It is well established that academic achievement is related to socioeconomic status (SES), but it is not yet clear at what age this effect emerges. Tucker-Drob et al. examined whether the effects of SES on mental ability could be observed in infancy. They analyzed 750 pairs of twins from the Early Childhood Longitudinal Study, Birth Cohort data file. At 10 months and 2 years of age, the children's mental ability was assessed using tests that included pulling a string to ring a bell, putting cubes in a cup and matching pictures, among other tasks. SES was determined from the education and occupations of the parents and family income.
At 10 months of age, SES was not related to mental ability. Between 10 months and 2 years of age, however, the authors observed that increased SES was associated with larger gains in mental ability. At 2 years of age, the influence of genetics on cognitive development was higher in children of higher SES, whereas genetics had very little effect on the mental ability of children raised in low-SES homes. These findings do not indicate any differences in intrinsic intelligence, but may provide support for efforts to provide enrichment for young children from disadvantaged backgrounds.
Psychol. Sci. 22, 125 (2011).