Evidence for genetic influence on both cross-situation and situation-specific components of behavior.

An assumption often made in the study of personality and in social psychology is that methods variance and situation-specific effects, as key components of measured behavioral variance, are environmental effects. The results of the present research refute that assumption. Nine measures-3 aspects of temperament measured in each of 3 ways-were obtained at age 24 months for twin sibships participating in the Louisville Twin Study. This report describes a new model that captures the unique information potentially available in such data, by combining multitrait-multimethod and twin-family analytic designs. The results indicated significant genetic influence on methods-situations components of variance along with genetic influence on traits. The findings support heuristics that include both situation-specific patterns of behavior and cross-situational consistencies.