With respect to behavior, measurement often boils down to decisions about which constellations of items, combined in which way, best characterize the salient latent behavioral outcomes and psychosocial risk factors. The relationship between the numbers generated by a test and the way genes and environment work is tenuous and theory-dependent. There is an intimate connection between the choice of measure, and conclusions drawn about the relative importance of genes, environment and the various possible interactions between them. Elegant pictures of the role of G × E interaction may be no more robust than the items selected to measure the hypothesized latent variable, the rule used to combine them, or how the scores are scaled after they have been combined.
