A new study says that a rock-solid self-confidence is in the genes and that upbringing has nothing to do with it.
The psychiatrists behind the study say that the ability to perform under pressure is more than a state of mind, and that some people are just born with it.
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.
"Everyone has assumed self confidence is a matter of environment," the Telegraph quoted Professor Robert Plomin, of the Institute of Psychiatry, King's College, London, as saying.
He added: "Our research shows that it is certainly genetically influenced and that self confidence predicts achievement at school."
Plomin and his colleague Corina Greven carried out the study, which showed that children's self-perceptions of their abilities are clearly based on genes.
The researchers asked over 3,700 both identical and non-identical twin pairs, from the age of seven to ten, to rate their abilities in a number of core school subjects and assessed the relative contributions of genes and environment.
Studying twins is useful because identical twins have the same genes and the same environment whereas non-identical have different genes but the same environment.
Thus, on comparing the two, many "nature versus nurture" questions can be answered.
Contrary to the age-old belief, the researchers found that confidence is heavily influenced by genetics, at least as much as IQ is.
The genes would appear to influence school performance independent of IQ genes, with shared environment having only a negligible influence.
"We are not saying that genes are the only factor or that upbringing and environment cannot change things," said Plomin.
He added: "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 have been published in the journal Psychological Science.