Table 1. Comparison of recovered group with matched comparison group on demographic and early language measures.
| Measure | Recovered ELD |
Matched, not ELD |
ELD, not recovered |
||||||
|---|---|---|---|---|---|---|---|---|---|
| M (SD) | n | M (SD) | n | t | P | d | M (SD) | n | |
| Initial definition of groups, using all recovered twins | |||||||||
| Vocabulary at 2 | 10.3 (3.6) | 373 | 49.1 (20.7) | 373 | — a | 3.2 | 8.8 (4.0) | 260 | |
| Vocabulary at 4 | 35.0 (6.8) | 373 | 35.0 (6.8) | 373 | — b | 0.0 | 20.7 (9.7) | 260 | |
| Restricted sample, based on one randomly selected twin from each pair | |||||||||
| Vocabulary at 2 | 10.1 (3.7) | 240 | 47.9 (19.6) | 190 | −0.26 (199.5) | < .001 | 3.5 | 9.0 (3.9) | 140 |
| Vocabulary at 4 | 35.5 (6.7) | 240 | 35.2 (6.9) | 190 | 0.53 (428) | .59 | 0.04 | 21.1 (9.5) | 140 |
| Grammar at 4 | 5.9 (0.36) | 240 | 5.9 (0.32) | 189 | −0.26 (427) | .80 | 0.0 | 4.8 (0.93) 136 | 140 |
| Language use at 4 | 9.8 (2.1) | 230 | 10.0 (0.26) | 177 | −0.88 (334.6) | .38 | 0.15 | 4.7 (2.6) | 122 |
| % maled | 62.1 | 64.2 | .36 | 70.4 | |||||
| % MZ:DZss:DZos | 40.4: 28.3: 31.3 | 41.6: 28.4: 30.0 | .65 | 41.9: 30.3: 27.7 | |||||
| SES | 0.046 (.95) | 217 | 0.040 (0.96) | 182 | 0.057 (397) | .95 | .01 | −0.26 (0.90) | 127 |
| % Family historyc,d | 3.8 | 7.4 | .13 | 3.8 | |||||
Note. MZ = monozygotic; DZss = dizygotic, same sex; DZos = dizygotic, opposite sex; SES = socioeconomic status.
a
Unequal (and nonoverlapping) by design.
b
Matched by design.
c
First-degree relative with history of language/literacy learning difficulties.
d
Fisher’s exact test, two-sided.