Table 3.

ACE Model Fit and Estimates of Genetic, Shared Environment, and Nonshared Environment Contributions to Fearful and Self-conscious Shyness

Measure	Model	-2LL	df	AIC	Δdf	Δχ2	p	h2	95%CIh2	c2	95%CIc2	e2	95%CIe2
6 observed fearful shyness	ACE	132.41	163	−7.59	-	-	-	.00	.00–.50	.33	.00–.51	.67	.48–.88
	AE			−0.48	1	1.52	0.22	.34	.11–.53	-	-	.66	.47–.89
	CE			−2.00	1	0.00	0.99	-	-	.33	.12–.51	.67	.49–.88
	E			5.24	2	9.24	<.01	-	-	-	-	1.00	1.00–1.00
12 observed fearful shyness	ACE	492.11	217	20.11	-	-	-	.00	.00–.47	.34	.00–.49	.66	.49–.84
	AE			0.43	1	2.43	0.12	.36	.14–.54	-	-	.64	.46–.86
	CE			−2.00	1	0.00	0.99	-	-	.34	.16–.49	.66	.51–.84
	E			8.39	2	12.39	<.01	-	-	-	-	1.00	1.00–1.00
12 months parent-reported fearful shyness	ACE	613.23	201	211.23	-	-	-	.69	.34–.80	.00	.00–.00	.31	.20–.47
	AE			−2.00	1	0.00	.99	.69	.53–.80	-	-	.31	.20–.47
	CE			8.94	1	10.94	<.01	-	-	.48	.32–.62	.52	.38–.68
	E			33.94	2	37.94	<.01	-	-	-	-	1.00	1.00–1.00
22 months parent-reported fearful shyness	ACE	749.07	281	187.07	-	-	-	.72	.46–.81	.00	.00–.22	.28	.19–.41
	AE			−2.00	1	0.00	0.99	.72	.59–.81	-	-	.28	.19–.41
	CE			15.29	1	17.29	<.01	-	-	.47	.34–.59	.53	.41–.66
	E			49.54	2	53.54	<.01	-	-	-	-	1.00	1.00–1.00
19–28 months intercept of self-conscious Shyness	ACE 3	−1176.9	423	−2022.93	-	-	-	.86	.60–.92	.03	.00–.29	.10	.08–.14
	AE			−1.96	1	0.05	.83	.90	.86–.92	-	-	.10	.08–.14
	CE			62.90	1	64.90	<.01	-	-	.69	.62–.76	.31	.24–.38
	E			200.27	2	204.27	<.01	-	-	-	-	1.00	1.00–1.00

Note−2LL = −2 times the log likelihood. df = degrees of freedom. AIC = Akaike’s Information Criterion. Δdf = change in degrees of freedom. Δχ² = change in chi-square value from the full model to reduced models. h² = additive genetic, c² = shared environmental, and e² = nonshared environmental standardized squared parameter estimates. ADE models were also fit for parent-reported fearful shyness, but nonadditive genetic influences (D) were nonsignificant. The best-fitting reduced model is in bold.