Figure 1.

Genetic and environmental influences on AB appear remarkably similar in their magnitude despite different operationalization methods, assessment methods, age of assessment, zygosity assessment methods, gender of the participants or whether twin versus adoption design was used. This figure represents a selection of the statistics reported in Rhee & Waldman (2002) meta-analysis. A, additive genetic influences; D, dominant genetic influences; C, shared environmental influences; E, non-shared environmental influences.