The effects of gene-by-environment interaction may have implications for personality development and provide insights into the types of lifespan trends to expect for behavioral genetic estimates. Early in the lifespan, children may differentially respond to the common environment provided by their caregivers on the basis of genotypes. This type of gene-by-shared environment interaction results in environmental effects becoming coupled with genetic variation. Genetically similar individuals respond to the environment similarly and become more psychologically similar than individuals that share fewer genes. In other words, the effects of gene-by-shared environment interaction contribute to the estimate of genetic influence when not explicitly modeled (Purcell, 2002). Under such circumstances, genetic stability will be high when the same sorts of environments either recur over development or have a lasting impact. Moreover, if such effects compound over time, heritability would be expected to increase with age. However, it may also be the case that early gene-by-shared environment interactions for personality development are fleeting and give way to less genetically dependent environmental influence (e.g., Conley, 1984; Wolf & Weissing, 2012). If the effects of gene-by-shared environment
