By Antonio A. Casilli (Telecom Paristech ENST - Centre Edgar-Morin EHESS, Paris)

What’s the actual size of your personal social network? Some numbers

Ok, so you have hundreds of friends on Facebook and thousands of followers on Twitter. Big deal. How many will show up to help you win that human pyramid contest, uh? And how many have you actually being interacting with in the last few months? More broadly, what’s the size of your actual social network? Scientists have been looking for an answer to that question, exploring the cognitive limits of the number of individuals one person can create ties with, both online and offline.

Famously, in 1992 anthropologist Robin Dunbar proposed a rough estimate of 150. The ‘Dunbar’s number’ was the result of a large-scale study comparing the size of the neocortex in primates and humans. But in 1998 that figure pretty much doubled when social network analyst Peter Killworth contemplated a mean personal network size of 290. And in 2010 that number doubled again, as sociologist Matthew Salganik settled for an estimate of 610 personal ties.

So who says 1,200? Nobody yet. Maybe (I’m just teasing) psychologist Lisa Barrett will come up with a number of her own, if the hype surrounding her latest article published in Nature Neuroscience continues. What hype? Didn’t you see this?

Apparently, after scanning a few brains, Barrett and her team discovered a fancy correlation between personal network size and the size of the corpus amygdaloideum. Turns out Facebook has nothing to do with the matter in question. If the numbers of the average size of personal networks are going up as years go by, it’s not because of our increasing technological embeddedness. Dunbar’s number was based on the size of human neocortex (i.e. that part of the human brain presiding higher mental functions), so it  would come as no surprise if it was way smaller than the one correlated to the size of the amygdala (the part that regulates emotional responses and aggression). After all, it’s safe to say that among our acquaintances the number of those we would like to punch is higher than that of those with whom we would enjoy a civilized chat…

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ResearchBlogging.org

Bickart, K., Wright, C., Dautoff, R., Dickerson, B., & Barrett, L. (2010). Amygdala volume and social network size in humans Nature Neuroscience, advance online publication DOI: 10.1038/nn.2724

Dunbar, R. (1992). Neocortex size as a constraint on group size in primates Journal of Human Evolution, 22 (6), 469-493 DOI: 10.1016/0047-2484(92)90081-J

Killworth, P., Johnsen, E., Bernard, H. R., Shelley, G., & McCarty, C. (1990). Estimating the size of personal networks Social Networks, 12 (4), 289-312 DOI: 10.1016/0378-8733(90)90012-X

McCormick, T., Salganik, M., & Zheng, T. (2010). How Many People Do You Know?: Efficiently Estimating Personal Network Size Journal of the American Statistical Association, 105 (489), 59-70 DOI: 10.1198/jasa.2009.ap08518


ps. This post was inspired by a few tweets exchanged with mathematician Valdis Krebs (@orgnet) and anthropologist Sally Applin (@AnthroPunk). To them goes my appreciation and #FF.

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