Model fitting results for additive genetic (A), shared environmental (C) and residual (E; i.e., non-shared environment and error) components of variance, with 95% confidence intervals.

Numbers of pairs are shown for male (m), female (f) and opposite sex (os) monozygotic (MZ) and dizygotic (DZ) twins; figures include incomplete pairs (i.e., those with missing data for one twin). All variables except for mathematics are composites.