Michael McCullough: University of Miami Department of Psychology

Exploitation—the targeted infliction of fitness costs on another organism for the purpose of capturing benefits for the self—is a fact of life for social organisms. Because of its pervasiveness in social life, natural selection gives rise to deterrence mechanisms (e.g., thorns, toxins, defensive weaponry) designed to alter potential exploiters’ estimates of the net benefits to come from exploitation. In this talk, I situate humans’ (and other social animals’) propensities to seek revenge among other naturally selected deterrence mechanisms. Revenge-based deterrence, however, can create additional costs, including those associated with lost access to valuable relationship partners. Consequently, natural selection gives rise to subsidiary mechanisms designed to (under a fairly restricted set of circumstances) inhibit revenge-based deterrence and signal a willingness to re-establish positive relations. I conceptualize these subsidiary systems as reconciliation (or forgiveness) systems. In this talk, I introduce several lines of research in which we have: (a) searched for the social conditions that revenge and forgiveness/conciliatory behavior evolved to address, (b) searched for the computations that underlie these systems, and (c) sketched out their endocrinological substrates.