Table 4.

Intraclass correlation estimates (Est), standard errors (SEs), and lower and upper 95% confidence limits (LCL, UCL) by phenotype, zygosity, age, and affectedness (Aff) criteria.

Outcome	Aff criterion	Age	MZ twins				DZ twins
			Est	SE	LCL	UCL	Est	SE	LCL	UCL
PPVT-III Vocabulary	−1.00 SD	4	.72	.08	.51	.84	.39	.09	.16	.54
		6	.75	.10	.50	.90	.32	.16	.00	.58
	−1.25 SD	4	.59	.12	.28	.79	.51	.10	.26	.67
		6	.76	.11	.46	.95	.57	.15	.20	.81
	−1.50 SD	4	.47	.18	.01	.76	.54	.12	.22	.74
		6	.85	.10	.58	1.00	.66	.18	.21	.95
TOLD-P:3 Spoken Language	−1.00 SD	4	.73	.07	.55	.84	.55	.07	.38	.65
		6	.79	.06	.63	.89	.46	.07	.27	.58
	−1.25 SD	4	.63	.09	.40	.78	.52	.08	.32	.65
		6	.87	.05	.75	.95	.46	.08	.24	.60
	−1.50 SD	4	.72	.11	.43	.91	.42	.13	.10	.63
		6	.84	.06	.68	.94	.47	.10	.21	.64
TOLD-P:3 Semantics	−1.00 SD	4	.55	.09	.31	.70	.41	.08	.22	.54
		6	.61	.09	.38	.77	.35	.08	.14	.49
	−1.25 SD	4	.41	.13	.07	.63	.26	.11	.00	.44
		6	.72	.08	.51	.86	.33	.10	.08	.50
	−1.50 SD	4	.47	.17	.04	.74	.34	.12	.02	.54
		6	.77	.08	.56	.90	.34	.11	.05	.52
TOLD-P:3 Syntax	−1.00 SD	4	.80	.06	.65	.89	.46	.07	.27	.58
		6	.80	.06	.65	.90	.48	.07	.30	.61
	−1.25 SD	4	.61	.10	.36	.78	.45	.09	.22	.60
		6	.83	.06	.68	.92	.39	.09	.15	.54
	−1.50 SD	4	.57	.12	.26	.77	.46	.11	.18	.64
		6	.88	.05	.76	.96	.44	.10	.18	.60
GFTA-2 Speech	−1.00 SD	4	.84	.09	.61	.98	.72	.11	.44	.90
		6	.84	.09	.62	.99	.08	.23	.00	.46
	−1.25 SD	4	.93	.06	.78	1.00	.79	.10	.53	.96
		6	.92	.07	.74	1.00	.47	.25	.00	.88
	−1.50 SD	4	.91	.08	.70	1.00	.84	.10	.58	1.00
		6	.91	.08	.70	1.00	.56	.24	.00	.96
MLU	−1.00 SD	4	.64	.09	.40	.79	.22	.10	.00	.38
		6	.62	.10	.35	.79	.25	.10	.00	.41
	−1.25 SD	4	.66	.10	.40	.83	.34	.10	.08	.51
		6	.36	.15	.00	.61	.17	.13	.00	.38
	−1.50 SD	4	.83	.08	.63	.95	.28	.13	.00	.49
		6	.67	.13	.33	.88	−.07	.21	.00	.28
TEGI Composite	−1.00 SD	4	.82	.05	.69	.91	.58	.06	.43	.68
		6	.78	.06	.63	.88	.43	.08	.23	.56
	−1.25 SD	4	.81	.06	.66	.90	.60	.06	.44	.70
		6	.88	.04	.77	.95	.43	.08	.21	.56
	−1.50 SD	4	.83	.06	.69	.92	.61	.06	.45	.72
		6	.90	.04	.79	.96	.47	.09	.25	.61
TEGI Screener	−1.00 SD	4	.85	.05	.73	.93	.58	.06	.42	.69
		6	.65	.09	.42	.79	.50	.08	.29	.64
	−1.25 SD	4	.86	.05	.74	.94	.61	.06	.45	.71
		6	.75	.08	.56	.88	.51	.09	.28	.65
	−1.50 SD	4	.89	.04	.78	.96	.64	.06	.47	.74
		6	.80	.07	.62	.91	.54	.09	.30	.69
CMMS Nonverbal IQ	−1.00 SD	4	.32	.16	.00	.58	.32	.11	.03	.50
		6	.81	.10	.56	.98	.12	.24	.00	.51
	−1.25 SD	4	.08	.27	.00	.52	.48	.13	.14	.70
		6	.43	.09	.20	.57	.24	.10	.00	.40
	−1.50 SD	4	.53	.27	.00	.98	.44	.25	.00	.85
		6	.61	.06	.44	.72	.51	.06	.36	.61

Note. MZ = monozygotic; DZ = dizygotic; PPVT-III = Peabody Picture Vocabulary Test–III; TOLD-P:3= Test of Language Development–Primary: Third Edition; GFTA-2 = Goldman-Fristoe Test of Articulation–Second Edition; MLU = mean length of utterance as calculated by SALT software; TEGI = Rice–Wexler Test of Early Grammatical Impairment; CMMS = Columbia Mental Maturity Scale.