IQ of 5- and 7-year old Dutch twins was measured in order to study changes in the genetic architecture of cognitive functioning. The continuity and dynamics in genetic and environmental influences were examined by means of development model of data processing. The results show that genetic influences persist during this age interval and greatly gain in relative importance. Shared family background influences IQ in early childhood but their relative importance becomes smaller. Unique environment manifests itself age-specifically and accounts for about a quarter of total variance of IQ in both 5- and 7-year old twins.