Table 1.

Participant characteristics

CharacteristicGroupDifference
MaleFemale
Number of individuals328319
Handedness, nn.s
    Right282275
    Non-right4644
Race, nn.s
    Caucasian270269
    African-American3227
    Asian86
    Hispanic812
    Other105
Singleton, n208198n.s
Member of twin pair, n120121
    Dizygotic5962
    Monozygotic6159
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
    1133138
    2103113
    ≥39268
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)
    Range3.3–313.7–30.3
  • SES, Socioeconomic status; n.s., not significant.