A demographic theory of similarity-biased social learning

We develop a demographic theory of similarity-biased social learning that formalizes our understanding of when and why individuals should preferentially copy others that look or act like them. We build an evolutionary model in which individuals can either learn on their own or copy others from a demonstrator pool that contains varying proportions of in-group and out-group members, and where group tags can be more or less informative about local knowledge. We find that where social learning becomes common, selection favors copying biases that track the direction of informational advantage---toward the group that tends to be better adapted to local conditions, including an anti-similarity bias when tags are negatively associated with local correctness (as may be the case for some immigrant communities). We also find conditions in which a similarity bias can stabilize social learning when such learners are already common, but not when they are rare, with implications for the role of group identities in cultural evolution. We discuss implications for understanding parochialism as risk aversion, majority-minority dynamics, the sociology of immigration, and the lasting impacts of colonialism.