Scientists believe that many people are born winners with a rock solid self-confidence as much to do with nature as it is with nurture.

The new belief that this is something people are born with conflicts with previous theories that confidence is based on upbringing and other environmental factors.

Psychiatrists now say that the ability to perform under pressure may be something some people are born with.

They have also shown that children with a greater belief in their own abilities often perform better at school, even if they are actually less intelligent.

Professor Robert Plomin, of the Institute of Psychiatry, King's College, London, said: "Everyone has assumed self confidence is a matter of environment."

"Our research shows that it is certainly genetically influenced and that self confidence predicts achievement at school."

Prof Plomin and his colleague, Corina Greven, carried out research which showed that children's self-perceptions of their abilities have a clear genetic basis.

A team led by Prof Plomin and Ms Greven, also of King's College, asked over 3,700 twin pairs to rate their abilities in a number of core school subjects.

By studying both identical and non-identical twins, from the age of seven to ten, they were able to assess the relative contributions of genes and environment.

Twins studies are useful because identical twins have the same genes and the same environment whereas non-identical have different genes but the same environment.

Therefore by comparing the two, many "nature versus nurture" questions can be answered.

Contrary to accepted wisdom, they found that confidence is heavily influenced by genetics, at least as much as IQ is.

These genes would appear to influence school performance independent of IQ genes, with shared environment having only a negligible influence.

Indeed, it was easier to predict the children's school results by youngsters' perception of their own abilities than by an objective assessment of their academic talents.

Prof Plomin added: "We are not saying that genes are the only factor or that upbringing and environment cannot change things.

"But there is something genetic in self confidence which I would think of as a personality trait that would be stable throughout life."

The study's findings are published in the June issue of the journal Psychological Science.