When it comes to sex, men are eternal optimists and romantic at heart

Men tend to have bigger sex drives than women and are more "sexually optimistic". When men were asked how many partners they expect to have over the next five years they averaged 3.4 compared to the female average of 1.9.

While women performed consistently better than men at psychological tests involving verbal fluency and locating objects, men tended to do better at "spatial awareness" tasks. Yet the gender differences are not completely distinct. Scientists found that about a fifth of men have typically "female" brains and an equal proportion of women have a mental approach typical of men.

Professor John Manning of the University of Central Lancashire said that the on-line survey was unprecedented because it involved people from about 170 countries and six ethnic groups. The survey was carried out for a television series called The Secrets of the Sexes, which begins on BBC1 tomorrow night.

Each person had to answer 200 questions about their sexual behaviour and attitudes and carry out a series of simple tests of personality traits and cognitive abilities, such as being able to match the correct angle of lines drawn on a screen.

"There are well established sex differences in abilities and behaviours but the question is where do they come from? Are they due to nurture, or nature or are they a mixture of both?" Professor Manning said.

The scientists found similar gender differences despite the country of origin or ethnic background of the participants.