Mean scores on the Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI) of the Bayley Scales of Infant Development (Bayley, 1993) for infants in the concordant-favorability, postnatal-only-adversity, prenatal-only-adversity, and concordant-adversity groups. The three panels on the left present the mean MDI scores for (a) 3-month-old, (b) 6-month-old, and (c) 12-month-old infants, and the three panels on the right present the mean PDI scores for (d) 3-month-old, (e) 6-month-old, and (f) 12-month-old infants. The p values indicate significant differences between the concordant and the discrepant groups. Error bars indicate standard errors of the mean.