Recently, two research teams advanced a different theoretical model, differential-susceptibility (Belsky, 1997, 2005; Boyce & Ellis, 2005; Ellis, Boyce, Belsky, Bakermans-Kranenburg & Van IJzendoorn, 2011). Differential-susceptibility also leads to prediction of a GXE interaction, but one disordinal in form. Under differential-susceptibility, persons carrying a so-called risk allele may simply be more malleable. From this perspective (and in accord with diathesis stress), persons with a putative high-risk allele should exhibit poorer outcomes in poor environments and similar outcomes to persons with a low-risk allele in average environments. However, the model suggests that, in very good environments, persons with a putative high-risk allele will show outcomes that are superior to persons with the low-risk allele. This theoretical conceptualization leads to prediction of the disordinal, or cross-over, interaction in Figure 1B. Thus, diathesis-stress and differential susceptibility theories make identical predictions about the differing slopes for the two gene allele groups; what distinguishes predictions under the two models is the location of the cross-over point (cf.Figure 1).
