By CATHERINE RAMPELL

DESPITE THE OLD saying “opposites attract,” scholars have found that in almost every way imaginable, people tend to choose mates who look, sound and act as they do.

But in the area perhaps most fraught with potential conflict - money - somehow, some way, people gravitate toward their polar opposite, a new study says.

“Spendthrifts” and “tightwads” (which, as it turns out, are actual academic terms) tend to marry the other. Unfortunately, these disparate duos report unhappier marriages than people with more similar attitudes toward spending.

How do we know all this? Researchers at the University of Pennsylvania, the University of Michigan and Northwestern University in Illinois looked at several surveys that asked a married couple to assess separately their personal feelings toward spending money.

Respondents were then rated on a Tightwad-Spendthrift scale. The labels refer not to how much people earn or spend, but how people described their feelings about spending.

Spendthrifts, on this scale, say they experience too little pain when spending, leading them to spend more than they should; they later regret their financial recklessness.

Tightwads, by contrast, report feeling too much pain when spending. They have trouble parting with their pennies, and yet they frequently kick themselves for having so much difficulty living life. In other words, they live in a perpetual state of nonbuyer’s remorse.

From such differences, love blossoms (at least to a modest but statistically significant degree, the study found).

“Almost all prior research has found that birds of a feather flock together,” said Scott I. Rick, a University of Michigan marketing professor who is a coauthor of the study. “People have tried to find evidence of complementarity, but they usually can’t.” The major exception to that rule is dominant versus submissive personalities, traits for which opposites do tend to attract.

Why do people seek out their opposites in spending attitudes? Most likely, what we hate in ourselves, we also hate in other people. And the more we hate that quality in ourselves, the more we avoid it, the study suggested.

“I can see how this might be one of those kinds of seductive differences in the early stages of courtship,” said Stephanie Coontz, a professor at Evergreen State College in Olympia, Washington, and research director for the Council on Contemporary Families. “Maybe you say to yourself, ‘This guy makes me feel so free,’ or ‘This gal reins me in.’”

Yet, as previous studies found, spending decisions are a common source of marital conflict and a major contributor to divorce. And as prior literature would predict, this new study showed that financially polar pairs report greater conflict over money, and lower levels of connubial bliss.

It appears that people are aware of this potential for conflict. In another set of surveys, the authors asked unmarried people about their ideal mates. The answers generally described a spouse who would be identical to them on consumption concerns: the more these unmarried survey respondents said they disliked spending money, the more they thought their soul mates should also dislike spending money, and vice versa.

Perhaps this disconnect between the qualities people say they want and the spouses they choose happens because people don’t talk about money, relationship experts say. Couples never come around to addressing how their different attitudes toward spending would play out in day-to-day married life.

“You would be shocked at how many people don’t talk about these things before they get married,” said Susan Reach Winters, a divorce lawyer in Short Hills, New Jersey. “I mean, they’re willing to get naked with these people before they get married, but they don’t, or can’t, talk about money before they get married.”

But more broadly, just like the proverbial woman who says she wants a nice guy but really goes for the bad boys, people are also just plain bad at predicting what they want in love and marriage, the researchers found.

“We seem to have to have approximately no introspective accuracy as to what it is we want in a partner,” said Eli J. Finkel, a Northwestern psychology professor who is another co-author of the study.

Mr. Finkel speculated that the recession could amplify the fallout from monetary mismatchings.

“People may not think about these things when they first get married,” he said. “But a bad economy serves as a crucible for complementary marriages.”