critique of a recent ajs genetics paper: levi-martin v. guo, li, wang, cai and duncan
John Levi-Martin has written a comment on a recent paper by Guo, Li, Wang, Cai, and Duncan claiming that the social contagion of binge drinking associated with a medium genetic propensity. Levi-Martin claims that GLWCD having simply misread their data:
Guo, Li, Wang, Cai and Duncan (2015) recently claimed to have provided evidence for ageneral theory of gene-environment interaction. The theory holds that those who are labelled as having high or low genetic propensity to alcohol use will be unresponsive to environmental factors that predict binge-drinking among those of moderate propensity. They actually demonstrate evidence against their theory, but do not seem to have understood this.
This is consequential because of the way that choose to examine their data. Althoughthe verbal description of the swing theory here refers to the comparison of magnitudes (“more likely”), the methods used by GLWCD involve successive tests of the null hypothesis across three subsets formed by partitioning the sample by level of what is termed genetic propensity. If we denote these three subsets L, M and H, standing for low, medium and high propensity, then, for the kth predictor, they estimate three slopes, bLk, bMk, and bHk. Because the swing theory does not require that any particular predictor have an effect, but only that if it does, it does not in the extreme propensity tiers, this theory holds that for any k, bLk≈bHk≈ 0.