title: Coaction versus reciprocity in continuous-time models of cooperation.
abstract: Cooperating animals frequently show closely coordinated behaviours organized by a continuous flow of information between interacting partners. Such real-time coaction is not captured by the iterated prisoner's dilemma and other discrete-time reciprocal cooperation games, which inherently feature a delay in information exchange. Here, we study the evolution of cooperation when individuals can dynamically respond to each other's actions. We develop continuous-time analogues of iterated-game models and describe their dynamics in terms of two variables, the propensity of individuals to initiate cooperation (altruism) and their tendency to mirror their partner's actions (coordination). These components of cooperation stabilize at an evolutionary equilibrium or show oscillations, depending on the chosen payoff parameters. Unlike reciprocal altruism, cooperation by coaction does not require that those willing to initiate cooperation pay in advance for uncertain future benefits. Correspondingly, we show that introducing a delay to information transfer between players is equivalent to increasing the cost of cooperation. Cooperative coaction can therefore evolve much more easily than reciprocal cooperation. When delays entirely prevent coordination, we recover results from the discrete-time alternating prisoner's dilemma, indicating that coaction and reciprocity are connected by a continuum of opportunities for real-time information exchange.
authors.affiliation: Institute of Ecology and Evolution, University of Bern, Wohlenstrasse 50a, CH-3032 Hinterkappelen, Switzerland; Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands. Electronic address: g.s.van.doorn@rug.nl.
authors.forename: G Sander
authors.initials: GS
authors.lastname: van Doorn
authors.affiliation: Institute of Ecology and Evolution, University of Bern, Wohlenstrasse 50a, CH-3032 Hinterkappelen, Switzerland. Electronic address: thomas.riebli@iee.unibe.ch.
authors.forename: Thomas
authors.initials: T
authors.lastname: Riebli
authors.affiliation: Institute of Ecology and Evolution, University of Bern, Wohlenstrasse 50a, CH-3032 Hinterkappelen, Switzerland. Electronic address: michael.taborsky@iee.unibe.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Taborsky
mesh_terms: D005717:Games, Experimental; D006801:Humans; D008962:Models, Theoretical; D012919:Social Behavior
keywords: Cooperative coordination; Evolutionary game theory; Information transfer; Reciprocal altruism; Social dilemmas