Figure 2.

Potential contributions to a polygenic score association. First, direct genetic effects are ones that transpire largely through inside-the-skin processes that are best described in terms of the actions of molecules and cells within the body. A physical characteristic like hair texture is an example of a phenotype where inside-the-skin processes predominate. Second, transactional genetic effects originate from a person’s own genome but require interaction with the environment, thereby transpiring through processes both inside and outside the skin. Most traits of interest to developmental psychologists, such as mental health, physical health, personality, cognitive skills, and academic achievement, will depend on transactional gene–environment effects. Third, caregivers’ genes, even those that are not transmitted during reproduction, can affect child outcomes through correlated environmental processes; this process is referred to as genetic nurture or indirect genetic effects. Fourth, associations of polygenic scores with developmental outcomes may derive from confounding due to unaccounted population stratification and nonrandom mating.