Is Mentalizing Essential to Predict Human Network Size? Reexamining the Social Brain Hypothesis From a Social Network Perspective

Keywords: The social brain hypothesis, social network size, mentalizing, community


One central question in social science and evolutionary anthropology is how humans can form and maintain large social networks. The social brain hypothesis argues that humans use their mentalizing ability to read others’ minds for the development of dyadic relationships in layered social networks. However, previous empirical studies have not directly examined the association between mentalizing and the size of the active network located at the outermost layer. By introducing a social network perspective, we predicted that individuals use their mentalizing ability not only to form and maintain dyadic relationships but also to belong to multiple communities, which indirectly expands the active network size. We collected data from undergraduates in Japan (N = 175) to examine how mentalizing is linked to the size of online social networks. Mentalizing was positively associated with the number of dyads but not with the number of communities and the active network size. These findings suggest that the social brain hypothesis has limited validity, and there is a need for more careful explanations surrounding the psychological and structural underpinnings of large human social networks.

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