The gene-culture coevolution of human decision-making

This thesis aimed to investigate both (i) the flexibility of social learning and (ii) the complexity of decision-making from a gene-culture coevolutionary perspective. I investigated three key areas of human decision-making: asocial skills, social norms, and cooperation by utilising a game against nature, a coordination game and a Prisoner’s Dilemma respectively. To address the first aim, chapter 3 investigated the social learning of asocial skills and social norms, and chapter 4 investigated the social learning of cooperation, in an empirical setting. The participants were more flexible than previously found. They adjusted their frequency-dependent social learning strategies to a third-order complexity, including: (i) the frequency of the choices made by the group from whom they learned; (ii) whether this group were identified as learning in a similar or different environment to the participant and (iii) the reliability of this similarity signal. There was an upper limit to this flexibility, as all participants found it easier to master asocial skills, social norms, and cooperative behaviours from groups of reliably similar others. To address the second research aim, chapters 5-6 used agent-based models to investigate whether the cognitive and motivational processes underlying decision-making were likely to be fully modular, partly modular, or domain-general. Fully modular psychology was necessary to acquire skills and norms in 2 distinct domains, though modular cognition was more important to skill acquisition. Domain-general agents were instead needed to uphold the costly levels of cooperation seen across human societies. Any agent may uphold suboptimal behaviour simply via drift. Together, these findings have implications for our understanding of how maladaptive behaviour is maintained via cultural evolutionary processes. Maladaptive behaviour may be upheld via both a trade-off in social learning flexibility and a trade-off in the complexity of decision-making, which in turn is impacted by drift.