Dunbar and Relatedness

Societies are complex open systems composed of the interaction of individuals that are themselves complex systems. Yet such systems can nonetheless achieve a level of dynamic stability giving rise to a social order which we label – civilisation. This is an emergent phenomenon that requires individuals to cooperate and reach consensus on key issues – an affinity to a group or groups.

The anthropologist Robin Dunbar is a leading figure in research linking brain size, specifically the neocortex, and the size of such groups. In the case of primates, such as apes and monkeys, grooming cliques of 40-60 were observed. By extrapolating to humans, maximum group sizes in the order of 150 are to be expected. This is the social brain hypothesis, i.e. we have developed larger brains because of the benefits offered by group affiliation – and similarly, the information processing capacity of our brain sets the ceiling on how large such groups can be.

Testing such hypotheses are difficult as it can be near impossible to construct an experiment in a human social system with clear boundaries and constraints. The research field known as agent based social simulation (ABSS) uses computer simulations to model such social processes and has been able to capture emergent phenomenon such as group size and affiliation consistent with Dunbar’s work. Such simulations have been able to successfully model previously intractable problems such as crowd behaviour around fire exists – resulting in practical real-world applications.

Dunbar notes that the various human groups identifiable in any society tend to cluster around sizes of 5, 12, 35, 150, 500 and 2,000. An observation which probably resonates with our individual experience. There is thus a convergence of evidence in anthropology, evolutionary and computer sciences for relatedness – the drive for humans to assess whether others are in or out of a particular group. From the field of neuroscience, we are beginning to surface explanatory mechanisms underlying such behaviour. Reward circuits are triggered when we observe others rated as similar to ourselves driving a toward empathetic response. We form a theory of mind which drives us to seek and affine to an in-group and distance ourselves from the out-group.

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