title: Resilient cooperators stabilize long-run cooperation in the finitely repeated Prisoner's Dilemma.
abstract: Learning in finitely repeated games of cooperation remains poorly understood in part because their dynamics play out over a timescale exceeding that of traditional lab experiments. Here, we report results of a virtual lab experiment in which 94 subjects play up to 400 ten-round games of Prisoner's Dilemma over the course of twenty consecutive weekdays. Consistent with previous work, the typical round of first defection moves earlier for several days; however, this unravelling process stabilizes after roughly one week. Analysing individual strategies, we find that approximately 40% of players behave as resilient cooperators who avoid unravelling even at significant cost to themselves. Finally, using a standard learning model we predict that a sufficiently large minority of resilient cooperators can permanently stabilize unravelling among a majority of rational players. These results shed hopeful light on the long-term dynamics of cooperation, and demonstrate the importance of long-run experiments.
authors.affiliation: Microsoft Research, 641 Avenue of the Americas, 7th Floor, New York, New York 10011, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Mao
authors.affiliation: Socratic.org, 1133 Broadway, Suite 423, New York, New York 10010, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Dworkin
authors.affiliation: Microsoft Research, 641 Avenue of the Americas, 7th Floor, New York, New York 10011, USA.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Suri
authors.affiliation: Microsoft Research, 641 Avenue of the Americas, 7th Floor, New York, New York 10011, USA.
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Watts
mesh_terms: D000293:Adolescent; D000328:Adult; D003299:Cooperative Behavior; D003657:Decision Making; D005260:Female; D005716:Game Theory; D006801:Humans; D007858:Learning; D008297:Male; D008875:Middle Aged; D000068956:Prisoner Dilemma; D055500:Resilience, Psychological; D055815:Young Adult