The elicitation and habituation of orienting and defensive responses to phobic imagery and the incremental stimulus intensity effect.

Abstract

ABSTRACTUsing imaginal stimuli, the present investigation examined psychophysiological responses to imagery and the roles of Groves and Thompson's (1970) dual process theory and Sokolov's (1963) model of the defensive response(DR) in mediating the incremental stimulus intensity effect (ISIE). Experiment I was undertaken to determine whether phobic and neutral imagery could be discriminated by DRs and orienting responses (ORs). In a within groups design. 19 analogue speech phobics were exposed to 4 neutral and 4 phobic scenes. Dependent measures were skin conductance measures and second‐by‐second heart rate (HR). The results showed that DRs occurred only in response to phobic scenes. In a between groups design. Experiment II compared an incremental series (IS) of 16 phobic imaginal stimulus presentations to a constant series. Subjects were analogue speech phobics with 14 subjects per condition. For both conditions the last 4 scene presentations were the same. Dependent measures were second‐by‐second HR, second‐by‐second cephalic pulse amplitude, and skin conductance measures. The results showed greater habituation in the IS condition, but were inconclusive with regard to the roles played by dual process theory and the DR model in the ISIE.