The Early Childhood Longitudinal Study Birth Cohort (ECLS-B) is the first large, nationally representative sample with measures of mental functioning for children age one and under. Analyzing these data, Roland G. Fryer, Jr. and Steven D. Levitt find extremely small racial differences in mental functioning of children age 8 to 12 months. Accounting for a few more characteristics like the child’s age, gender, socioeconomic status, home environment, and prenatal circumstances further reduces the racial differences. However, measuring the test score gap as age progresses paints a different picture.