The meaning of social complexity: insights from a theoretical treatment of the social brain hypothesis

This work builds on a rich discourse surrounding the social brain hypothesis as well as the definition and quantification of social complexity. We believe this manuscript provides a new perspective on the topic by pairing a conceptual framework with an evolutionary model. This treatment of the topic allows us to analyse the social brain hypothesis with a focus on social complexity rather than controversies related to ecological covariates and brain measurements. We show that even in the confines of a simplified and idealized model, quantifying social complexity a priori can be intractable. As a result, we believe that we should generally approach metrics of social complexity with skepticism. This has general implications for empirical tests of the social brain hypothesis and practical implications for those trying to design a metric of social complexity. We provide recommendations for future researchers studying the social brain hypothesis and offer a starting point for mathematical treatments of social complexity.