Cognitive capacity shapes both the "whether" and "how" of social learning

Social learning is widely understood as offering a mechanism to mitigate the costs and risks of individual trial-and- error exploration. This cost-avoidance account implies a framing of social learning as a resource-rational adaptation, which should be most beneficial to populations with limited capacity to learn asocially. But in cases of peer-to-peer transmission, that same limited capacity may hinder the reliability of social information--rendering it less, not more, useful. So how do these conflicting intuitions resolve? Across a series of simulation experiments, we find evidence for an inverse-U relationship where social information use emerges most strongly in populations with moderate capacity relative to the complexity of their environment. Furthermore, we demonstrate a coevolutionary transition in social learning strategies: as population capacity rises, selection pressure shifts from favouring a success bias to a conformist approach. Our findings highlight cognitive capacity as a fundamental constraint on the emergence of culture, determining not just if a species learns socially, but also how. An anonymised mirror of the source code for this project is available at https://anonymous.4open.science/r/capacity-and-social-learning-806F