Intergroup bias in perceived trustworthiness among few or many minimal groups

In diversifying societies, people are inevitably exposed to an increasing number of outgroups. As impressions of outgroups are more negative than those of ingroups, this may overall lead to more negative social attitudes and behaviors. In six preregistered experiments (N_total = 1832) using a minimal group paradigm, we investigated whether the mere number of groups influences the perceived trustworthiness of ingroups, outgroups, and the total population. Our results consistently show that higher diversity does not decrease overall population trustworthiness, despite a larger number of outgroups. This is because of a stronger intergroup bias such that ingroups receive an additional boost in trustworthiness judgments when there are more outgroups. Our experiments show that these effects are not due to objective or perceived group sizes or greater attitude differences toward the group-defining attributes. Instead, people seem to perceive members of their ingroup as more similar to themselves if there is a higher number of outgroups and high similarity is related to high perceived trustworthiness.