(PhysOrg.com) -- According to Oxford University's professor of evolutionary anthropology, Robin Dunbar, after you have amassed 150 friends on Facebook, any more are meaningless because the human brain can only remember 150 meaningful relationships anyway. Professor Dunbar says this number applies to different societies and has remained unchanged throughout history.

In the 1990s Professor Dunbar developed a theory that the volume of the neocortex, the part of the brain involved with language and conscious thought, can only manage active relationships with around 150 friends — Dunbar’s Number — regardless of how many friends a person has either online or offline. On sites like Facebook, MySpace and Bebo, it is easy to collect 1,500 “friends” or more, but Dunbar said that when you examine the traffic, people maintain relationships only with an inner circle of no more than 150 people, as they do outside the online environment.

Dunbar reached the value of Dunbar’s number by studying a wide range of societies throughout history, including social circles from Neolithic and Roman times, to the modern office, and in non-human primates. The value of 150 is an approximation and there is no precise value, but Dunbar found that social groups larger than around this number tended to splinter.

Professor Dunbar’s findings are backed up by Cameron Marlow, a research scientist with Facebook, who said last year he had found Facebook users only communicate regularly with a small core of their listed friends.

In a study to be published later this year, Professor Dunbar applied his theory to Facebook to find out if Dunbar’s Number was exceeded in the online environment. To do this, he compared the traffic at the site of people with thousands of friends to those with hundreds or less, and found there was no discernible difference between them.

His findings suggest Dunbar’s Number is not exceeded, and the brain cannot expand its ability to have meaningful relationships with more people, even in the virtual world. Dunbar defined a meaningful relationship as one in which you contact people at least annually, and in which you understand the relationships between the person and others in your circle of friends.

Dunbar’s findings also showed women were better than men at maintaining Facebook relationships, which Dunbar said suggested women could relate to friends just by “talking” to each other, while males need to “do physical stuff together.”

Psychologists warning that sites like Facebook produce insecurity through encouraging a “friendship addiction,” or an urge to amass a large number of friends to prove people are popular, will no doubt welcome Professor Dunbar’s findings.

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More information: References:

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

Dunbar, R.I.M. (1993), Coevolution of neocortical size, group size and language in humans, Behavioral and Brain Sciences 16 (4): 681-735.

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