Fired with enthusiasm for this insight, and challenged by David who had thought a lot about G × E and risk to psychopathology, we embarked on an exploration of G × E for personality applying the “Jinks and Fulker” approach to some early “EPQ” data on twins that Hans Eysenck had generously shared. Very soon I had generated some pretty diagrams and David had written the first draft of a joint paper showing significant, complex, non-linear, G × E for personality test scores. Recollection is hazy, but I think David sent an early draft to John Loehlin who suggested that we should check whether the interaction was “really” G × E or whether it was just a function of variation in measurement error over the range of test scores. “Goodbye” to a good paper, part of my doctoral dissertation and, for all intents and purposes, to a promising method since very few applications of the approach have been published in the 40 years since it first appeared.
