Control of aversive stimulus termination in systematic desensitization

Indirect experimental evidence does not support Wolpe's (1958) notion that desensitization to an item early on the hierarchy is a prerequisite for movement to a more aversive item lest residuals of anxiety may summate and lead to sensitization. An experiment involving forty female snake-phobics was conducted to test this contention directly. In addition to two control groups of no treatment (NT) and pseudodesensitization (PD), two other groups were used. All Ss were matched on their pre-treatment fear of a live snake and randomly assigned to the groups. One group was treated by Wolpean procedure (SD) wherein two successive presentations without signalling were set as criterion for movement to the next item. The other (YSD) was yoked to the SD group but neither had control over termination of the aversive stimulus nor was necessarily desensitized to early items before the more aversive ones were attempted. The SD and YSD improved equally and significantly better than the PD and NT (p<0.01) while neither control group changed. The same changes were maintained in a follow-up. These results paved the way for devising standardized treatments, scheduled and taped in advance, applicable to individuals and groups alike.