Reply to Turkheimer and Waldron and Wahlsten

Abstract

To gain an overall picture of the role of the various sources that play a part in human development, it is surely in order to abstract from the intricate relations between genes, experience, and the environment. And surely there is no reason to suppose that one cannot learn something by using simplified models. Using an additivity model in a case where one knows that reality is interactive and complex (e.g., when the genesis of specific mental traits are at issue), one can still get a clue whether a particular variable makes a difference in a population and estimate the sence of its importance. But, as I argued in my paper, it is quite another thing to make causal inferences, such as saying that genes and the unshared environment are largely responsible for the enduring features of our mental life, such as intelligence, personality, one’s likes and dislikes, while the shared environment has hardly any causal effect on these traits. These conclusions, so I argued, are one station too far. It seems to me that making those inferences does require extra assumptions, and if these are not provided or are unavailable, one must settle for less grandiose conclusions. Turkheimer and Waldron seem to agree, or don’t they? They acknowledge that correlational statistical methods, as such, do not bear developmental conclusions. But they see this as a truth, which applies to all correlation-based studies. According to them, there is no difference between behavioral genetics use of the ANOVA method and its use in developmental psychology or any other field. So they object to my addressing