Table 1.
Demographic breakdown of monozygotic twins (MZ), dizygotic twins (DZ), and non‐twin siblings from the subset data of the HCP, including averages and standard deviation (± SD)
| N | Average age (year ± SD) | Age range | Gender female: male | Average handedness (± SD) | Average fluid intelligence (± SD) | |
|---|---|---|---|---|---|---|
| MZ | 100 | 29.97 (3.11) | 22–36 | 74:26 | 72.4 (41.76) | 16.26 (4.64) |
| DZ | 94 | 29.86 (2.93) | 22–35 | 67:27 | 63.19 (46.06) | 16.71 (4.81) |
| Non‐twin siblings | 271 | 28.75 (3.72) | 22–36 | 136:135 | 63.56 (48.06) | 16.12 (5.11) |
| Total | 465 | 29.24 (3.49) | 22–36 | 277:188 | 65.39 (46.42) | 16.27 (4.95) |
Average fluid intelligence is a measure of number of correct responses out of 24 questions.