Table 1.

Phenotypic Correlations Achievement and General Cognitive Ability

	Hyperactivity rating, r
Correlate	Parent	Same teacher	Different teacher
Unadjusted achievement^a
Males	−.33^**	−.42^**	−.39^**
Females	−.29^**	−.44^**	−.47^**
General cognitive ability
Males	−.16^**	−.19^**	−.17^**
Females	−.15^**	−.20^**	−.21^**
Achievement
Males	−.29^**	−.38^**	−.35^**
Females	−.24^**	−.38^**	−.41^**

Note. Parent ratings: N males = 1,572, N females = 1,804; same teacher ratings: N males = 1,104, N females = 1,290; different teacher ratings: N males = 632, N females = 646. To correct for the lack of independence arising from the fact that we have two members from a family, the significance levels for all correlations are based on the number of twin pairs rather than individuals.

Scores were not residualized for general cognitive ability.

^**

p<.01.