In his 1993 study Robin Dunbar took a look at the proportion of the cortical size (the outer part of the brain, that is involved in higher functions such as spatial reasoning, conscious thought, and language) to the total brain size, and compared the results with group sizes and language of humans beings. Dunbar developed an equation to calculate an average group size that a human being is able to overlook. The result was 147.8, with a rather wide range of possible variation from 100.2 to 231.1. These cognitive limitations of stable social relationships have come to be known as Dunbar’s number (Dunbar, 1993).
Other equations based on alternative indices of neocortical size have shown similar results such as the Jerison’s Extra Neocortical Neurons Index (107.6 – 189.1) or the absolute neocordical volume (248.6). Even other scholars (Mc Carty, Killworth, Bernard et al., 2000) that have also identified a coherent group number have come to results that were not necessarily inside Dunbar’s 100 to 231 range, but close (231 as a median, 290 as a maximum).
The average number of 147.8 is suggested to be a cognitive limit to the amount of people with whom an individual can maintain stable social relationships by personal contact. Social relationships are meant to be the case when “every member knows every other member, knows whether they are friendly or hostile, and knows the relationship among them.” (Christakis, Fowler, 2010).
Dunbar studied hunter-gatherer groupings, due to the idea that “our brain size has its origins in the later stages of human evolution some 250,000 years ago [...], we may assume that our current brain size reflects the kind of groups then prevalent and not those now found among technologically advanced cultures”. He found out that three social groupings could be identified: “overnight camps”, “band/village”, and “tribe”. The mean size of these groups were 38, 148, and 1,155 people, respectively. The size of a band/village fit right into the results of Dunbar’s calculations. Investigating further, Dunbar identified more examples of successful groupings that had a size of 100 to 230 people if not close to 150, such as fighting units in armies (usually 150) or the basic unit of the Roman army (120).
The example of a fundamentalist group called Schmiedleut Hutterites from North Dakota
showed that this society prefers to split up into two groups rather than exceed a limit of 150 group members. According to Dunbar, “when the number of individuals is much larger than this, it becomes difficult to control their behavior by means of peer pressure alone. [...] Rather than create a police force, they prefer to split the community.”
In another study from 1991 Dunbar shows that the time used for the act of grooming among primates is linear to the group size. Meaning that maintaining social relationships requires grooming, and that the bigger the group is, the more its members have to groom each other. The result is that the time required for grooming in a group of the size described by Dunbar’s Number is 42 % of the total daily time budget (Dunbar, 1991). Because of these results Dunbar develops the hypothesis that language may have evolved to actively substitute a large amount of grooming and therefore facilitate the organization in larger groups.
Based on this hypothesis we are able to develop another one: If technology, such as language allows for greater social networks, does modern digital social network services facilitate an even greater social network?
Of course, this hypothesis only focuses on the quantity of social relationships, not on the quality. Further investigation has to be done to fully understand how technology effects society.
DUNBAR, Robin I. M. (1991). “Functional significance of social grooming in primates”. Folia Primatologica, vol. 57, 121-31.
DUNBAR, Robin I. M. (1993). “Coevolution of neocortical size, group size and language in
humans”. Behavioral and Brain Sciences, vol. 16, 681-735.
CHRISTAKIS, Nicholas A. & FOWLER, James H. (2010). Connected. The Surprising Power of Our Social Networks and How They Shape Our Lives, London, HarperPress.
MCCARTY, C. & KILLWORTH, P. D. & BERNARD, H.R. & JOHNSEN E. & SHELLEY, G. (2000). “Comparing Two Methods for Estimating Network Size”, Human Organization, vol. 60, 28–39.