Shared group membership facilitates the persistence of culturally transmitted behaviour

Cultural transmission allows humans, and several other species, to create distinct cultural traditions and cultural repertoires. While the spread of innovations is well researched, much less focus has been given to factors allowing for novel behaviour to persist within a group so that novelties become cultural traditions. Here we show experimentally that group membership is a key factor in determining the stability of horizontally transmitted behaviour, and corroborate our findings with immigrant survey data. In two experiments, the perception of a shared group membership led to persistence of transmitted behaviour (tapping speed) across several days, indicating long-term stability. In contrast, where no shared group membership was perceived, transmitted behaviour was shown during immediate interaction with others but was quickly lost over time, indicating short-lived compliance. Consistent with our findings, a re-analysis of survey data from British Bangladeshi migrants indicates that identification with the host group facilitates horizontal transmission. Our data suggest that group membership is of considerable importance for our understanding of cultural diversity, immigrant acculturation, and the maintenance of behavioural change. Our study highlights the hitherto underappreciated relevance of social factors in our understanding of cultural transmission and evolution.