Paris, January 20

People cannot have 1,000 real friends on Facebook. Nor 500. In fact, anything over 200 starts seeming unlikely, an unusual study asserted today. Limitations on brain capacity and free time meant that humans can nurture no more than about 150 true friendships on social media, just as in real life, said a paper in the journal Royal Society Open Science. The rest are acquaintances, or people recognised on sight.

A theoretical limit of 150 friends has become known as “Dunbar’s Number” after British evolutionary psychologist Robin Dunbar, who coined the concept. He also authored the new study, and concluded the same limits applied online.

“There is some flexibility, perhaps, but not very much, and it mostly depends on how weak or strong you want your friendships to be,” Dunbar told AFP.

Dunbar believes human relationships are layered in ever larger circles from closest to furthest.

We have on average five intimate friends, 15 best friends, 50 good friends, 150 friends, 500 acquaintances and 1,500 people we recognise on site.

“The 150-layer is the important one: this defines the people you have real reciprocated relationships with, those where you feel obligations and would willingly do favours,” the scientist explained.

“People can (and sometimes do) have 500 or even 1,000 friends on Facebook, but all they are doing is including people who we would normally call acquaintances or people we just recognise by sight but don’t know very well.”

Facebook didn’t distinguish between types of friendship, Dunbar pointed out.

Psychologists like Dunbar believe friendship limits are determined by two things: the ability of our brain to process multiple relationships, and time limitations.

For the new study, Dunbar used data from a two polls targeting more than 3,300 people in total in the United Kingdom. The first group had 155 Facebook friends on average, and the second about 183.

When asked how many of their Facebook friends they could turn to for support in a crisis, people responded four. Asked how many they could go to for sympathy, the answer was 14 -- echoing the pattern of real-life friendship layers.

“We should be careful not to include professional users such as journalists, congressmen, writers, singers etc, as they use Facebook as a kind of free fan club -- it doesn’t matter to them whether they really know these people or not.”