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Heredity and environment are powerful influences on development. Not only do they interact, but environmental factors often support hereditary traits (Plomin et al., 2016; Scarr & McCartney, 1983). Gene–environment correlation refers to the finding that many genetically influenced traits tend to be associated with environmental factors that promote their development (Lynch, 2016). That is, genetic traits influence children’s behavior, which is often supported or encouraged by the environment (Knafo & Jaffee, 2013). There are three types of gene–environment correlations—passive, evocative, and active.

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Figure 2.8 Gene–Environment Correlation

Parents create homes that reflect their own genotypes. Because parents are genetically similar to their children, the homes that parents create support their own preferences but also correspond to their child’s genotype—an example of a passive gene–environment correlation (Wilkinson, Trzaskowski, Haworth, & Eley, 2013). It is a passive gene–environment correlation because it occurs regardless of the child’s behavior. For example, a parent might provide genes that predispose a child to develop music ability and create a home environment that reflects the parent’s interest and ability in music, which then also happens to support the child’s musical ability, as shown in the top photo in Figure 2.8. This type of gene–environment correlation tends to occur early in life because parents create rearing environments for their infants and young children.

Children naturally evoke responses from others and the environment, just as the environment and the actions of others evoke responses from the individual. In an evocative gene–environment correlation, a child’s genetic traits (e.g., personality characteristics, including openness to experience) influence the social and physical environment, which in turn shape development in ways that support the genetic trait (Burt, 2009; Klahr, Thomas, Hopwood, Klump, & Burt, 2013). For example, active, happy infants tend to receive more adult attention than do passive or moody infants (Deater-Deckard & O’Connor, 2000), and even among infant twins reared in the same family, the more outgoing and happy twin receives more positive attention than does the more subdued twin (Deater-Deckard, 2001). Why? Babies who are cheerful and smile often influence their social world by evoking smiles from others, which in turn supports the tendency to be cheerful. In this way, genotypes influence the physical and social environment to respond in ways that support the genotype. Children who engage in disruptive play tend to later experience problems with peers (Boivin et al., 2013). To return to the music example, a child with a genetic trait for music talent will evoke pleasurable responses (e.g., parental approval) when she plays music; this environmental support, in turn, encourages further development of the child’s musical trait. In addition, individuals vary in their sensitivity to environmental stimuli; some children may be more affected by environmental stimuli due to their genetic makeup (Belsky & Hartman, 2014; Pluess, 2015).

Children also take a hands-on role in shaping their development. Recall from Chapter 1 that a major theme in understanding human development is the finding that individuals are active in their development. Here we have an example of this theme. As children grow older, they have increasing freedom in choosing their own activities and environments. An active gene–environment correlation occurs when the child actively creates experiences and environments that correspond to and influence his genetic predisposition. For example, the child with a genetic trait for interest and ability in music actively seeks experiences and environments that support that trait, such as friends with similar interests and after-school music classes. This tendency to actively seek out experiences and environments compatible with and supportive of our genetic tendencies is called niche-picking (Corrigall & Schellenberg, 2015; Scarr & McCartney, 1983).

The strength of passive, evocative, and active gene–environment correlations changes with development, as shown in Figure 2.9 (Scarr, 1992). Passive gene–environment correlations are common at birth, as caregivers determine infants’ experiences. Correlations between their genotype and environment tend to occur because their environments are made by genetically similar parents. Evocative gene–environment correlations also occur from birth, as infants’ inborn traits and tendencies influence others, evoking responses that support their own genetic predispositions. In contrast, active gene–environment correlations take place as children grow older and more independent. As they become increasingly capable of controlling parts of their environment, they engage in niche-picking by choosing their own interests and activities, actively shaping their own development. Niche-picking contributes to the differences we see in siblings, including fraternal twins, as they grow older. But identical twins tend to become more similar over time perhaps because they are increasingly able to select the environments that best fit their genetic propensities. As they age, identical twins—even those reared apart—become alike in attitudes, personality, cognitive ability, strength, mental health, and preferences, as well as select similar spouses and best friends (McGue & Christensen, 2013; Plomin & Deary, 2015; Plomin et al., 2016; Rushton & Bons, 2005).

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Figure 2.9 Development Stage and Gene–Environment Correlations