We are bad judges of friendship: study

Only half of the people you think are your buddies consider you their friend, according to a new study which suggests that people have a very poor perception of friendship ties.
"It turns out that we are very bad at judging who our friends are," said Erez Shmueli from Tel Aviv University in Israel.
"And our difficulty determining the reciprocity of friendship significantly limits our ability to engage in cooperative arrangements," said Shumeli, who conducted the study in collaboration with researchers from Massachusetts Institute of Technology in the US.
"We learned that we cannot rely on our instincts or intuition. There must be an objective way to measure these relationships and quantify their impact," he added.

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.
They examined six friendship surveys from some 600 students in Israel, Europe and the US to assess friendship levels and expectations of reciprocity.

They then developed an algorithm that examines several objective features of a perceived friendship (that is, the number of common friends or the total number of friends) and were able to distinguish between the two different kinds of friendship - unidirectional or reciprocal.
"We found that 95 per cent of participants thought that their relationships were reciprocal. If you think someone is your friend, you expect him to feel the same way," said Shumeli.

"But in fact that is not the case - only 50 per cent of those polled matched up in the bidirectional friendship category," he said.
"Reciprocal relationships are important because of social influence. In this experiment that analyses different incentives for exercising, we found that friendship pressure far outweighed money in terms of motivation," said Shumeli.
"We found, not surprisingly, that those pressured by reciprocal friends exercised more and enjoyed greater progress than those with unilateral friendship ties," he said.
Researchers found that their "friendship algorithm" determined with an extremely high level of accuracy the reciprocal or unidirectional nature of a friendship.

"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," said Shumeli.
The findings were published in the journal PLoS One.