Table 3.

Descriptive statistics for inhibitory control, impulsivity, novelty seeking, demographic, and overt and relational aggression composites.

Variable name	N	Mean	Standard deviation	Effect size ((male mean-female mean)/SDpooled)	t-test
Childhood inhibitory control (mother report CBQ)	834	4.8	1.0	−0.44	6.41*
Adolescent impulsivity (self-report EATQ)	708	0	0.59	0.25	−4.41*
Adolescent novelty seeking (self-report EATQ)	726	0	0.67	0.12	−1.91
Adolescent impulsivity (mother EATQ)	671	0	0.64	0.37	−6.35*
Adolescent novelty seeking (mother EATQ)	683	0	0.65	0.15	−3.71*
Avg. of puberty measures	746	3.0	1.0	−0.46	6.26*
Socioeconomic status composite	966	0	0.85	0.067	−1.13
Overt aggression (cotwin report)	975	0	0.78	0.46	−8.22*
Relational aggression (cotwin report)	976	0	0.72	0.20	−3.65*

Note: CBQ = Children's Behavior Questionnaire; completed when participants were approx. 7–8 years old; EATQ = Early Adolescent Temperament Questionnaire; completed when participants were approx. 12–13 years old; overt and relational aggression composites are from the MacArthur Health and Behavior Questionnaire; avg. of puberty measures is a composite of mother and self-reported physical development (breast development, body hair growth, etc.); socioeconomic status is an average of standardized values for family income and mother's number of years of education (reported by mothers); the measure of pubertal development ranges from 1 (has not begun) to 4 (is complete); impulsivity, novelty seeking, overt aggression, relational aggression, and SES composites are means of standardized items.

^*p < 0.05, 2-tailed (one level of significance used for all tests).