The Goldilocks Placebo Effect: Placebo Effects Are Stronger When People Select a Treatment from an Optimal Number of Choices

摘要

People are often more satisfied with a choice (e.g., chocolates, pens) when the number of options in the choice set is "just right" (e.g., 10-12), neither too few (e.g., 2-4) nor too many (e.g., 30-40). We investigated this "Goldilocks effect" in the context of a placebo treatment. Participants reporting nonspecific complaints (e.g., headaches) chose one of Bach's 38 Flower Essences from a choice set of 2 (low choice), 12 (optimal choice), or 38 (full choice) options to use for a 2-week period. Replicating earlier findings in the novel context of a health-related choice, participants were initially more satisfied with the essence they selected when presented with 12 versus either 2 or 38 options. More importantly, self-reported symptoms were significantly lower 2 weeks later in the optimal (12) versus nonoptimal choice conditions (2 and 38). Because there is no known active ingredient in Bach's Flower Essences, we refer to this as the Goldilocks placebo effect. Supporting a counterfactual thinking account of the Goldilocks effect, and despite significantly fewer symptoms after 2 weeks, those in the optimal choice set condition were no longer significantly more satisfied with their choice at the end of testing. Implications for medical practice, especially patient choice, are discussed.