Scholars in many fields have long noted the importance of social context in the development of political ideology. Recent work suggests that political ideology also has a heritable component, but no specific gene variant associated with political ideology has so far been identified. In this...

Human behaviour is thought to spread through face-to-face social networks, but it is difficult to identify social influence effects in observational studies 9–13, and it is unknown whether online social networks operate in the same way 14–19. Here we report results from a randomized...