At 10 months, no difference between kids in high and low SES families - by age 2, rich kids score 1/3 SD higher
Via Freddie deBoer’s tremendous new blog on education, a nice summary:
"However, recent evidence from the United States indicates that hereditary factors are not a major constraint for low SES students (Nisbett et al., 2012). For example, Tucker-Drob, Rhemtulla, Harden, Turkheimer, and Fask (2011) found no significant differences between children in high and low SES families on the Bayley Short Form–Research Edition (see, e.g., Andreassen & Fletcher, 2007)—a test of infant mental ability—at the age of 10 months, but by age 2 children in high SES families scored about one third of a standard deviation higher than children in low SES families. Genes accounted for nearly 50% of the variation in mental ability of high SES children but only a negligible share of low SES children’s variation, indicating that the latter are not reaching their full cognitive potential. Rhemtulla and Tucker-Drob (2012) found similar patterns of gene and SES interactions in follow-up tests of mathematics skill at age 4 (but no significant interactions in reading). Fryer and Levitt (2013) found no significant differences on the Bayley Short Form–Research Edition among Hispanic, Asian, Black, and White infants aged 8 to 12 months, although a one standard deviation gap in test scores between Black and White children, which typically differ in SES, has been observed by age 3."
Link to the paper here.