Table 6.
Heritability, common environment, and residual error estimates (Est), standard errors (SEs), and lower and upper 95% confidence limits (LCL, UCL) by phenotype, zygosity, and age for the specific language impairment (SLI) and nonspecific language impairment (NLI) groups at −1.00 SD affectedness.
| Outcome | Group | Age |
h
2 heritability |
c
2 common environment |
e
2 residual error |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Est | SE | LCI | UCI | Est | SE | LCI | UCI | Est | SE | LCI | UCI | ||||
| PPVT-III Vocabulary | SLI | 4 | .35 | .32 | .00 | .87 | .14 | .25 | .00 | .55 | .51 | .12 | .21 | .71 | |
| 6 | .64 | .44 | .00 | 1.00 | .00 | .37 | .00 | .57 | .44 | .14 | .04 | .63 | |||
| NLI | 4 | ||||||||||||||
| 6 | |||||||||||||||
| TOLD-P:3 Spoken Language | SLI | 4 | .34 | .26 | .00 | .76 | .18 | .19 | .00 | .50 | .48 | .10 | .23 | .64 | |
| 6 | .45 | .22 | .00 | .81 | .24 | .17 | .00 | .52 | .32 | .08 | .11 | .45 | |||
| NLI | 4 | −.50 | .62 | .00 | .52 | .55 | .39 | .00 | 1.00 | .95 | .28 | .24 | 1.00 | ||
| 6 | .74 | .57 | .00 | 1.00 | .03 | .52 | .00 | .88 | .23 | .13 | .00 | .44 | |||
| TOLD-P:3 Semantics | SLI | 4 | .44 | .28 | .00 | .91 | .00 | .21 | .00 | .34 | .58 | .11 | .29 | .75 | |
| 6 | .60 | .27 | .00 | 1.00 | .00 | .21 | .00 | .31 | .46 | .10 | .16 | .60 | |||
| NLI | 4 | −.42 | .63 | .00 | .62 | .56 | .41 | .00 | 1.00 | .86 | .28 | .14 | 1.00 | ||
| 6 | .86 | .53 | .00 | 1.00 | .03 | .51 | .00 | .86 | .12 | .09 | .00 | .26 | |||
| TOLD-P:3 Syntax | SLI | 4 | .45 | .24 | .00 | .84 | .17 | .19 | .00 | .48 | .38 | .09 | .15 | .52 | |
| 6 | .55 | .22 | .00 | .90 | .17 | .17 | .00 | .46 | .28 | .08 | .09 | .40 | |||
| NLI | 4 | .27 | .47 | .00 | 1.00 | .24 | .34 | .00 | .79 | .49 | .19 | .00 | .80 | ||
| 6 | .85 | .56 | .00 | 1.00 | .00 | .52 | .00 | .81 | .24 | .12 | .00 | .39 | |||
| GFTA-2 Speech | SLI | 4 | .00 | .36 | .00 | .60 | .72 | .27 | .02 | 1.00 | .28 | .14 | .00 | .50 | |
| 6 | 1.22 | .32 | .39 | 1.00 | .00 | .30 | .00 | .14 | .48 | .07 | .00 | .24 | |||
| NLI | 4 | ||||||||||||||
| 6 | |||||||||||||||
| MLU | SLI | 4 | .91 | .34 | .03 | 1.00 | .00 | .26 | .00 | −.02 | .98 | .13 | .21 | .75 | |
| 6 | .74 | .32 | .00 | 1.00 | .00 | .24 | .00 | .22 | .62 | .12 | .14 | .63 | |||
| NLI | 4 | −.75 | .65 | .00 | .32 | .89 | .44 | .00 | 1.00 | .87 | .28 | .16 | 1.00 | ||
| 6 | |||||||||||||||
| TEGI Composite | SLI | 4 | .33 | .21 | .00 | .66 | .37 | .16 | .00 | .62 | .31 | .08 | .11 | .43 | |
| 6 | .71 | .21 | .17 | 1.00 | .07 | .18 | .00 | .36 | .23 | .06 | .06 | .33 | |||
| NLI | 4 | −.06 | .50 | .00 | .75 | .45 | .35 | .00 | 1.00 | .62 | .20 | .10 | .95 | ||
| 6 | |||||||||||||||
| TEGI Screener | SLI | 4 | .26 | .22 | .00 | .63 | .38 | .17 | .00 | .66 | .36 | .09 | .15 | .50 | |
| 6 | .26 | .27 | .00 | .70 | .32 | .20 | .00 | .66 | .42 | .10 | .17 | .58 | |||
| NLI | 4 | .18 | .45 | .00 | .92 | .34 | .34 | .00 | .89 | .48 | .17 | .04 | .77 | ||
| 6 | |||||||||||||||
Note. Negative heritability estimates occurred when the intraclass correlation for dizygotic twins was greater than the intraclass correlation for monozygotic twins, and heritability estimates greater than 1 occurred in models where the intraclass correlation for monozygotic twins was .5 greater than the intraclass correlation for dizygotic twins. LCLs and UCLs were truncated at 0 and 1, respectively; c 2 estimates of ≤ 0 were converted to 0. Heritability estimates are not reported for combinations in which one of the four cells in the Twin × Affectedness combination was empty within zygosity (for which the associated tetrachoric correlation is not reliable due to small Ns within a group). 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.