Fewer than three per cent of Facebook friends can be relied on to help in a crisis, according to a new Oxford University study.
Psychologist Professor Robin Dunbar carried out two surveys of more than 3,300 people to see whether using the internet really means we can have more friends.
Prof Robin Dunbar said: "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.
"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."
Prof Dunbar 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.
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.
The first survey group, made up of regular social media users, considered only 28 per cent of their Facebook friends to be genuine friends.
When asked specifically how many people they would turn to for support in a crisis and how many they would turn to for sympathy, on average those groups were just four and 14 friends respectively.
The paper is published in Royal Society Open Science.