Ever wonder how you ended up with the friends you have? Well, you aren’t the only one – several psychologists have asked this same question, and tried to answer it with scientific studies.

Generally, it appears that people choose tend to choose friends with similar personality traits. For example, a recent survey of 46,483 people found that on average, friends had significantly more shared personality traits than non-friends. This finding led the researchers to conclude that “birds of a feather do flock together.”

Other studies have tried to get specific about what personality traits friends tend to share.

A 2010 study of first-year university students came up with a couple interesting results. First, it found that some personality traits are conducive to building friendships in general. Specifically, people who are more extraverted tend to initiate more friendships while people who are more agreeable tend to have other people initiate more friendships with them – neither of which is necessarily a big surprise.

The study also found that people tend to select friends who are similar to them on three personality traits: extraversion, agreeableness and openness. So, for example, people who are disagreeable will tend to select disagreeable friends, and vice-versa.

That said, some friends seem to be more similar than others. Research published last year showed that friends who had similar levels of narcissism tended to have similar levels of other personality traits – and friends who differed in terms of narcissism also tended to differ in terms of other traits. This result prompted the authors of the paper to revise the old saying and declare that “narcissists of a feather flock together.”

Of course, just because we often select friends who share our personality traits doesn’t mean it’s a good idea to only be friends with people exactly like us – sometimes the friendships with people who give us a different perspective are the most interesting! All else being equal, though, it appears that we default to “flocking together with birds of a feather” more often than not.

Image: Flickr/Stella Dauer under CC BY-SA 2.0