For generations, popular writers think that men and women are so psychologically dissimilar they could hail from entirely different planets.
But a new study shows that it's time for the Mars/Venus theories about the sexes to come back to Earth.
From empathy and sexuality to science inclination and extroversion, statistical analysis of 122 different characteristics involving 13,301 individuals shows that men and women, by and large, do not fall into different groups.
In other words, no matter how strange and inscrutable your partner may seem, their gender is probably only a small part of the problem.
"People think about the sexes as distinct categories," says Harry Reis, professor of psychology at the University of Rochester and a co-author on the study.
But the handy dichotomy often falls apart under statistical scrutiny. For example, it is not at all unusual for men to be empathic and women to be good at math - characteristics that some research has associated with the other sex, said lead author Bobbi Carothers, who completed the study as part of her doctoral dissertation at Rochester.
"Sex is not nearly as confining a category as stereotypes and even some academic studies would have us believe," she adds.
The authors reached that conclusion by reanalyzing data from 13 studies that had shown significant, and often large, sex differences. Reis and Carothers also collected their own data on a range of psychological indicators.
They revisited surveys on relationship interdependence, intimacy, and sexuality. They reopened studies of the "big five" personality traits: extroversion, openness, agreeableness, emotional stability, and conscientiousness.
Statistically, men and women definitely fall into distinct groups, or taxons, based on anthropometric measurements such as height, shoulder breadth, arm circumference, and waist-to-hip ratio. And gender can be a reliable predictor for interest in very stereotypic activities, such as scrapbooking and cosmetics (women) and boxing and watching pornography (men).
But for the vast majority of psychological traits, including the fear of success, mate selection criteria, and empathy, men and women are definitely from the same planet.
Instead of scores clustering at either end of the spectrum-the way they do with, say, height or physical strength-psychological indicators fall along a linear gradation for both genders. With very few exceptions, variability within each sex and overlap between the sexes is so extensive that the authors conclude it would be inaccurate to use personality types, attitudes, and psychological indicators as a vehicle for sorting men and women.
"Thus, contrary to the assertions of pop psychology titles like Men Are From Mars, Women Are From Venus, it is untrue that men and women think about their relationships in qualitatively different ways," the researchers wrote.
That men and women approach their social world similarly does not imply that there are no differences in average scores between the sexes. Average differences do exist, wrote the authors.
"The traditional and easiest way to think of gender differences is in terms of a mean difference," Carothers and Reis said.
But such differences "are not consistent or big enough to accurately diagnose group membership" and should not be misconstrued as evidence for consistent and inflexible gender categories, they concluded.
"Those who score in a stereotypic way on one measure do not necessarily do so on another," the researchers noted.
The best evidence we have that the so-called Mars/Venus gender division is not the true source of friction within relationships, said Reis, is that "gay and lesbian couples have much the same problems relating to each other that heterosexual couples do. Clearly, it's not so much sex, but human character that causes difficulties."
The study will be published in the February issue of the Journal of Personality and Social Psychology.