A new Oxford study suggests, People cannot have more than 200 'genuine' friends on Facebook as the constraints that limit the number of friends we have offline also apply online.
Offline, research has given rise to the 'Social Brain Hypothesis' which says that our brain's ability to process multiple relationships creates a natural group size for humans of 100-200 people.
This size is also constrained by the time required to maintain relationships - we only have so much time to devote to meeting or talking to people, researchers said.
It has been suggested that social media might overcome the constraints because posts, tweets and pictures allow us to talk to many more people at the same time even if the interaction is not direct.
Researchers carried out two surveys of more than 3,300 people to see whether using the internet really means we can have more friends.
They found that even among regular social media users, the average number of friends they had on Facebook was 155 in the first survey and 183 in the second, right in the bracket predicted by the Social Brain Hypothesis.
Women had more friends than men (in the first sample, women averaged 166 and men just 145 friends; in the second, it was 196 vs 157) while - perhaps unsurprisingly - older generations had fewer friends than younger ones, Dunbar found.
According to him, social media certainly help to slow down the natural rate of decay in relationship quality that would set in once we cannot readily meet friends face-to-face.
"But no amount of social media will prevent a friend eventually becoming 'just another acquaintance' if you don't meet face-to-face from time to time," Dunbar explained in a paper published in Royal Society Open Science journal.
"There is something paramount about face-to-face interactions that is crucial for maintaining friendships. Seeing the white of their eyes from time to time seems to be crucial to the way we maintain friendships," he added.
