Since the publication of this paper in 2003, our lab has been actively involved in analyses of how poverty effects genetic variability in intelligence. That study showed that in the National Collaborative Perinatal Project, a large representative sample of mothers and their children in the US, the heritability of IQ in seven year olds was very low among the poorest twins and very high among the best off. Similar findings had been published previously by Sandra Scarr, David Rowe and Kristen Jacobson. Since that time, we have followed up on that result in many datasets. The effect appears to be replicable in US samples, but not in other Western (mostly European) nations.