Although behavioral genetic perspectives have historically emphasized what might be described as strong genetic determinism, current behavioral genetic thinking emphasizes dynamic and interactive processes by which genetic and environmental influences combine to influence behavioral development (Johnson, Penke, & Spinath, 2011; Krueger & Johnson, 2008). Gene-by-environment interaction occurs when heritable variation in a phenotype is differentially expressed in different environmental contexts (Johnson, 2007; Krueger, Johnson, & Kling, 2006). Gene-by-environment interaction can lead to age-related changes in heritability as a result of changing environmental contexts with age, such as entry into school, the workforce, or a long-term pair bond. Age-related changes in heritability can also result from biological changes associated with development, such as puberty. Gene-environment correlation refers to the nonrandom exposure of individuals to environmental experiences as functions of their genotypes (Plomin, DeFries, & Loehlin, 1977; Scarr & McCartney, 1983). In the case of passive gene-environment correlation, parental genotypes both influence the rearing experiences that parents provide to their offspring and are inherited by those offspring. In active and evocative gene-environment correlation, individuals select and evoke different environments on the basis of their genetically influenced preferences, motivations, and traits. These experiences may in turn affect psychological development.
