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Do opposites really attract? Despite what you may have grown up hearing, studies may reflect the opposite—interestingly, especially when it comes to looks.

According to research reported in the July 2010 issue of and Social Psychology Bulletin, we are attracted to people who resemble our parents or ourselves.

In one study, subjects were shown pictures of strangers which were preceded by a short glimpse of either their own opposite- parent or a stranger. Subjects exposed to a short glimpse of their parent before being exposed to the target picture were more likely to assign higher ratings of to the person in the target picture. In a second study, a picture of the stranger was morphed with a picture of themselves or a picture of another stranger. When subjects were asked to rate the portrayed people for attractiveness, they usually picked the people who were an amalgamation of a stranger and themselves.

As it turns out, then, we are much more likely to fall for someone who looks like us or our opposite-sex parent. This may indicate that our incest taboos are social constructs instituted to prevent people from following their instincts. However, there are other explanations of why we are attracted to people who look like us.

Researchers at the deCODE company in Reykjavik, reporting in a 2008 issue of Science, found that marriages between third or fourth cousins in Iceland tended to produce more children and grandchildren than those between completely unrelated individuals. The researchers suggest that marrying third and fourth cousins may be optimal for reproduction because this degree of genetic similarity may produce the best gene pool. and first-cousin couples, were they to mate, could have inbreeding problems, whereas couples genetically far-removed from each other could have genetic incompatibilities. Third- and fourth-cousin couples, though, tend to be genetically compatible while having no serious inbreeding problems.

At first glance, such findings seem to go against the so-called "Westermarck effect," which posits that people who grow up together are disposed not to fall in love with each other after they reach sexual maturity. But the Westermarck effect—based on a series of studies done by Finnish anthropologist Edvard Westermark—actually is consistent with the recent findings—living in close proximity is no doubt the decisive factor for in terms of sexual , not the degree of the individuals' resemblance.

In fact, the Westermarck effect has been confirmed, in the Israeli kibbutz system of communal living, in which people who grow up together are typically not directly related to each other and do not look alike. And consider how traditional sim pua marriages, mostly dating from pre-modern Taiwan, also confirm Westermarck’s theory: Sim pua means “little daughter in-law." In the system, a female infant is given to a family to be reared as their own daughter. When she grows up, she is to marry a son in that family. But sim pua marriages have produced a low fertility rate, a high rate, frequent , and lack of sexual attraction. In some cases, the son or "daughter-in-law" has refused to marry their destined-for spouse.

So, the degree to which a couple resembles each other could be a defining factor in relationship satisfaction after all.

Source: lovesicklove.com, used with permission

Berit "Brit" Brogaard is the author of On Romantic Love