Table 3.

Probandwise concordance and heritability estimates with LI identified by test scores or by SLP contact

	Concordant probands	Total n probands	Probandwise concordance	Concordant probands	Total n probands	Probandwise concordance	a2	95% Confidence interval
Definition of LI	MZ			DZ			a2	95% Confidence interval
SLI on language tests	38	97	39%	24	79	30%	0.00	0–0.45
NLI on language tests	92	146	63%	40	95	42%	0.36	0–0.79
With SLP contact	94	108	87%	36	91	40%	0.96	0.70–0.99
With SLP contact, normal nonverbal	44	50	88%	16	46	35%	0.97	0.56–0.99