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MONDAY, June 30 (HealthDayNews) -- If you want to know the kind of partner you're looking for, try looking in the mirror.

Researchers at Cornell University have concluded people look for mates who have traits, physical and otherwise, that are similar to their own.

These findings, which appear in this week's issue of the Proceedings of the National Academy of Sciences, differ markedly from the so-called "parental investment" theory of mate selection, which posits that people pick partners who possess qualities important to successful child-rearing.

Other experts, however, don't agree with how the study was done.

"Just because they [the study participants] tell you they are attracted to people who have those attributes doesn't mean they would actually choose those people," says Kate Wachs, a Chicago psychologist and author of Relationships for Dummies. "Self perception is very different."

The researchers asked 978 college-age heterosexual men and women to fill out a two-part questionnaire. The participants were all located in the Ithaca, N.Y., area and many were students at Cornell.

The first part of the questionnaire required the respondents to rate the importance of 10 different qualities in a potential life partner. The qualities were grouped into four "evolutionarily relevant" categories: wealth and status, family commitment, physical appearance and sexual fidelity.

In the second part of the questionnaire, the respondents rated their own perceptions of themselves for each of these same attributes.

A clear pattern emerged from the responses: People who indicated that a particular attribute was important in a partner tended to rate themselves highly in that same category.

There is one possible methodological problem with this system, says Arthur Aron, a professor of psychology at the State University of New York (SUNY) Stony Brook: The fact that people first rated how important each of the attributes was in a partner may have influenced how they rated themselves.

Regardless, Aron, unlike Wachs, believes the findings are sound.

"The results were extremely clear and strong. They were strikingly powerful results," he says.

Which is not to say that life is ever that simple.

"A simple, summary statement like opposites attract or similars attract is always going to be fundamentally flawed and wrong part of the time," asserts Michael Cunningham, a psychologist in the department of communications at the University of Louisville in Kentucky. "It's always impossible to summarize the process of mating in a single principle."

For example, the "opposites attract" rule has many exceptions, Cunningham notes. A poor person is likely to be attracted to his or her opposite, for instance, but a rich person is not likely to be attracted to a pauper.

It's the same with looks: "Very seldom does Beauty love the Beast," Cunningham says.

On the other hand, outgoing people tend to like other outgoing people, quiet people tend to be attracted to quiet people, and smart people tend to gravitate towards other brainy types, Cunningham says.

With respect to the most obvious difference in the mating process, 90 percent or more are attracted to their opposite.

It's also important not to confuse personalities with behavior and experience, Aaron adds. "For the most part, opposites attracting in terms of different personalities or backgrounds or attitudes occurs only under very specialized conditions," he says.

All this discussion doesn't even begin to address what works in a real-life relationship. And here the study authors may be on to something.

"Even though opposites can attract initially, it's usually the similarities that pay off more," Wachs says. "You might be attracted to somebody who's totally different from you, but in the end it's not going to work."

More information

For more on relationships and what makes them work, visit drkate.com or the American Psychological Association.