Cognitive dissonance and the placebo response: The effect of differential justification for undergoing dummy injections

Studied the effects of cognitive dissonance on pain perception and attitudes towards injections in 48 student subjects of both sexes (average age = 20.5). In a ‘forced compliance’ design, subjects received sets of painful radiant heat stimuli, projected to their inside forearms, which they rated for painfulness and to which their GSR amplitude was recorded. During these stimuli, they ‘chose’ to receive an experimental (placebo) injection. The degree of justification for agreeing to be injected was varied. Subjects in the high-justification (HJ) condition were paid for their compliance, while subjects in the low-justification (LJ) condition were not paid. Two predictions were made from dissonance theory. The first prediction, that only LJ subjects would manifest significant post-injection analgesia when compared to subjects in a no-choice control condition, was confirmed, considering both pain ratings (p < 0.01) and GSR (p < 0.025). The second prediction, that only LJ subjects would rate injections more favourably than control subjects on a post-experimental measure, was not confirmed. The relevance of these findings to explanation of the placebo effect is discussed.