We are bad judges of friendship, new study shows

Their new joint study says only half of your buddies would consider you their own friend. People have a very poor perception of friendship ties, and this limits their ability to influence their "friends," according to the research, published in PLoS One on March 22, 2016.

If researchers can understand this limitation, companies and social groups that depend on social influence for collective action, information dissemination and product promotion could improve their strategies and interventions.

A friend indeed?

"It turns out that we're very bad at judging who our friends are," says Dr. Erez Shmueli, who conducted the study with Dr. Laura Radaelli, both of TAU's Department of Industrial Engineering, in collaboration with Prof. Alex Pentland and Abdullah Almatouq of MIT. "And our difficulty determining the reciprocity of friendship significantly limits our ability to engage in cooperative arrangements. We learned that 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 analyzed the data from other studies to determine the percentage of reciprocal friendships and their impact on human behavior. The team also examined six friendship 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 (that is, the number of common friends or the total number of friends) and is able to distinguish between the two different kinds of friendship: unidirectional or reciprocal.

"We found that 95 percent of participants thought that their relationships were reciprocal," Dr. Shmueli says. "If you think someone is your friend, you expect him to feel the same way. But in fact that's not the case -- only 50 percent of those polled matched up in the bidirectional friendship category."

A matter of influence

Why is this important? According to Dr. Shmueli, influence is the name of the game.

"Reciprocal relationships are important because of social influence," says Dr. Shmueli, who utilized the "FunFit" social experiment in the course of the research. "In this experiment that analyzes different incentives for exercising, we found that friendship pressure far outweighed money in terms of motivation. We found, not surprisingly, that those pressured by reciprocal friends exercised more and enjoyed greater progress than those with unilateral friendship ties."

The 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," Dr. Shmueli says.