Table 2. Fit indices for the reported models.

Model	N	χ2	df	RMSEA [90% CI]	SRMR
Intelligence
1.	1898	214.46	47	0.04 [0.04, 0.05]	0.03
2.	1898	822.31	199	0.04 [0.04, 0.04]	0.04
3.	1898	972.99	271	0.04 [0.03, 0.04]	0.04
Personality
1.	1872	3416.21	257	0.08 [0.08, 0.08]	0.08
2.	1886	7388.16	999	0.06 [0.06, 0.06]	0.06
3.	1898	8505.10	1222	0.06 [0.06, 0.06]	0.06

Note. All reported χ² were significant (p<.001).

df = Degrees of freedom.

RMSEA = Root mean squared error of approximation.

SRMR = Standardized root mean residual.

CI = Confidence interval.

Model 1: Paternal age, twin’s age at testing, sex, zygosity.

Model 2: As model 1, plus mother’s trait level, father’s trait level.

Model 3: As model 2, plus number of older siblings/birth order, birth weight, birth complications.