Mechanisms of gene-by-environment interaction and gene-environment correlation may be consistent with our results. In early childhood, it may be the case that substantial and extensive gene-by-environment interaction takes place based on the shared environment provided by parents. This process would explain the very large heritability of personality in early childhood. As children mature and begin to leave the shared environment, heritability begins to decrease indicating that the gene-by-environment interactions may not be particularly lasting (i.e., a scarring effect that would persist beyond the environmental exposure), but rather frequently recur over early development. However, one would expect that this process would entail a decrease in genetic stability, as children move away from shared environments to which they differentially respond. We found the opposite trend, a fairly constant increase in genetic stability through childhood. Gene-environment correlation may explain the increase in genetic stability. Children increasingly gain the autonomy to select environments consistent with their genotype with age (Scarr & McCartney, 1983). Age-dependent gene expression is another possible explanation for relatively low genetic stability in childhood with increases into adulthood. As children mature,
