In friendship, as in much of life, the rule tends to be that birds of a feather hang together. Sociologists call this homophily, or “love of the same,” and they have persuasively argued that it accounts for why people of the identical class, race, education, and gender associate with one another. “Similarity breeds connection,” wrote University of Arizona sociologist Miller McPherson and his colleagues in a seminal 2001 paper, so “people’s personal networks are homogeneous with regard to many sociodemographic, behavioral, and intrapersonal characteristics.” Opposite don’t attract: We marry and hire the people that remind us of ourselves. For better, and in the case of social stratification, worse.
All of which makes a new study in Social Psychological and Personality Science so compelling. A research team led by University of Helsinki researcher Michael Laakasuo dug into people’s personalities related to their friendships. The data set was over 12,000 people participating in a long-term British survey who answered questions about the characteristics of their friends — like their ethnicity, where they lived, how often they saw each other — and took a Big 5 personality assessment. (The Big 5 is the leading and highly validated model of human personality. The traits are extroversion, or how much you love being around people; neuroticism, or how sensitive you are to events and how much you ruminate on them; conscientiousness, or how much you need to show up to appointments on time; agreeableness, or how warm and personal you are with people; and openness to experience, or how curious you are to eat new foods, go to new places, and think new thoughts.) On average, the participants averaged 2.8 close friends apiece: 86 percent had three, 8 percent had two, and 6 percent had one. In this data set — all people living in the U.K. — most friends lived within five miles of each other, and they hung out weekly or daily. The age difference averaged under two years, and 74 percent of the friends weren’t also relatives.
To students of humanity, some of the personality-based findings are pretty intuitive: People with low extroversion, conscientiousness, and openness were most likely to have just one friend. Those with a lot of agreeableness had “more traditional friendship ties”: living close to their best buds, and knowing them for longer. Extroversion related to seeing your bros or gals more often; conscientious people had fewer unemployed or student friends (!) and were more likely to have friends of their same sex, as were people who scored low on neuroticism. Then there was trait with the “most idiosyncratic pattern of friendships”: openness to experience.
The rambling men and women who scored high on openness tended to have “less traditional” friendships: seeing them less often, living further from them, and having buds that were less likely to be relatives. They were also more likely to have pals of another ethnic group or gender. While the researchers recognized that people with low openness were just 2 percent less likely to have an opposite-sex or different-ethnicity friend, they argue that the sample of 12,000 respondents and 33,000 friends is large enough to detect “small effect sizes,” which have been a bit of a bugbear within social science.
Why are the openness folks such inclusive weirdos? Laakasuo and company point to a couple of pieces of research: Openness is associated with lower stability in friend relationships, more moving from one city to another, and a higher likelihood of making friends through the magic of the internet. Then there’s this elephant in the room: The more open you are to experience, the less likely you’re racist.