PARIS - People cannot have 1,000 real friends on Facebook. Nor 500. In fact, anything over 200 starts seeming unlikely, an unusual study asserted yesterday.
Limitations on brain capacity and free time means 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," Professor Dunbar told Agence France-Presse.
"It is as though we each have a limited amount of social capital and we can choose to invest it thinly in more people or thickly in fewer people. But you can't exceed these limits."
People have, on average, five intimate friends, 15 best friends, 50 good friends, 150 friends, 500 acquaintances and 1,500 persons whom they recognise on sight.
The scientist added: "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.
"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 does not distinguish between types of friendship, Prof Dunbar pointed out.
For the new study, he used data from two polls targeting over 3,300 people in Britain.