Men concerned about their performance in bed or women uncertain about the solidity of a relationship are more likely to cheat on their partners, according to a study published in the journal Archives of Sexual Behaviour.

The study found that the personality, sexual predilections and interpersonal factors were more likely to predict fidelity than demographic factors such as religion, marital status, education or gender. Researchers assembled about 900 men and women who had been in relationships lasting anywhere from three months to 43 years and tried to isolate demographic variables from the quality of their relationships or their personalities in bed.

Men and women cheated at about the same rate, but for different reasons. Men were more likely to cheat if they were easily aroused or if they had performance anxiety -- that is, if they were fearful of not delivering between the sheets. In the latter situation, men sought out new partners because they fear judgment. That parallels another study finding that people who were uncomfortable with intimacy were less likely to be faithful.

"People might seek out high-risk situations to help them become aroused, or they might choose to have sex with a partner outside of their regular relationship because they feel they have an 'out' if the encounter doesn't go well - they don't have to see them again," said Robin Milhausen of the University of Guelph.

For women, it is all about the relationship. Women who feel unfulfilled or unhappy in their relationship were far more likely to find new lovers. Milhausen acknowledged that the findings seem to re-enforce sexual stereotypes -- men being concerned with sexual gratification while women seek emotional validation, but he noted that "the caveat is that there are a lot of variants and factors that are not explained here that might impact whether someone cheats."