Participant demographics
| Group 1 | Group 2 | Group 3 | Group 4 | |
| Mean | 6.47(0.81) | 9.16(0.76) | 12.04(0.84) | 16.03(1.27) |
| Age range (years) | 4.80-7.85 | 8.02-10.47 | 10.68-13.50 | 13.99-18.35 |
| Mean IQ (SD) | 110.9(16.0) | 112.5(12.9) | 112.1(10.7) | 109.0(11.4) |
| IQ range | 79-156 | 77-160 | 84-131 | 78-132 |
| Handedness R:L | 83:7 | 80:10 | 80:10 | 81:9 |
| Gender M:F | 45:45 | 45:45 | 45:45 | 45:45 |
| Mean adjusted income Thousands (SD) | 71.1(32.5) | 70.0(30.6) | 70.1(32.0) | 70.0(31.4) |