Evolution of the wealth gap in child development and mediating pathways: Evidence from a longitudinal study in...

Large gaps in cognition and language on the Bayley-III between the top and bottom household wealth quartiles in 1,330 children aged 6-42 months in a representative sample of low- and middle-income families in Bogota were previously shown. Maternal education and the home environment mediated these wealth effects, whereas height-for-age mediated a small amount of the language deficit only. At ages 6-8 years, we relocated 72% of the children and assessed their IQ on the WISC-V, school achievement, and behavior to investigate the evolution of the wealth gaps and potential mediators. The wealth gap in IQ at 6-8 years was significantly larger than that in a factor combining Bayley-III language and cognition at 6-42 months; whereas the gap in achievement was larger but not significantly. Moreover, in cross-sectional analysis, the IQ gap increased from 6 to 8 years reaching over 1 SD. In contrast, the gap in behavior was not significant in either childhood stage. Parental education and early home environment remained major mediators of the wealth gap in IQ and achievement at 6-8 years; later home environment and attending private education also had an effect; and early height-for-age was no longer significant. The home environment partly mediated the effect of parental education on wealth. All mediators combined explained most of the variance in the wealth gap; the remaining gaps being not significant. Results highlight the importance of the early home environment and suggest that interventions focusing on that should have long-term benefits. Also, continued intervention through to 8 years may be desirable. A video abstract of this article can be viewed at https://youtu.be/_U53iXNww3I.