Sadly, the fact that the approach, and John Loehlin’s early critical insight, lie all but forgotten by the contemporary literature means a fundamental lesson from quantitative genetics appears not to have been internalized by the new generation of behavioral researchers competing for the prestige and funding that goes with the pursuit of G × E in psychiatric genetics. The apparently forgotten lesson from those early efforts is quite simple. You can generate almost any interaction you want by changing the scale of measurement. The implication is equally simple: Don’t make a career out of your interaction until you have excluded simpler psychometric considerations that owe nothing to the subtleties of the underlying genetic and environmental causes of human variation.
