No group of men and women in history has ever been less different, or less at the mercy of their biology, than those living today’s societies. And yet 21st-century men and women are drawn to a mythology that says that differences between men and women are profound and unalterable. So what is it that attracts us to the concept of Mars versus Venus?

The idea that men and women metaphorically "speak different languages" - that they use language in different ways and for different reasons - is one of the great myths of our time.

Research debunks the various smaller myths that contribute to it: for instance, that women talk more than men (research suggests the opposite); that women's talk is cooperative and men's competitive (research shows that both sexes engage in both kinds of talk); that men and women systematically misunderstand one another (research has produced no good evidence that they do).

There is a great deal of similarity between men and women, and the differences within each gender group are typically as great as or greater than the difference between the two. Many differences are context-dependent: patterns that are clear in one context may be muted, nonexistent or reversed in another, suggesting that they are not direct reflections of invariant sex-specific traits.

If these points were acknowledged, the science soundbites would be headed "Men and women pretty similar, research finds", and popular psychology books would bear titles like There's No Great Mystery About the Opposite Sex or We Understand Each Other Well Enough Most of the Time. Of course, these titles do not have the makings of bestsellers, whereas the "men and women are from different planets" story is a tried and tested formula. What does the myth of Mars and Venus do for us, that we return to it again and again?

Being normal

For the past 15 years, the myth of Mars and Venus has told us what is normal for men and women in the sphere of language and communication. Its generalisations about male and female language use have come to influence our expectations and our judgments of how men and women communicate.

We see its less benign consequences when employers view women as better candidates than men for jobs that demand the ability to chat (and men as better candidates than women for jobs that demand verbal authority and directness). We see them when parents and educators expect girls to be better at languages, and boys to be better at maths.

We see them when jurors at rape trials give men who claim to have "misread a woman's signals" the benefit of the doubt. And we see them in a small way every time someone makes a joke about how much women talk or how useless men are at expressing their feelings.

Being different

Sex differences fascinate us to a degree that most biological differences don't. It is conceivable, for instance, that you could diagnose a writer's age from a sample of prose. And to my knowledge, there has never been a bestselling popular science book about the differences between right- and left-handed people.

Is that what the myth of Mars and Venus is about? A recurring theme in Mars and Venus literature is men's allegedly underdeveloped capacity for empathy and caring.

This testifies to what has not changed. What has happened in the past 40 years might be better described as an increasing masculinisation of society, in the sense that the major shift has involved middle-class women's aspirations and attitudes becoming more like men's, focused on individual achievement and individual freedom.

(Extract from Deborah Cameron’s new book ‘The myth of Mars and Venus’)