Table 1.

Descriptive Statistics for All Measures in the Study

Measure	N	M	SD	Range	Skewness Kurtosis		rMZ	rDZ
Executive Function Tasks
Stroop	1180	32.86	7.08	−3.40, 5.42	0.00	2.39	0.31	0.14
AX-CPT	1059	1.09	0.26	−4.54, 1.42	−1.42	2.88	0.43	0.35
Letter-Number	1202	9.28	2.25	−3.35, 3.23	0.10	0.47	0.36	0.21
Reading Span	1197	33.99	4.76	−3.35, 2.04	−0.38	0.06	0.56	0.36
Digit Span	1058	15.83	3.69	−2.54, 3.25	0.36	−0.06	0.57	0.39
Trail Making Test	1047	85.64	28.56	−4.09, 2.33	−1.71	4.97	0.22	0.12
Category Switching	1202	11.00	2.93	−4.05, 2.78	−0.53	0.98	0.18	0.11
Anxiety and Depression Symptoms
STAI - Trait	1196	3.41	0.29	3.00, 4.33	0.50	−0.52	0.42	0.19
CESD	1195	1.69	0.99	0, 3.99	−0.17	−0.72	0.32	0.22
Additional Measures
STAI - State	1200	3.40	0.28	3.00, 4.22	0.31	−0.75	0.30	0.17
AFQT	1203	0.34	0.67	−2.05, 2.32	0.01	−0.31	0.70	0.38

Note: Descriptive statistics for all dependent measures are shown before adjusting for age (for all measures), but after transformation (for measures of anxiety and depression). The final two columns display the cross-twin correlations for monozygotic (r_MZ) and dizygotic twins (r_DZ). Significant cross-twin correlations are displayed in bold (p < .05) AX-CPT = AX – Continuous Performance Test, STAI = State-Trait Anxiety Inventory, CESD = Center for Epidemiologic Studies – Depression scale, AFQT = Armed Forces Qualification Test percentile score (transformed).