Discounting and Reciprocity in an Iterated Prisoner's Dilemma
D. W. Stephens,*
C. M. McLinn,
J. R. Stevens
The Iterated Prisoner's Dilemma (IPD) is a central
paradigm in the study of animal cooperation. According to the IPD
framework, repeated play (repetition) and reciprocity combine to
maintain a cooperative equilibrium. However, experimental studies with animals suggest that cooperative behavior in IPDs is unstable, and some
have suggested that strong preferences for immediate benefits (that is,
temporal discounting) might explain the fragility of cooperative
equilibria. We studied the effects of discounting and strategic
reciprocity on cooperation in captive blue jays. Our results
demonstrate an interaction between discounting and reciprocity. Blue
jays show high stable levels of cooperation in treatments with reduced
discounting when their opponent reciprocates, but their levels of
cooperation decline in all other treatment combinations. This suggests
that stable cooperation requires both reduced discounting and
reciprocity, and it offers an explanation of earlier failures to find
cooperation in controlled payoff games.
Department of Ecology, Evolution and Behavior, University of
Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, USA.
*
To whom correspondence should be addressed. E-mail:
dws{at}forager.cbs.umn.edu
