title: Cooperate without looking: why we care what people think and not just what they do.
abstract: Evolutionary game theory typically focuses on actions but ignores motives. Here, we introduce a model that takes into account the motive behind the action. A crucial question is why do we trust people more who cooperate without calculating the costs? We propose a game theory model to explain this phenomenon. One player has the option to "look" at the costs of cooperation, and the other player chooses whether to continue the interaction. If it is occasionally very costly for player 1 to cooperate, but defection is harmful for player 2, then cooperation without looking is a subgame perfect equilibrium. This behavior also emerges in population-based processes of learning or evolution. Our theory illuminates a number of key phenomena of human interactions: authentic altruism, why people cooperate intuitively, one-shot cooperation, why friends do not keep track of favors, why we admire principled people, Kant's second formulation of the Categorical Imperative, taboos, and love.
authors.affiliation: Program for Evolutionary Dynamics, Department of Mathematics and.
authors.forename: Moshe
authors.initials: M
authors.lastname: Hoffman
authors.affiliation: Program for Evolutionary Dynamics, Department of Mathematics and.
authors.forename: Erez
authors.initials: E
authors.lastname: Yoeli
authors.affiliation: Program for Evolutionary Dynamics, Department of Mathematics and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138 martin_nowak@harvard.edu.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Nowak
mesh_terms: D000533:Altruism; D005075:Biological Evolution; D003299:Cooperative Behavior; D003362:Cost-Benefit Analysis; D005716:Game Theory; D006801:Humans; D008960:Models, Psychological; D009042:Motivation; D035502:Trust / Q000523:psychology*
keywords: cooperation; emotion; evolution; game theory; motive