Table II:

Phenotypic and Cross-Twin Correlations for Semantic Fluency Measures

		Phenotypic Correlations with:				Cross-Twin Cross-Trait Correlations
Variable	N	Age	Education	Sex		MZ All	DZ All	MZ Male	DZ Male	MZ Female	DZ Female	DZ Opp Sex
Full Sample	21684	−0.38	0.28	0.01		0.57	0.36	0.55	0.38	0.60	0.40	0.28
By Country
Australia	588	−0.32	0.15	0.08		0.53	0.24	0.39	0.31	0.62	0.15	0.28
Denmark	18511	−0.43	0.34	−0.02		0.54	0.32	0.50	0.34	0.57	0.38	0.23
USA	2585	−0.23	0.22	−0.23		0.40	0.23	0.41	0.18	0.40	0.19	0.34
By Study
OATS	588	−0.32	0.15	0.08		0.53	0.24	0.39	0.31	0.62	0.15	0.28
LSADT	4232	−0.33	0.27	−0.16		0.44	0.30	0.42	0.36	0.45	0.24	0.37
MADT	4261	−0.12	0.27	−0.07		0.40	0.27	0.42	0.30	0.40	0.19	0.34
MIDT	10018	−0.28	0.27	0.12		0.56	0.29	0.56	0.30	0.56	0.37	0.24
MIDUS	1105	−0.29	0.32	−0.11		0.40	0.27	0.42	0.30	0.40	0.19	0.34
VETSA	1480	−0.13	0.13	-		0.41	0.17	0.41	0.17	-	-	-

Note: Columns 3–5 display phenotypic correlations between semantic fluency and the other primary study variables: age, education, and sex. Columns 6–11 display the cross-twin correlations for verbal fluency among monozygotic (MZ) and dizygotic (DZ) twin pairs. Cross-twin correlations do not adjust for age, education, and sex effects. Significant correlations are displayed in bold (p < .05). Australian Studies: OATS = Older Australian Twins Study; Danish Studies: LSADT = Longitudinal Study of Aging Danish Twins, MIDT/MADT = Middle Age Danish Twin Studies; USA Studies: MIDUS = Midlife in the United States, VETSA = Vietnam Era Twin Study of Aging.