Rationality, the Prisoner's Dilemma, and Population¹

The growth of human populations as a function of the desire on the part of parents to have a greater number of children (on the average) than the number needed for a steady state (zero population growth) is analyzed within the framework of the prisoner's dilemma game, a model that has enjoyed considerable popularity among social scientists in recent years. Proposed resolutions of the prisoner's dilemma are translated into analogous situations in the population growth problem. A proposed solution is the adoption of an interactive rationality, where families consider their own decisions in light of their existence in common with other families. In this way, family size becomes another part of life governed by social contract as well as individual desire.