By Helen Briggs BBC News Online science reporter

Research suggests they are genetically programmed to be adept in social situations.

Having two X chromosomes may be protective against whatever predisposes someone to not being able to make sense of the social world

Dr Ruth Campbell, University College London

The key is the female X chromosome, which seems to protect against disorders linked with poor social interactions.

Dr Ruth Campbell of University College London, UK, says there may be genes on the X chromosome that are important for the development of social skills.

Bringing up baby

Men have only a single X chromosome. It is possible that the difficulties some experience in displaying appropriate social behaviour could be down to this, she says.

"Having two X chromosomes may be protective against whatever predisposes someone to not being able to make sense of the social world," she told BBC News Online.

"It makes sense for women, who have to give birth, to have evolved so that the development of their social aptitude is well protected from accidents of inheritance or environment.

"Their survival, and that of their babies, is particularly dependent on reading social situations accurately."

Gaze perception

The evidence comes from a study of women with Turner's Syndrome, a female genetic condition caused by a missing or defective X-chromosome.

Our chromosomes

These are the structures into which our cells bundle the DNA, the "code of life" We all have 22 autosomes and 2 sex chromosomes In females, the sex chromosomes are the 2 X chromosomes Males have one X chromosome and one Y chromosome

Many women with Turner's Syndrome have difficulties in social interactions, and find it hard to read body language. They have normal intelligence, however, and good verbal abilities.

A team at the department of human communication science tested the accuracy of gaze perception in 41 women with Turner's Syndrome.

The women were shown pictures of two faces, one looking directly forward and the other with a slightly averted gaze.

The researchers found that women with Turner's Syndrome were much worse at distinguishing precisely where someone was looking - and this affected their ability to tell if they were being looked at directly.

Autism conditions

Dr Campbell says it is not that men are worse than women at social cognition but among people who are really bad at it you are far more likely to find men than women.

Autism and autism-like conditions such as Asperger's syndrome are far more prevalent in men than women but it is not clear why.

David Potter of the National Autistic Society says a possible link with the X chromosome is a plausible theory but far more research needs to be done.

"It's another small piece of the jigsaw but it's not going to explain all cases of autism," he said.

The research is published in the online edition of the Royal Society's Proceedings A and B.