Table 3.
Intraclass twin correlations (ICC) and proportion of variance due to genetic (A), shared environmental (C), and nonshared environmental (E) factors for reading achievement and independent reading (with 95% confidence intervals in parentheses)
MZ | DZ | Variance components | ||||
---|---|---|---|---|---|---|
| ||||||
ICC | n | ICC | n | A | E | |
Print 1 | .59 (.42, .72) |
73 | .00 (.00, .17) |
93 | .62 (.45, .73) |
.38 (.27, .55) |
Read1 . | 88 (.81, .92) |
81 | .42 (.25, .57) |
104 | .90 (.85, .92) |
.10 (.08, .15) |
Print 2 | .61 (.40, .76) |
48 | .00 (.00, .21) |
61 | .55 (.36, .68) |
.45 (.32, .64) |
Read2 | .77 (.65, .86) |
61 | .47 (.28, .62) |
79 | .75 (.69, .80) |
.25 (.20, .31) |
Note: n = Number of pairs. MZ = Monozygotic twins; DZ = Dizygotic twins. Read1, Print1 = reading achievement and independent reading at Age 10; Read2, Print2 = reading achievement and independent reading at Age 11.