Studying the factors that bring people together creates a serious challenge for researchers. Do friendships form because of shared interests, or do those interests develop due to the friendship? A research team has now tracked a set of college students across all four years, using Facebook to identify social ties. The study reveals that people are fundamentally a bit lazy, as proximity provided the strongest predictor of social ties. Once that was accounted for, however, shared tastes in music and film did promote friendships, while books had a minimal effect.

When it comes to being influenced by their friends, the students generally weren't. The exceptions were two genres of music: people liked classical and jazz pieces found via their friends, and those with interests in alternative music acted just like stereotypical hipsters, shying away from things that were popular with their friends.

The study relied on a database (described here) built by following a class from the moment that it entered college at an unnamed university. Each year, the researchers tracked the students' friends and favorite items on Facebook, and linked that information to data provided by the university on the students' majors and housing. (The data was anonymized, and couldn't be traced back to individual students.)

Over 1,600 students started in the study population, but not all of them were available for some aspects of this study. Many had not listed a favorite movie or book, and some had their privacy settings arranged so that the information was not public, and therefore off-limits to the researchers. In fact, the students generally increased the information they kept private over the course of the study, limiting the amount of data available at different time points.

Still, the researchers ended up with a few hundred students each for known social connections and information on movies, books, and music. Matching items were identified, and things were clustered based on genre (ie: pop, classical/jazz, hip hop, etc.). Information on housing, majors, and social connections were included, and a statistical model was built to analyze the results.

On the most basic level, shared tastes had nothing on convenience. Ending up in the same building increased the odds that people would establish and maintain a Facebook connection over the four years of college. Being the same major also boosted the odds, though not by as much. Shared friendships also provided a boost, with each additional friend strengthening the effect.

In contrast, shared tastes had a minimal effect, one that was insignificant for most genres, and small for the few cases it was significant. For music, the significant influences were classical/jazz and classic rock; for movies, satires and raunch/gore were the two genres that seemed to cement friendships. Books seemed to have absolutely no effect, although that could be a product of the students having focused their reading on course materials.

When it comes to forming our own tastes, the students generally tended to ignore their friends. Still, there were two exceptions. People seemed to pick up on classical/jazz works their friends liked, presumably because these works don't have a high level of exposure within the college crowd (although the authors explain this by saying that these works have a "unique value as a high-status cultural signal"). In contrast, those whose tastes were more aligned with alternative/indie acts tended to lose interest in songs if they were popular among their friends.

The authors recognize that a Facebook friend probably doesn't represent the strong social bond that we typically view as a friendship, but it is probably similar to the sort of fluid links that many of us form at work and elsewhere. There's also a risk that at least some of the choices revealed on Facebook are the product of social posing, rather than deep-seated preferences. Despite these limitations, the study is a rare look at how social dynamics and personal tastes influence each other over the course of some very formative years. It'll be pretty difficult to arrange a study that provides a clearer picture.

PNAS, 2011. DOI: 10.1073/pnas.1109739109 (About DOIs).