Why do people have best friends? Why do we think of some individuals as “better” friends than other individuals? Why rank friends at all? And what is so special about the apex of the ranking, our “best” friend?
Peter DeScioli, a Kay Fellow at Brandeis University, and colleagues recently shed light on these questions by collecting a dataset of over 10 million people’s friendship decisions from the MySpace social network. The results support the “alliance hypothesis” which is based on the idea that people depend on their friends in conflicts. The findings were recently published in the journal Perspectives on Psychological Science.
MySpace has a feature that allows users to rank their “Top Friends,” providing a unique data source for testing how well different variables explain people’s rankings of friends. The alliance hypothesis predicts that people will feel closest to friends who rank them higher than others. Here’s why: If you need your friend to take your side in an argument, then they will have to side against someone else—which is unlikely if they are better friends with your adversary. The fewer people ranked above you, the more you can rely on your friend to take your side. According to the theory, people unconsciously track this strategic information and it shapes how we feel about our friends.
It turns out that the importance of friend rank was highly significant. Comparing first- and second-ranked friends, 69% chose for first-rank the individual who ranked them better. This was a considerably larger effect than the next best predictor, geographic proximity. The effects of sex, age, and popularity were small by comparison. Moreover, friend rank increased in strength when the analysis was extended to first- versus third- through eighth-ranked friends. In short, we now have 10 million more reasons to wonder if human friendship might be more strategic than it seems.