Table 1.

Participant characteristics

Number of individuals328319
Handedness, nn.s
Race, nn.s
Singleton, n208198n.s
Member of twin pair, n120121
IQ, mean (SD)113 (12.7)112 (12.3)n.s
SES (SD)43 (19.5)43 (18.9)n.s
Total number of scans667607
Number of scans, nn.s
Age at each scan in years, mean (SD)
    First scan11.6 (4.7)11.7 (5.1)n.s
    Second scan13.5 (4.4)13.2 (4.2)n.s
    Third scan15.5 (3.9)14.5 (4.0)n.s
Age distribution of scans, years
    Mean (SD)12.8 (4.9)13.2 (5.1)
  • SES, Socioeconomic status; n.s., not significant.