AP PSYCHOLOGY

Detailed explanation-1: -Twin studies have been described as “the perfect natural experiment to separate familial resemblance from genetic influence.” 16 Recent large twin studies of refractive error have found high heritabilities of 84% to 86%, 17 89% to 94%, 18 and 75% to 88%.

Detailed explanation-2: -Heritability can give initial clues as to the relative influences of “nature” (genetics) and “nurture” (environment) on complex traits, and it can give researchers a place to start teasing apart the factors that influence these traits.

Detailed explanation-3: -Heritability is expressed as H2 = Vg/Vp, where H is the heritability estimate, Vg the variation in genotype, and Vp the variation in phenotype. Heritability estimates range in value from 0 to 1.

Detailed explanation-4: -Three main sources of data are used for heritability studies; monozygotic (MZ) and dizygotic (DZ) twins, adoption studies, and family studies. For each data source, an example of a commonly used heritability formula is included to clarify the assumptions made about relationships between relatives.