Friends start out with a lot in common, Facebook data show

The social networking site Facebook is helping researchers answer one of the oldest chicken-and-egg questions about human nature: Do we become friends with people because we have a lot in common to start with, or do we become more like our friends over time as we are influenced by their tastes and preferences? A study published online Monday by the journal Proceedings of the National Academy of Sciences says the first scenario is correct -- at least if we are college classmates at Harvard.

For the study, researchers at Harvard got permission to collect information from the Facebook accounts of all members of the class that enrolled at “a diverse private college in the Northeast U.S.” in the fall of 2005. (That’s the description offered in the 2008 study that first described this unique dataset. There are several other clues that the college in question is Harvard, including the number of students in the class and the academic affiliations of the researchers.)

Nearly all of the students had a Facebook account, but in many cases their privacy settings put their data off limits. In the end, the researchers were able to include 1,001 students whose Facebook friendships were public in the spring of their freshman, sophomore, junior and senior years on campus.

It turned out that students were most likely to befriend others who lived in the same dorm or shared the same major (and presumably took a lot of classes together). For instance, a person in the study was almost twice as likely to friend someone who lived in the same building compared with someone who did not. The researchers also found that one student was 10% more likely to friend another if they already had a friend in common, and the odds increased by another 10% with each additional mutual friend. The net result was that students tended to “self-segregate on the basis of gender, racial background, region of origin, and socioeconomic status,” according to the PNAS study.

The researchers looked at all of the students’ preferences for music, movies and books and found that people whose friends liked classical and/or jazz music were more likely to become fans of classical and/or jazz music too. But that was the only case where tastes were “contagious,” and in this particular case it could be due to the music’s “unique value as a high-status cultural signal,” the researchers wrote.

Generally speaking, students and their friends shared tastes in music and movies. That meant that people who liked “dark satire” films or movies that fit under the heading of “raunchy comedy/gore” were “significantly more likely than chance to become and remain friends,” the researchers found.

So if you thought you could convince your buddies to accompany you to a screening of the latest “Twilight Saga” movie or adopt your enthusiasm for Rush, think again. “Our findings suggest that friends tend to share some tastes not because they influence one another, but because this similarity was part of the reason they became and remained friends in the first place,” the researchers concluded.

In other words, birds of a feather really do flock together.

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