Everything Is Obvious_ _Once You Know the Answer - Duncan J. Watts [114]
Recently my former graduate student Gueorgi Kossinets and I used exactly this kind of approach to study the origins of homophily within the students, faculty, and staff of a university community. As with previous studies, we found that acquaintances—meaning people who exchanged e-mail on a regular basis—were considerably more similar on a range of attributes such as age, gender, academic major, and so on than strangers. We also found that similar people who were not acquainted were more likely than dissimilar people to connect to each other over time—just as common sense would contend. Finally, however, we found that individuals who were already “close” to each other, either because they shared mutual friends or belonged to the same groups, were more similar than distant pairs, and that most of the bias toward connecting similar individuals disappeared once we accounted for the effects of proximity. Our conclusion was that although the individuals in our community did exhibit some preference for others who were similar, it was a relatively weak preference that had been amplified over time, by successive “rounds” of choices, to generate the appearance of a much stronger preference in the observed network.18
Another problem to do with homophily that the Internet may help to answer is one that political scientists and sociologists have long worried about—namely, that Americans, whether by choice or by circumstance, are increasingly associating with like-minded neighbors and acquaintances. If true, the trend is thought to be problematic, as homogeneous social circles can also lead to a more balkanized society in which differences of opinion lead to political conflict rather than exchanges of ideas among equals. But is there actually any such trend? Political scientists generally agree that Congress is indeed more polarized now than at almost any point in history, and that the media is not much better. However, studies of polarization among ordinary citizens have tended to reach conflicting conclusions: Some find that it has increased dramatically while others point to levels of agreement that have changed little in decades.19 One possible explanation for these contradictory results is that people think that they agree with their friends much more than they actually do; thus much of the polarization may be perceived rather than real. But testing this hypothesis, although simple in theory, is difficult in practice. The reason is that in order to measure whether friends agree as much as they think they do, one would need to ask, for every issue of interest, and for every pair of friends A and B, what A thinks about the issue, what B thinks about the issue, and what A thinks B thinks about it. Do this for lots of issues and many pairs of individuals, and you have a tremendously laborious survey exercise, especially if you also have to get each respondent to name friends and then go track them down.20
On Facebook, however, it’s relatively straightforward. Everyone has already declared who their friends are, and it’s even possible to differentiate different strengths of friendships, by counting how many mutual friends they share.21 Equally important, in 2007 Facebook launched their third-party developer “platform,” which allowed outside programmers to write their own applications that would then “run” on Facebook’s