Too Much of a Good Thing? Positive Assortment and Social Dilemmas

When does evolution lead to efficient outcomes in a social dilemma such as the prisoner’s dilemma or stag hunt? There is a growing consensus in the literature that correlated interaction among behavioral strategies is key. Partner choice, reciprocity, kin selection, and local interactions all generate positive assortment and thus open up new evolutionary possibilities. In this brief note we contend that sometimes increasing the degree of assortment has negative consequences in social dilemmas. Namely, increased assortment can stabilize previously unobtainable inefficient outcomes.