependent variables, each of which will be discussed in turn. The data were explored by means of analyses of variance and covariance; where individual comparisons between means are reported, significance was determined by Duncan’s New Multiple Range Test. Sip size
These data were averaged over four trial blocks. The first block contained the two test trials (CS+ without the UCS). and the first two conditioning trials (which were both CS - trials), and was therefore common to both CS+ and CS - performance curves. The second block contained the 2nd, 3rd, 4th and 5th presentation of the CS+ (for the CSt curve) and the 3rd, 4th and 5th presentation of the CS- (for the CScurve). The third block contained the 6th, 7th, 8th and 9th presentation of the CS+ and of the CS-. The final block contained the lOth, llth, 12th and 13th presentation of the CS+ and of the CS-. An analysis of covariance was then performed with the scores on the first trial block being the covariate for the within-subject analysis. It was expected that the size of the CS+ sips would be smaller than the CS- sips, but only for the contingent UCS groups (with the random groups there in no CS+/CSdistinction). The contingency/CS interaction however, proved to be non-significant (F = 1.83, df = 1,72, p > 0.10). It might also be expected that there would have been a greater decrease in sip size across trials for the groups that had contingent UCSs,
CAROL J. BUSCH and IAN M.
172
EVANS
but that interaction also failed to reach significance (F = 0.15, df= 2,144, p > 0.10). Individual comparisons among group means showed that only Group 1 showed a significant (p < 0.05) difference between CS+ and CS- sip sizes over Blocks 2, 3, and 4 of the conditioning trials. Visual inspection of the data revealed one other striking effect. Whereas all the groups receiving shock as the UCS decreased their sip sizes over trials. three of the four smell UCS groups increased sip-size across trials. Based on the subjective experiences of the authors, it is believed that the pyridine stimulated taste receptors and that larger sips helped wash away that unpleasant sensation. If this speculation is correct. it helps explain the differences between the present and the previous findings on this measure and shows the difficulties in establishing an unobtrusive behavioral measure that will be consistently appropriate. Semantic diflerential: evaluative scale
Figure 1 shows the group mean scores on the evaluative scale for the CS+ and CS- before and after conditioning. Since each S’s score was obtained by totalling his rating of three adjectival pairs correlating with the evaluative dimension, the maximum “pleasant” rating that could be obtained was 3, and the maximum “unpleasant” rating was 21. In the analysis of variance the main pre/post effect was significant (F = 14.10. df = 1,72, p < O.OOl), as was the interaction of pre/post by CS (F = 9.05, df= 1,72, p < 0.01) and the interaction between pre/post, CS, and contingency (F = 4.01, df= 1,72, p < 0.05). An examination of the means for the individual groups revealed that Group l’s postconditioning rating of the CS+ was significantly more negative than the pre-conditionUCS
I
Shock
Contingent
Random Taste
Color
Color UCS
Smell
L
Contfngent
COlOr
Taste
Taste
Color
Random
’
L
Taste
Fig. 1. Mean scores on the Evaluative scale of the Semantic Differential before and after conditioning trials. The higher the column, the more unpleasant the CS was rated. (Maximum negative rating = 21).
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173
and foul odor
UCS Shock l5-
2 a f
lo-
5.
cst
c5+ cs-
cs-
cs,
cs2
Contmgent Color
CS,
cs2
Random Toste
Color
UCS
Taste
Smell E+ avlor E
5-
Contingent Color
Rondom Toste
Color
Taste
Fig. 2. Mean scores on the Anxiety scale of the Semantic Differential before and after conditioning trials. The lower the column, the more anxious the CS was rated. (Maximum anxiety rating = 3; minimum anxiety rating = 21).
ing rating (p < 0.05). The only other group to show a significant pre-post change in rating was Group 3 (Shock/Random/Color-again this was in the expected direction as these control Ss rated both CS, and CS2 more negatively after conditioning (p < 0.05). It can also be seen from Fig. 1 that the Ss consistently rated colored stimuli more (F = 38.33, positively than taste stimuli both before and after conditioning df = 1,72, p
diferential:
anxiety
scale
Figure 2 shows the group mean scores on the anxiety scale for the CS+ and CSbefore and after conditioning. The maximum anxiety score that could be obtained was 3 and the maximum “calmness” score possible was 21. Although the overall pre/post effect was not significant (F = 2.78, df= 1,72, p > O.lO), the UCS by contingency by CS by discrimination by pre/post was significant (F = 5.31, df = 1,72, p < 0.05). Comparisons of group means indicated that only one group showed a significant difference in pre/post ratings for CS+ and that was Group l-after conditioning the CS+ was rated as more anxious. None of the other pre/post changes, in any direction, were significant. The changes on the anxiety scale were thus smaller and fewer than on the evaluative scale which may indicate that the UCSs affective properties were more in the nature of discomfort than of fear. Rank order
In the previous report, rank order differences were calculated; however in this study, there were 12 possible positions and only 4 substances to be ranked, so absolute rank
CAROL J. BUSCH and IAN M. EVANS
174
UCS
cs+
cs-
Color
Shack
cst csContingent Taste
UCS
cs,
cs2
Color
Fig. 3. Mean ranking
cs2
Taste
Smell
_
Conhngent
Color
cs, Random
c
Random Taste
Color
before and after conditioning. The higher the column, the ranking. (Maximum negative ranking = 12).
Taste
the more
negative
positions were the data analyzed. The mean rankings for each group before and after conditioning are depicted in Fig. 3. Analysis of variance of these means showed that there was a significant main effect due to nature of the CS in which the taste stimuli were ranked more negatively than the color stimuli (F = 16.57, df= 1,72, p < 0.001). There was also a significant pre/post main effect (F = 11.17, df = 1,72, p < 0.01) and a significant interaction between pre/post and the nature of the CS: rankings tended to become more negative when the stimulus ranked was a color, and to remain unchanged when the stimulus ranked was a taste (F = 17.93, df= 1,72, p < 0.001). The easiest way to obtain a picture of theses results is by the pattern of individual mean differences that reached significance: significant individual pre/post differences were found only with Group 1 (in which the CS+ was ranked more negatively after conditioning), and with Group 3 (in which both CSs were ranked more negatively after conditioning). These findings directly parallel the findings with the evaluate dimension of the semantic differential. DISCUSSION
The most striking finding of this study was that saturated pyridine vapor blasted up the nostrils of the Ss did not prove to be an effective UCS whether the CS was a visual or gustatory cue. There are a variety of possible reasons for this failure whose validity only future research can determine. One possibility is that the pyridine was not sufficiently aversive. This seems unlikely as the Ss gave equivalent ratings to it and the shock in test trials, and habituation to its noxious properties appeared less than is the usual case with shock-Ss reported the smell UC’S as being increasingly unpleasant. The pyridine blast might have been avoidable to some extent; if the Ss
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175
had held their breaths or breathed out hard through their noses, they might have been able to reduce significantly the discomfort, although the way the apparatus was arranged they would have received the stimulus eventually. Time relationships between the CS and UCS were also conceivably influenced by the aftertaste of the pyridine. In any event, while disrupted time relationships might have reduced the CS +/CS - discrimination, overall pre/post differences should still have been in evidence. No such changes were seen in the present study and pyridine does not, therefore, seem to be a promising stimulus for applied aversive conditioning. More prolonged trials or longer UCS durations could be harmful to the subject as pyridine is toxic. A second feature of the study was the failure to find conditioning to taste CSs with either shock or foul smell as the UCS. Thus a finding of the previous study was not replicated with what we consider to be an improved design. We would caution, however, against any “biological preparedness” interpretation until much more obvious factors have been excluded. In our attempt to make the taste CSs less aversive to begin with, weak concentrations were used, which may have been difficult for some Ss to discriminate. Further, although we also made the color CSs less attractive (using orange and red solutions which tend to be disliked by Ss) we were still dogged by significant starting differences between color and taste stimuli as in the previous study on the evaluative scale. Fortunately this was not true of the semantic differential anxiety ratings. A third point to notice is that while we tried to keep CS-UCS intervals constant in this study, there is an inevitable difference in CS-UCS relationships when the CS is a compound with either color or taste the crucial element. If the results were to be summarized one could say that with color CSs and shock UCSs, a small but statistically significant conditioning effect was found which was revealed by indirect behavioral and attitudinal measures. It is interesting that one of the control groups (Group 3) appeared to show a “conditioning” effect; we do not feel that this invalidates the conditioning procedure as this group showed change in both CSs-this can be accounted for by occasional chance pairings with the random shock or by the continued presence of cups of liquids as static apparatus cues (see Evans, 1976, for discussion pertinent to these two assumptions). None of the control groups fully eliminated the problem of experimental demand effects, although it is not clear why this variable did not operate on the unpleasant odor groups and taste/shock group. In general it must be admitted that this type of study does not provide an ideal link between pure laboratory conditioning studies and clinical aversion therapy, as it is analogous to neither-it lacks the direct CR measurement and masking procedures of the human conditioning experiment, and lacks the stimulus aversiveness justifiable in a clinical investigation. As mentioned elsewhere (Evans, 1976) it may be necessary to pursue this line of research in well-controlled treatment studies. REFERENCES BITTERMAN M. E. (1975) Issues in the comparative psychology of learning. In The Evolution of Brain und Behaaior in Vertebrates (Eds. R. B. MASTERTON. M. E. BITTERMAN, C. B. G. CAMPBELL and N. HOLTEN). Erlbaum. New York. ELKINS R. L. (1974) Conditioned flavor aversions to familiar tap water in rats: An adjustment with implications for aversion therapy treatment of alcoholism and obesity. J. ahnorm. Pspchol. 83. 41 l-417. EVANS I. M. (1976) Classical conditioning. In The Experimental and Theoretical Bases 01 Behmiour Therapy (Eds. M. P. FELDMAN and A. A. BROADHURST). Wiley, London. EVANS I. M. and BUSCH C. 1. (1974) The effectiveness of visual and gustatory conditioned stimuli in human classical aversive conditioning with electric shock. Brhar. Res and Therapy 12, 129-140. GARB J. L. and STUNKARD A. J. (1974) Taste aversions in man. Am. J. Psych& 131, 1204-1207. HALLAM R., RACHMAN S. and FALKOWSKI W. (1972) Subjective, attitudinal and physiological effects of electrical aversion therapy. Behm Res. and Therapy 10, l-13. O’DONNELL C. R. (1973) The measurement of anxiety and evaluative components in exam and speech concepts for males. J. c/in. Psxchol. 29, 326-327. OSWJOU C. E.. SKI G. J. and TANKENBAUM P. H. (1957) The Measurwe~~t of’ Mrunim~. University of Illinois Press, Urbana. REVUSKY S. (1973) Some laboratory paradigms for chemical aversion treatment of alcoholism. J. Behac. Ther. exp. Ps.whiat. 4, 15-17. WILSON G. T. and DAVIXIN G. C. (1969) Aversion techniques in behavior therapy: Some theoretical and metatheoretical considerations. J. consult. clin. Psychok 33, 327-329.