Robin Dunbar

Who they are

Dunbar is an evolutionary psychologist whose career-long subject is the relationship between group size, social bonding and cognition, first in primates and then in humans. His academic home is the Department of Experimental Psychology at the University of Oxford, where he holds emeritus status, and he is a Fellow of Magdalen College.

His name is attached to a single number, 150, which is the part of his work that escaped academic journals and became general knowledge, quoted in management books and social-media commentary as the size limit of a group a person can meaningfully know. That figure is one layer of a larger model. Working with Matt Spoors, Dunbar found that social networks arrange into consistent nested rings: a support clique of around five, a sympathy group of about fifteen, then wider bands of roughly fifty and a hundred and fifty. The rings were defined functionally rather than sentimentally. Rather than asking survey respondents who they liked, Dunbar and Spoors asked who they would turn to in severe emotional, social or financial distress, a blunter question that stripped out pleasant acquaintances who would not actually show up.

The layered shape of the model has held up more consistently in later research than the specific ceiling of 150, which has been challenged on statistical and methodological grounds by researchers working with different samples and methods. Dunbar has continued to write for a general audience across three decades, moving from the origins of language and gossip to friendship, love and human evolution more broadly. His five most substantial trade and crossover books are listed below; he has written around fifteen books in total.

Books

Dunbar has written around fifteen books in total; these five are the ones most relevant to this site.

Key papers

Dunbar, R. I. M., & Spoors, M. (1995). Social networks, support cliques, and kinship. Human Nature, 6(3), 273-290.

Dunbar, R. I. M. (1992). Neocortex size as a constraint on group size in primates. Journal of Human Evolution, 22, 469-493.

Key ideas

The support clique, defined by crisis rather than affection. Dunbar's number is popularly remembered as a single ceiling, but the more original part of the 1995 paper with Spoors is the innermost layer: a support clique of around five people, defined by who a person would turn to if their life fell apart, not by who they like best.

Nested rings, not one number. The model layers outward from the support clique through a sympathy group of about fifteen to bands of fifty and a hundred and fifty, with emotional intensity falling steadily as the rings widen. The layered structure has replicated more consistently across later studies than the specific value of the outer ring.

Two disciplines converging on one number. Marilynn Brewer's optimal distinctiveness theory arrives at similarly sized in-groups from social psychology rather than evolutionary anthropology. Read side by side, the two lines of research reach comparable group sizes by different routes, a stronger form of evidence than either taken alone.

The layered model underneath belonging. Dunbar's work supplies the structural account of what a person's social world is actually made of, which this site treats as the scaffolding beneath the broader idea of belonging.

Concepts on this site

Dunbar's number, the layered model of social ties he developed with Matt Spoors

Belonging, the underlying need his layered structure is organised around

Optimal distinctiveness theory, Marilynn Brewer's convergent account from social psychology

Find them elsewhere

Scholar profile carries a verified psy.ox.ac.uk email, matching his Oxford department. No personal social accounts found

Checked 2026-09-10. Handles and affiliations go out of date, so treat this block as a snapshot rather than a standing fact.

---