Causation in the nature-nurture debate: The case of genotype-environment interaction.

摘要

I attempt to resolve an aspect of the nature-nurture debate. Consider a typical nature-nurture question: Why do some individuals develop a complex trait such as depression, while others do not? This question incorporates an etiological query about the causal mechanisms responsible for the individual development of depression; it also incorporates an etiological query about the causes of variation responsible for individual differences in the occurrence of depression. Scientists in the developmental research tradition of biology investigate the former; scientists in the biometric research tradition of biology investigate the latter. So what is the relationship?;The developmental and biometric research traditions, I argue, are united in their joint effort to elucidate what I call difference mechanisms. Difference mechanisms are regular causal mechanisms made up of difference-making variables that take different values in the natural world. On this model, individual differences are the effect of difference-makers in development that take different values in the natural world.;I apply this model to the case of genotype-environment interaction (or GxE), showing that there have actually been two separate concepts of GxE: a biometric concept (or GxEB) and a developmental concept (or GxED). These concepts also may be integrated via the difference mechanisms model: GxE results from the interdependence of difference-makers in development that take different values in the natural world.