Table 3.
Intraclass Correlations among Learning and Literacy Variables
|
A. Monozygotic twins
| ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Twin 1 | Twin 2 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| 1. WRAML Story memory | .48 | |||||||||||
| 2. WRAML Sound-symbol | .23 | ..31 | ||||||||||
| 3. Nonword repetition | .22 | .26 | .56 | |||||||||
| 4. WPPSI Sentence memory | .33 | .27 | .45 | .71 | ||||||||
| 5. Hundred pictures | .41 | .27 | .27 | .44 | .76 | |||||||
| 6. WPPSI Vocabulary | .36 | .26 | .34 | .43 | .47 | .58 | ||||||
| 7. Boston naming | .30 | .18 | .23 | .43 | .66 | .38 | .82 | |||||
| 8. Letter identification | .18 | .26 | .22 | .31 | .38 | .26 | .37 | .76 | ||||
| 9. Orthographic learning | .09 | .17 | .18 | .13 | .13 | .10 | .17 | .22 | .61 | |||
| 10. TOWRE SWE | .16 | .20 | .17 | .21 | .20 | .17 | .26 | .30 | .50 | .81 | ||
| 11. TOWRE PDE | .09 | .15 | .15 | .23 | .15 | .12 | .23 | .28 | .53 | .76 | .80 | |
|
B. Dizygotic twins
| ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Twin 1 | Twin 2 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| 1. WRAML Story memory | .27 | |||||||||||
| 2. WRAML Sound-symbol | .09 | .17 | ||||||||||
| 3. Nonword repetition | .13 | .11 | .34 | |||||||||
| 4. WPPSI Sentence memory | .26 | .13 | .27 | .47 | ||||||||
| 5. Hundred pictures | .27 | .18 | .24 | .34 | .62 | |||||||
| 6. WPPSI Vocabulary | .26 | .18 | .29 | .36 | .35 | .51 | ||||||
| 7. Boston naming | .16 | .17 | .24 | .29 | .52 | .28 | .59 | |||||
| 8. Letter identification | .14 | .16 | .19 | .26 | .36 | .27 | .34 | .68 | ||||
| 9. Orthographic learning | .02 | .09 | .10 | .11 | .13 | .09 | .18 | .19 | .32 | |||
| 10. TOWRE SWE | .07 | .12 | .14 | .14 | .22 | .18 | .22 | .23 | .30 | .43 | ||
| 11. TOWRE PDE | .05 | .12 | .15 | .14 | .20 | .18 | .21 | .21 | .30 | .41 | .43 | |
Note: Cross-twin, within trait correlations on diagonals in bold, cross-twin, cross-trait correlations off diagonals. WRAML = Wide Range Assessment of Memory and Learning; TOWRE SWE= Test of Word Reading Efficiency, Sight Word Efficiency; TOWRE PDE= Test of Word Reading Efficiency, Phonemic Decoding Efficiency; WPPSI = Wechsler Preschool and Primary Scale of Intelligence.