Effects of masking during interstimulus and intertrial intervals on differential conditioning of electrodermal responses



Journal Title

Journal ISSN

Volume Title



When classical conditioning of electrodermal responses (EDRs) has been investigated, it has consistently been associated with the S's ability to correctly verbalize the CS-UCS relationship. In light of these findings, it would be predicted that a conditioning paradigm which is embedded in a masking task designed to interfere with recognition of the stimulus contingencies would not result in differential conditioning of the EDR. However, this prediction is strikingly contradicted in an earlier study (Fuhrer and Baer, 1969) involving performance of a masking task during the interstimulus Interval. Evidence for reliable EDR conditioning was obtained for Ss unable to verbalize the stimulus relations during a postconditioning interview. The present investigation employed a probability learning task with the purpose of masking the CS-UCS relationship in order to further analyze interstimulus interval masking and to compare its effects to intertrial interval masking. In addition to a conventional (non-masked) control group (N=15)» three experimental groups (N=29 each) were studied: one masked during the interstimulus interval, one masked during the intertrial interval, and one masked during both of these intervals. The Ss, all college-aged males, received 6 adaptation and 37 acquisition trials in a differential EDR conditioning paradigm. Lights of two different hues, 8 sec. in duration, were employed as the CSs. The UCS was a 250- msec., tolerance-level shock presented coincidentally with the offset of the CS+. Intertrial Intervals were 30 - sec. For the purpose of analysis, EDRs were classified as being in one of three temporal intervals depending upon the latency of the response. First interval EDRs were those which began in a sec. period originating 1 sec. after CS onset, second Interval responses were those beginning In a 4-sec. period terminating 1 sec. after CS offset. Third interval responses were those which occurred in a 4—sec. period beginning 1 sec. after CS offset. A post-conditioning interview was used to classify Ss as accurate verbalizers, i.e., those verbalizing recognition of the CS-UCS relationship, or inaccurate verbalizers, i.e., those falling to recognize the CS-UCS relationship. Three Judges with no knowledge of Ss EDR performance rated each S on the basis of the Interview. The results indicated that 89% of the control Ss and approximately 60%, of the masked Ss in each experimental group were classified as accurate verbalizers. Thus, while masking reduced the number of Ss able to recognize the CS-UCS contingencies, the various masking procedures did not differ in this regard. For first interval EDRs, all groups exhibited significant differential conditioning, and the groups did not differ In the extent of conditioning. Second interval EDR conditioning was limited to the non-masked control group. For third interval responses, both the control group and the group masked during the intertrial interval exhibited conditioning. The conditioning manifested by the accurately verbalizing Ss, was almost identical with that of the total group. The one notable exception occurred for second Interval EDRs recorded during the latter half of the acquisition trials. During these trials accurately verbalizing Ss did show a tendency to condition though this performance was not discernible within the total group. The present study confirms the earlier results of Fuhrer and Baer (1969) in indicating that a reliable degree of differential conditioning of first interval EDRs is observable for inaccurately verbalizing Ss who have undergone Interstimulus interval masking. Similar conditioning was also noted for third interval EDRs in the present study. Comparable results were not obtained for inaccurate subgroups which underwent either intertrial masking or both interstimulus and intertrial masking.



Galvanic skin response, Conditioned response