The New York Times has an excellent article about the whole nature-nurture IQ controversy (NY Times only makes articles available free for a very short time, so get in quick if you want to read it). It talks about the infamous Bell Curve book by Herrnstein & Murray, which essentially made the case justifying not bothering to intervene for disadvantaged children because genes were all powerful.

Readers of my blog and newsletters will know this is not a point of view I hold! and moreover, that a number of studies have come out in recent times demonstrating just how important the interaction of genes and environment is. This article discusses some particularly important studies that have now been done, overcoming the methodological flaws of earlier studies.

Herrnstein & Murray's case rested on IQ comparisons from 2 sources -- twin studies, and adoption studies. The problem is that twin studies generally have examined twins from middle-class backgrounds -- because this is where most volunteers come from. And the adoption studies have generally involved children from poorer backgrounds being adopted by people from wealthier backgrounds -- because this is how most adoptions work.

However, it turns out that if you look at IQ scores of twins from poor backgrounds, you find that in fact the IQs of identical twins vary just as much as those of fraternal twins. And if you look at those rare children who were born to better-off parents, and adopted by poorer families, you find that their IQ is indeed affected by the environment into which they are adopted.

Actually. the statistics are quite alarming -- children from a well-off family adopted into a similarly well-off family had an average IQ of 119.6, but only 107.5 if adopted by poor families. And in children adopted when between 4 and 6, when they had already been disadvantaged through those all-important early years, and had an average IQ of 77 (borderline retardation), being adopted into a wealthy home raised their IQ to an average of 98! But those adopted into poorer homes only increased to 85.5.

Interestingly, I was reading this right after reading about a just-published study that has discovered 3 genes that are associated with rheumatoid arthritis. While these genes are expressed in those with the disease, they are not expressed in the genetically-identical twin if said twin doesn't have the disease. In other words, as researchers keep finding, genes are not destiny. It's the environment (sometimes the prenatal environment) that affects whether or not the genes are expressed.