Scientists have found that the pleasure women get from making love is directly linked to the size of their partner’s bank balance.

They found that the wealthier a man is, the more frequently his partner has orgasms.

“Women’s orgasm frequency increases with the income of their partner,” said Dr Thomas Pollet, the Newcastle University psychologist behind the research.

He believes the phenomenon is an “evolutionary adaptation” that is hard-wired into women, driving them to select men on the basis of their perceived quality.

The study is certain to prove controversial, suggesting that women are inherently programmed to be gold-diggers.

However, it fits into a wider body of research known as evolutionary psychology which suggests that both men and women are genetically predisposed to ruthlessly exploit each other to achieve the best chances of survival for their genes.

The female orgasm is the focus of much research because it appears to have no reproductive purpose. Women can become pregnant whatever their pleasure levels.

Pollet, and Professor Daniel Nettle, his co-author, believed, however, that the female orgasm is an evolutionary adaptation that drives women to choose and retain high-quality partners.

He and Nettle tested that idea using data gathered in one of the world’s biggest lifestyle studies. The Chinese Health and Family Life Survey targeted 5,000 people across China for in-depth interviews about their personal lives, including questions about their sex lives, income and other factors. Among these were 1,534 women with male partners whose data was the basis for the study.

They found that 121 of these women always had orgasms during sex, while 408 more had them “often”. Another 762 “sometimes” orgasmed while 243 had them rarely or never. Such figures are similar to those for western countries.

There were of course, several factors involved in such differences but, said Pollet, money was one of the main ones.

He said: “Increasing partner income had a highly positive effect on women’s self-reported frequency of orgasm. More desirable mates cause women to experience more orgasms.”

This is not an effect limited to Chinese women. Previous research in Germany and America has looked at attributes such as body symmetry and attractiveness, finding that these are also linked with orgasm frequency. Money, however, seems even more important.

David Buss, professor of psychology at the University of Texas, Austin, who raised this question in his book The Evolution of Desire believes female orgasms have several possible purposes.

“They could promote emotional bonding with a high-quality male or they could serve as a signal that women are highly sexually satisfied, and hence unlikely to seek sex with other men,” he said. “What those orgasms are saying is ‘I'm extremely loyal, so you should invest in me and my children’."

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