Children who are outgoing and adventurous as toddlers have substantially higher IQs by the time they are preteens.

Scientists at two Californian universities compared how eagerly youngsters sought out new experiences at age three and how well they performed on various tests of mental ability eight years later.

The most adventurous and curious three-year-olds scored 12 points higher on total IQ when they were tested as preteens.

The children also showed superior scholastic and reading ability.

This measurable difference in mental ability held true for boys and girls, and across variations in ethnic background and income levels. The amount of parental involvement and education did not appear to matter.

The study did not show whether the children`s outgoing curiosity as toddlers was the basis of higher IQ scores or whether children who have higher IQs are, by nature, more curious and outgoing - but the researchers believe the former to be the case.

They also said it may be possible to teach the helpful behaviour to other children.

"Young children who physically explore their environment, engage socially with other children, and verbally interact with adults, create for themselves an enriched, stimulating, varied and challenging environment.

"This results in enhanced cognitive ability and better school performance," the researchers said.