Demographic characteristics of the sample
| MZ | DZ | Siblings of twins | Singletons | Total | |
|---|---|---|---|---|---|
| Sample size | 222 | 101 | 84 | 270 | 677 |
| Mean ± SD age (years) | 12.55 (3.30) | 12.24 (3.29) | 12.98 (3.96) | 12.95 (4.62) | 12.72 (3.95) |
| Gender | 103 F | 46 F | 48 F | 126 F | 323 F |
| 119 M | 55 M | 36 M | 144 M | 354 M | |
| Handedness | 193 R | 83 R | 67 R | 241 R | 584 R |
| 15 M | 10 M | 7 M | 18 M | 50 M | |
| 13 L | 8L | 9 L | 11 L | 41 L | |
| FSIQ | 110.45 (11.68) | 111.71 (11.88) | 113.93 (12.55) | 115.95 (12.06) | 113.22 (12.19) |