Heritability of Personality

Heritability is the degree to which variability in a characteristic can be explained by genetic variability in the population. The same concept applied to mental-health symptoms is discussed in 2-3 genetics; the broader nature-vs-nurture framing is in nature and nurture.

Identical twins have higher heritability factors compared to fraternal twins, suggesting some relationship between genetics and personality even in the same environment.

However, the heritability index overestimates the effect of genetics, since there could be other unmeasured environmental factors in twin studies (identical twins have no gender differences, are treated very similarly by others…)

Also, $h$ is not fixed, and depends on the sample. Homogenous environments result in a higher $h$ measurement.