Demographic characteristics of the sample at age 3 (n=622)
| Age (mean; SD) | 3.8 (0.33) |
| Sex; n (%) | |
| Male | 311 (50.0) |
| Race/ethnicity; n (%) | |
| Non-Hispanic White | 557 (89.5) |
| Hispanic-American | 46 (7.4) |
| Other | 19 (3.1) |
| Socioeconomic status; n (%) | |
| High | 205 (33.0) |
| Middle | 280 (45.0) |
| Low | 137 (22.0) |