In a critique of Brink Lindsey, Arnold writes: “I think that my co-blogger would go ballistic over this ‘nurture assumption’ methodology.” I wouldn’t quite go ballistic, because there is solid evidence that growing up in a high-IQ home raises the IQs of adopted children. However, this IQ gain does not last. By the time he’s 18, the correlation between an adoptee’s IQ and the IQ of the family that adopted him is zero.

In short, parents are correct to think that they can change their children. Their mistake is to suppose that the change will endure. Instead of thinking of kids as lumps of clay that parents “mold,” we should think of kids as plastic that flexes in response to pressure – and springs back to its original shape once the pressure goes away.