How many friends do you think you have? A hundred, twenty… two? Chances have it, you actually have only half as many ‘real’ friends as you think. At least, those who look to you as a friend too, say researchers at MIT’s Media Lab.

Credit: NBC

The authors surveyed 84 undergrads from the same class with a simple questionnaire. Each participant had to rate every other person in the class from 1 to 5, where 1 is “I do not know this person” and 5 is “One of my best friends”. If the participant rated a person with 3, that qualified as friendship.

Each participant also had to guess how other participants would rate them.

In total,  1,353 cases of friendships or instances where a person was rated with at least 3 on the scale were recorded. In 94 percent of these instances, the participant guessed the other person felt the same. In reality, just 53 percent of these friendships were reciprocal.

“In contrast to the high expectations of reciprocity among the participants, we find that almost half of the friendships are actually non-reciprocal. We show this by constructing a directional friendship network based on explicit friendship nominations (i.e., closeness scores >2). In this network, we consider a friendship tie to be “reciprocal” when both participants identify each other as friends. Alternatively, the tie is “unilateral” when only one of the participants identifies the other as a friend. The final directed friendship network consists of 84 nodes (i.e., participants) and 775 edges (i.e., explicit friendships). Examining the relationship between the reported friendship scores on the two sides of these edges reveals a relatively weak correlation (r = 0.36, p = 0). Furthermore, only half (i.e., 53%) of these edges are indeed reciprocal (413 out of 775),” the researchers write in  the journal PLoS One.

Now, the study itself boasts some obvious limitations starting from the sampling size, to the fact that we’re talking about freaking undergraduates whose friendships can be made or broken at a whim. However, these results were consistent with other surveys on friendship networks some which included as many as 3,160 participants.

“We find this result to be consistent across many self-reported friendship networks that we have analyzed: only 45% (315 out of 698) of friendships are reciprocal in the Friends and Family dataset, 34% (28 out of 82) in the Reality Mining dataset, 35% (555 out of 1596) in the Social Evolution dataset, 49% (102 out of 208) in the Strongest Ties dataset, and 53% (1683 out of 3160) in the Personality Survey. The first three surveys were collected at an American university, the fourth at a European university, and the latter at a Middle Eastern university”

“These findings suggest a profound inability of people to perceive friendship reciprocity, perhaps because the possibility of non-reciprocal friendship challenges one’s self-image,” the study authors conclude.

This might just be the saddest study in social psychology I’ve read all year, or is it? Knowing who your real friends are is important and will save you a lot of trouble. If this study reflects reality, then most of us judge friendships poorly, so maybe now’s a good time to assess who you can count on.