Finding Your Crowd

New acquaintances are easy to "friend" but just as easy to forget. How do we decide who's truly friendship material? Superficial connections like going to school together or rooting for the same team can get things off the ground, but there are other, more covert social dynamics at play.

Someone Like You

We gravitate toward people who resemble us and come from similar backgrounds—researchers call this homophily. Social network experts Nicholas Christakis and James Fowler have found that, even controlling for ethnicity, friends have similar genomes: Compared to strangers, friends in a large sample were, on average, as genetically similar as fourth cousins. Further exposing the role of likeness, Wellesley College psychologist Angela Bahns and colleagues determined that even new friends were more similar than nearby strangers in their attitudes about politics, exercise, loud music, and much more.

Barriers to Entry

Friends who reported longer and closer bonds were no more alike than those with less established ones, Bahns's study showed, suggesting that the selection of like-minded companions, more than long-term social influence, accounts for the similarities. "Whatever people rate as important," Bahns says, "they tend to match friends more closely on that thing." Yet friends held comparable attitudes whether or not they recalled discussing them. How does sorting happen? One possible explanation is that we use minimal details and visual cues to infer similarity. Volunteers in another study showed a propensity to pick conversation partners who were similar to them—but if everyone's torso area was covered with a plastic bag, this similarity seeking disappeared.

Branching Out

"We prefer similarity most of the time," Bahns says, but not in every domain. Friends in her study tended to be more closely matched than strangers on the personality trait of agreeableness but not on neuroticism, which includes such characteristics as hostility and depression. Personality traits can shape our friendships in other ways. "People who have high openness to experience move around more and have a much wider selection of experiences," says Finnish cognitive scientist Michael Laakasuo. A recent study that he and others conducted indicates that such people are more likely to have close friends who live farther away and whom they see less frequently, while those low on the trait of openness are more likely to list relatives as friends.

Overthinking It

Striving to land on the best choice, or maximizing, has been linked to dissatisfaction in romantic relationships as well as in other contexts—including friendship. In choosing people to hang out with, recent studies found, those who struggled with their decisions and dwelled on alternatives also tended to report higher levels of negative feelings. Though it's not clear whether these behaviors cause adverse outcomes or coincide with them for another reason, the results show that "if you maximize when selecting your friends, you are also more likely to regret those decisions, and we think that lowers well-being," says University of Southern California's David Newman. Every friendship has pluses and minuses, and we may overthink them at our own risk.

Facebook image: Liderina/Shutterstock