Do you think you’re smarter than most? Chances are, your children will feel the same way about themselves.

A new study of thousands of twins suggests that intellectual confidence is genetically inherited, and independent from actual intelligence.

Moreover, these genetic differences predict grades in school, says Tomas Chamorro-Premuzic, a psychologist at Goldsmiths University in London, whose team found that 7- to 10-year-old children who achieved the best marks in school tended to rate their own abilities highly, even after accounting for differences due to intelligence and environment.

Nature or nurture?

Psychologists have long known that intelligence isn’t the only predictor of scholastic achievement and that intellectual confidence does a good a job of predicting grades as well.


“There has been a very, very big lobby within educational psychology against the notion of IQ,” says Chamorro-Premuzic. “And part of this lobby has been based on the idea that self-perceptions matter more than actual ability.”

Most of these researchers assumed that environmental factors – the influence of parents, teachers and friends – explained why some students think more of their abilities than others.

That’s only partially true, says Chamorro-Premuzic. About half of differences in children’s self-perceived abilities can be explained by environment. The other half seems to be genetic. For comparison, genes can explain about 80 per cent of the differences in height.

‘Challenges convention’

Chamorro-Premuzic’s team drew this conclusion by comparing intelligence, grades and personal ratings of 1966 pairs of identical twins and 1877 pairs of non-identical or fraternal twins. Identical twins share nearly all their genes, while fraternal twins just half. This allowed researchers to calculate how much of the differences in intellectual confidence were due to genetic versus environmental factors.

Determining what specific genes affect self-perceived ability won’t be easy, Chamorro-Premuzic says. Many of them should be linked to actual intelligence, but some will not. Genes that are linked to personality, which is another partially heritable trait, could also explain why some children think more highly of themselves than others.

“The findings challenge conventional thinking on student psychology and may suggest that the assumptions underlying student academic attainment are erroneous,” comments Timothy Judge, a psychologist at the University of Florida in Gainesville.

Journal reference: Psychological Science (DOI: 10.1111/j.1467-9280.2009.02366.x)