Strangers in the dark: assumed similarity in judgments of unknown others on aversive personality

The need to maintain cooperation in social dilemmas is a fundamental challenge. Responses to social dilemmas are affected by dispositions toward exploitativeness (i.e., the maximization of one’s own utility) and distrust (i.e., the fear of being exploited by others). This is because the belief that others are untrustworthy justifies exploitative behaviors. The Dark Factor of Personality (D) is postulated to comprise the conjunction of these dispositions, implying that individuals will assume similarity on D. In this research, we sought to test this implication by examining whether individuals’ self- and observer reports of unacquainted targets on D converge. Across five studies, we found that individuals assume similarity on D when unknown targets are described as ‘typical’ (Study 1) or when shown a photograph (Studies 2–5). These effects were not moderated by the congruency between rater and target sex (Studies 2 and 3); however, we found that higher attractiveness of targets led to greater assumed similarity on D (Studies 4 and 5). These findings are consistent with D reflecting the conjunction of exploitativeness and distrust while also suggesting that assumed similarity on D is moderated by the interpersonal attraction of those being rated.