Source
Department of Psychology, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606-3390, USA. ageers@utnet.utoledo.edu
Abstract
OBJECTIVE:
Prior investigations have failed to find reliable personality differences in placebo responding. The present study tests the hypothesis that personality and situational variables interact to determine placebo responding.
METHODS:
Optimists and pessimists were randomly assigned to one of three conditions. In the first condition, the participants were told that they were to ingest a pill that would make them feel unpleasant (deceptive-expectation group). In the second condition, the participants were told that they were to ingest a pill that would make them feel either unpleasant or was an inactive substance (conditional-expectation group). Finally, a third group was told they were to ingest a pill that was inactive (control group).
RESULTS:
Pessimists were more likely than optimists to follow a negative-placebo expectation when given a deceptive expectation, but not when given a conditional expectation.
CONCLUSION:
The personality variable optimism-pessimism relates to placebo responding when individuals are given a deceptive but not a conditional expectation. This suggests that personality and situational variables interact to determine placebo responding.