Goal Activation, Expectations, and Placebo Analgesia

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DESCRIPTION (provided by applicant): A great deal of research indicates that placebos can have strong analgesic effects. Despite the large number of studies incorporating placebo as experimental controls, until recently, there have been relatively few empirical investigations into the mechanisms responsible for placebo analgesia. The research that has examined the mechanisms underlying placebo analgesia has focused almost solely on classical conditioning and expectations as the casual mechanisms. A third factor that may contribute to placebo analgesia, motivation, has received virtually no attention. Based on the social-cognitive literature on automatic processing and nonconscious goal activation, we have developed a model of placebo responding which incorporates motivation as a causal variable and should enable us to discern more readily when and how placebos will have analgesic effects. The model proposes that placebo effects are most likely to occur when individuals hold a goal that can be fulfilled by confirming a placebo expectation. Three experiments are proposed to demonstrate that goals and placebo expectancies interact in causing placebo analgesia. In each experiment both placebo expectations and goals will be manipulated. A unique feature of the proposal is that we will examine nonconscious goals. Nonconscious goals are particularly useful in determining the contribution of goals to placebo analgesia as these goals are unlikely to be confounded with factors such as changes in expectancies and moods. To further test of our hypothesis that goals alter placebo analgesia, we will also test whether the findings display two primary qualities of goal. Finally, we will also measure physiological reactions to the pain stimulus as a potential mediator of the proposed effects. There is substantial evidence that treatments for acute and chronic pain often benefit from powerful placebo analgesic effects. There is no consensus, however, on how and when placebo analgesia occurs. In three experiments, a theory-driven approach will be taken to determine how and when one's current motives alter placebo analgesia. A better understanding the role of motivation in placebo responding has important implications for future clinical trials as well as ongoing efforts to alleviate chronic and acute pain.