Biases in cultural transmission of information about a minimal ingroup

Group membership and our beliefs about the groups we belong to are the building blocks of our social and cultural identity. Here, we investigated whether transmission of information about how often different personality traits occur in a minimal ingroup and outgroup results in distinct patterns of cultural evolution. Participants transmitted information about the occurrence of positive, negative and neutral traits to other participants in linear transmission chains. First, we found a general tendency for occurrence of all traits to decrease across generations. However, our control experiment revealed that this general decrease was not specific to transmission of information about traits but represented a low-level response bias. Critically, this decrease across generations was smaller when participants were transmitting information about ingroup than outgroup traits, but only for positive and neutral traits. No significant difference emerged for negative traits. Together, these results show that minimal group membership can selectively bias transmission of information about ingroup and outgroup. We propose that this results from two processes: an ingroup-positivity bias and higher accuracy when transmitting ingroup-related information. Overall, our study provides an example of how examining mechanisms of cultural transmission can elucidate our understanding of processes of formation and evolution of social-cultural identity.