A debate on Robin Dunbar’s social brain hypothesis


This post is part of a Webinar, Debating Dunbar's Number.

Part 1 — Part 2Part 3


Some months ago, an article by Jan de Ruiter, Gavin Weston and Stephen Lyon appeared in American Anthropologist. The paper's target is Robin Dunbar's Social brain hypothesis. The hypothesis comes in many varieties; one might sum it up as the view that our cognitive capacities keep the amount of friends we can have under a fixed threshold, and constrain the size of primate societies. (This summary is inadequate in many ways, as I hope this debate will show.)

Dunbar's hypothesis is one of the most popular piece of cognitive anthropology out there. It is also one of the most criticized in anthropological circles. Our site wouldn't be true to its vocation if it did not invite all the protagonists to an open debate.

This week, Jan de Ruiter and his coauthors, as well as Robin Dunbar, will react on two posts, one defending the social brain hypothesis (posted today), the other defending the critics (to appear wednesday). Everyone from the ICCI community is welcomed to chime in.

Link to Jan de Ruiter et al.'s article.

Link to Robin Dunbar, 'The social brain hypothesis' (1998).





  • comment-avatar
    Jayarava Attwood 4 June 2012 (13:51)

    I thought Dunbar’s hypothesis was a lot softer than this. Something like:

    “Social animals are observed to form structured groups, where the size of group and it’s sub-units tend towards certain numbers, the average which is species dependent. This average group size is correlated to average neocortex size across a range of social species, which suggests that neocortex size be a limiting factor for group size.”

    One of the fascinating things about Dunbar’s research is how rapidly people came to see it as deterministic and prescriptive; whereas reading Dunbar’s original paper my sense was that his theory was descriptive, though with predictive power. It’s as though there is another neocortex limit on the amount of time a theory exists before we treat it as an absolute; on on the amount of uncertainty we can tolerate at anyone one time.

    I’d also note that Dunbar tells us nothing about non-social species, or about those social species with no neo-cortex (such as insects).

  • comment-avatar
    Olivier Morin 4 June 2012 (15:10)

    Dear Jayarava — as this post said clearly, the hypothesis bears on primate societies alone.. This quick introduction does not suggest it could apply to other species, much less to non-social species.