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Casey A. Klofstad of the University of Miami, Rose McDermott of Brown University and P.K. Hatemi of Pennsylvania State University explore a different possible reason for the increased political polarization: dating. In a 2013 study published in Political Behavior, "The Dating Preferences of Liberals and Conservatives" (open version here), the authors use a random sample of about 3,000 online dating profiles to determine whether "positive mate assortation -- like seeks like -- on nonpolitical factors such as lifestyle and demographics could lead to inadvertent assortation on political preferences."

Building on prior scholarship that demonstrates a link between the political preferences of parents and their children, the researchers test the hypothesis that "spousal concordance on political preferences could be due to mates seeking others who are similar to themselves on traits related to ideology."

Study findings include:

Although the profiles do not place heavy emphasis on politics, "daters appear to sort on other traits, which correlate with ideology. As such, individuals may find their ideological matches by assorting on characteristics informed by the social environments where individuals reside, and these traits are related to political preferences in undefined yet systematic ways."

With a few exceptions, both liberals and conservatives in the sample generally preferred to date people like themselves: "Positive assortion behavior is pervasive."

Some cases were found in which liberals and conservatives take different dating approaches. For example, conservatives are more likely than liberals to want to date someone who shares their relationship status and views on tobacco usage, while more progressively minded daters are more willing to date someone with a different body type than their own.

"If all things remain constant, the number of individuals in [the] extreme left and right ideological tails will be almost 2 times greater in 5 generations and 2.5 times greater in 25 generations merely as a result of assortive mating."

The authors conclude that the "increasing prevalence of Internet dating may hasten the process of assortation, and potentially political polarization as well, as individuals can easily select potential mates that are similar to themselves by searching through detailed profiles before investing the time and energy involved with courtship.

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