Just one in two would actually consider you their own buddy - meaning friendship is not a two way street.
And this inability to know who our real friends are limits our powers of persuasion, say scientists.
Dr Erez Shmueli, of Tel Aviv University, said: “It turns out we are very bad at judging who our friends are.”
He added: “We found 95 percent of participants thought their relationships were reciprocal.
“If you think someone is your friend, you expect him to feel the same way. But in fact that is not the case. Only 50 percent of those polled matched up in the bidirectional friendship category.”
The study published in PLoS One found people have a very poor perception of social ties, and this limits their ability to influence their ‘friends’.
It could help companies and groups that depend on social influence for collective action, information dissemination and product promotion improving their strategies and interventions.
Explained Dr Shmueli: “Our difficulty determining the reciprocity of friendship significantly limits our ability to engage in cooperative arrangements.
“We learned we can’t rely on our instincts or intuition. There must be an objective way to measure these relationships and quantify their impact.”
The researchers conducted extensive social experiments and analysed the data from other studies to determine the percentage of reciprocal friendships and their impact on human behaviour.
The they also examined six surveys from some 600 students in Israel, Europe and the United States to assess friendship levels and expectations of reciprocity.
They then developed an algorithm that examines several objective features of a perceived friendship, such as the number of common friends or the total number of friend.
This was able to distinguish between the two different kinds of friendship, unidirectional or reciprocal.
The researchers found their ‘friendship algorithm’ determined with an extremely high level of accuracy the reciprocal or unidirectional nature of a friendship.
Added Dr Shmueli: “Our algorithm not only tells us whether a friendship is reciprocal or not. It also determines in which direction the friendship is ‘felt’ in unilateral friendships.”