A uniqueness to personal threat (UPT) hypothesis: how similarity affects perceptions of susceptibility and severity in risk assessment.

In the literature, perceived risk is conceptualized as perceptions of both susceptibility and severity. Optimistic bias, the belief that one is less vulnerable than others to various diseases, is based primarily on assessments of personal susceptibility. In this article, the authors ask how perceptions of relative severity/susceptibility differ as a function of perceived similarity between oneself and a referent. Based on predictions from the optimistic bias literature, Study 1 (N = 67) manipulated similarity and measured both susceptibility and severity. As anticipated, ratings of susceptibility were negatively correlated with similarity. Ratings of severity, however, were unexpected in that they were highest for a similar referent. The uniqueness of personal threat hypothesis was proposed as an explanation for this finding, and this hypothesis was tested in Study 2 (N = 121). Results were mostly supportive. Findings indicated that individuals strategically use susceptibility and severity ratings to modulate their assessment of overall risk and personal identity.