Previous research has discovered a curious phenomenon: groups cooperate less than individuals in a deterministic prisoner’s dilemma game, but cooperate more than individuals when uncertainty is introduced into the game. We conducted two studies to examine three possible processes that might...

Previous research has shown an interindividual-intergroup discontinuity effect: intergroup interactions generally lead to less cooperative outcomes than interindividual interactions. We replicated the discontinuity effect in the deterministic prisoners dilemma, but we found that groups were more...

Subjects were less willing to pay for government medical insurance for diseases when the number of people who could not be cured was higher, holding constant the number who could be cured. In a second experiment, willingness to pay (from a hypothetical government windfall) for risk reduction was...