There is virtually no psychological difference between the sexes, and suggestions in books such as Men are from Mars, Women from Venus are nonsense, experts say.

Psychologists claim they have debunked the idea that the sexes think in completely different ways in a study that found qualities such as empathy are not the sole pre-serve of one gender.

Although there are small average differences between men and women for some qualities, such as aggression, there is so much overlap that no trait can be designated as either male or female, they found.

The findings explain why gay and lesbian couples have the same sort of arguments as heterosexuals, demonstrating that it is not gender but individual characteristics that cause friction in relationships, the psychologists said.

Writing in the Journal of Personality and Social Psychology, they claimed: "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 psychologists reanalyzed data from 13 studies which claimed to show significant psychological differences.

The research covered 13,300 people and contained information on 122 characteristics including intimacy and sexuality, as well as the so-called "big five" traits which are said to define our personality: extroversion, openness, agreeableness, emotional stability and conscientiousness.

The psychologists found that while certain stereotypical activities, such as boxing or using cosmetics, were more common among one gender, no such divide existed for most personality traits. Many of the men were found to be empathetic, a quality traditionally seen as "female," while women were often good at math, a so-called "male" skill.

There were overall differences between the sexes on average, but in virtually all categories there was a great deal of variability within each sex and overlap, the psychologists found.

Prof. Harry Reis of New York state's University of Rochester, a co-author of the study, said: "People think about the sexes as distinct categories. 'Boy or girl?' is the first question parents are asked about their newborn, and sex persists through life as the most pervasive characteristic used to distinguish categories among humans.

"What we found is that overwhelmingly men and women were not categorically different people."