Abstract
Both the environment and genetics are likely to influence the development of cognitive talent during the preschool years. It is not known to what degree or how these influences differ from those throughout the range of ability. 1943 twin pairs were assessed at 2, 3 and 4 years of age using diverse verbal and nonverbal cognitive measures. Consistently high scoring children were selected on a general cognitive factor. From behavioural genetic model fitting analyses, substantial shared environmental (70%) and modest genetic influences (20%) were found in the high group and this matched the aetiology of the entire sample. Strong genetic predisposition was not apparent. Individual differences in cognitive ability and high ability is largely due to shared environment during the preschool years.