Response expectancies: a psychological mechanism of suggested and placebo analgesia

Response expectancies, or the expectation of one's own non‐volitional reactions to situational cues, are hypothesized to be a psychological mechanism of both hypnotic and placebo responding (Kirsch, 1990). In this study, response expectancies were evaluated as a mediator of suggested and placebo analgesia using Baron and Kenny's (1986) classic method of testing mediation. One hundred and seventy‐two volunteers were randomly assigned to hypnotic analgesia suggestion, imaginative analgesia suggestion, placebo analgesia, or no‐treatment control conditions. The hypnotic, imaginative and placebo treatments were more effective than the no‐treatment control condition in relieving finger pressure pain. The hypnotic treatment was also more effective than the placebo. Each of the three treatments was partially mediated by response expectancies, although the percentage of mediation varied across the hypnotic (25%), imaginative (29%) and placebo (41%) conditions. The findings support the position that response expectancies are one of the major psychological mechanisms of suggested and placebo analgesia.