Though "variety is the spice of life" and "opposites attract," most people marry only those whose political views align with their own, according to new research from Rice University and the University of Nebraska-Lincoln. Political scientists found that political attitudes were among the strongest shared traits and even stronger than qualities like personality or looks.
In an article published in the April issue of the Journal of Politics, researchers examined physical and behavioral traits of more than 5,000 married couples in the United States. They found spouses in the study appeared to instinctively select a partner who has similar social and political views.
"It turns out that people place more emphasis on finding a mate who is a kindred spirit with regard to politics, religion and social activity than they do on finding someone of like physique or personality," said John Alford, associate professor of political science at Rice University and the study's lead author.
On a scale of 0 to 1, where 1 means perfectly matched, physical traits (body shape, weight and height) only score between 0.1 and 0.2 among spouse pairs. Personality traits, such as extroversion or impulsivity, are also weak and fall within the 0 to 0.2 range. By comparison, the score for political ideology is more than 0.6, higher than any of the other measured traits except frequency of church attendance, which was just over 0.7.
The study adds to recent "sorting research" that has uncovered a surprising level of uniformity in Americans' personal political communication networks -- where they live, with whom they socialize and where they work.
The new research shows that this sorting doesn't stop with the selection of neighborhoods or workplaces, however. It's also visible in choice of spouses, Alford said.
"It suggests that, perhaps, if you're looking for a long-term romantic relationship, skip 'What's your sign?' and go straight to 'Obama or Palin?'" Alford said. "And if you get the wrong answer, just walk away."
Alford and his co-authors noted that sorting is not the only reason for spouses' political uniformity, but it is clearly the most powerful. More traditional explanations for the political similarity of spouses turned out to have only modest effects and account for only about 10 percent of the similarity between long-term partners. Social homogamy -- or the tendency for people to choose a mate from within one's own religious, social, economic and educational surroundings -- played only a small role.
Similarly, the researchers found little support for interspousal persuasion, the notion that partners tend to adapt to one another's political beliefs over time – a discovery that could have implications on partisan politics for generations to come, the researchers said.
"We did expect to find a strong political bond between husbands and wives," said John Hibbing, a professor of political science at the University of Nebraska-Lincoln and a co-author of the study. "But we were surprised that political concordance seems to exist from the very early years in the marriage, instead of the folk wisdom of mates growing more alike politically as their relationship goes along."
The authors said this sorting can have a big impact on the future of American politics: If parents transmit political traits to their children, then the practice of liberals marrying liberals and conservatives marrying conservatives seems likely to increase political uniformity into the next generation.
"Obviously, parents are very influential in shaping the political beliefs of their children," Hibbing said. "If both parents are on the left or on the right, it makes it more difficult for a child to be something different. It may be part of the reason why we see such polarization."
This means that marriage -- a major means by which diversity enters into extended families --doesn't actually contribute much to the political "melting pot," Alford said.
"Instead, marriage works largely to reinforce the ongoing ideological polarization that we see so clearly today," he said.