Social brain volume is associated with in-degree social network size among older adults

Seyul Kwak, Won Tak Joo, Yoosik Youm, Jeanyung Chey

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)


The social brain hypothesis proposes that large neocortex size evolved to support cognitively demanding social interactions. Accordingly, previous studies have observed that larger orbitofrontal and amygdala structures predict the size of an individual’s social network. However, it remains uncertain how an individual’s social connectedness reported by other people is associated with the social brain volume. In this study, we found that a greater in-degree network size, a measure of social ties identified by a subject’s social connections rather than by the subject, significantly correlated with a larger regional volume of the orbitofrontal cortex, dorsomedial prefrontal cortex and lingual gyrus. By contrast, out-degree size, which is based on an individual’s self-perceived connectedness, showed no associations. Meta-analytic reverse inference further revealed that regional volume pattern of in-degree size was specifically involved in social inference ability. These findings were possible because our dataset contained the social networks of an entire village, i.e. a global network. The results suggest that the in-degree aspect of social network size not only confirms the previously reported brain correlates of the social network but also shows an association in brain regions involved in the ability to infer other people’s minds. This study provides insight into understanding how the social brain is uniquely associated with sociocentric measures derived from a global network.

Original languageEnglish
Article number20172708
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1871
Publication statusPublished - 2018 Jan 31

Bibliographical note

Publisher Copyright:
© 2018 The Authors.

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)


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