We view longitudinal, genetically informative studies that assess individuals’ personal characteristics and preferences, plausible biological endophenotypes of personality, the social environment, the macro-environmental resources available, and important life events as crucial to the success of ongoing personality research. Although a number of empirical examples of gene-environment interplay can be found in the literature, longitudinal extensions of these designs are infrequent. Are gene-by-environment interactions lasting or fleeting? Are they only active during certain critical periods of development? Addressing these questions requires not only identifying gene-environment interplay, but also tracking the effects through time (e.g., Rhemtulla & Tucker-Drob, 2012).
