The evolution of personal standards into social norms

Social norms have become a conceptual cornerstone in the study of human decision making across the social sciences. The functions of social norms in guiding individual and collective decision-making have been extensively scrutinized empirically, too. However, possible evolutionary origins of the psychological mechanisms required to carry out these functions are less well understood. In particular, trajectories from individually adaptive to socially functional heuristics for norm formation have rarely been studied. Here, we trace such a trajectory. We present a model that allows for the comparison of two heuristics broadly applicable across individual and social decision contexts: ‘rejoicing’ own achievements vs. ‘regretting’ missed opportunities. We find that (i) both perform better than the homo oeconomicus benchmark in individual decision problems under plausible ecological assumptions and (ii) each is adaptive in different environments. We argue that observation (i) provides a potent microfoundation for social norms as a product of co-optation of individually evolved heuristics, i.e., a reduction of social norm formation to the evolution of individual traits. Moreover, observation (ii) lends itself to empirical testing, thus laying the ground for a new wave of studies in the literature fascinated with human norm psychology.