Implausibility inhibits but does not eliminate false autobiographical beliefs.

The role of the plausibility of suggested events in the formation of false autobiographical beliefs and memories has long been debated. In two studies, the shape of the relationship between presuggestion personal plausibility and the development of postsuggestion false beliefs was examined. Participants rated personal plausibility and autobiographical belief for childhood events. They later received a suggestion that an unlikely event occurred during their childhood and provided postsuggestion ratings. The best fit was a curvilinear relationship between plausibility and belief, with the lowest risk for false belief at the plausibility scale floor. Above this threshold, the risk for false belief increased sharply and remained similar across all other levels of plausibility. A minority of those who initially viewed the event as highly implausible showed increased beliefs; this was accompanied by large increases in personal plausibility. We conclude that only extreme implausibility inhibits suggestion-induced false autobiographical beliefs, unless suggestions cause increases in plausibility ratings.