title: Do we harm others even if we don't need to?
abstract: Evolutionary explanations of the co-existence of large-scale cooperation and warfare in human societies rest on the hypothesis of parochial altruism, the view that in-group pro-sociality and out-group anti-sociality have co-evolved. We designed an experiment that allows subjects to freely choose between actions that are purely pro-social, purely anti-social, or a combination of the two. We present behavioral evidence on the existence of strong aggression-a pattern of non-strategic behaviors that are welfare-reducing for all individuals (i.e., victims and perpetrators). We also show how strong aggression serves to dynamically stabilize in-group pro-sociality.
authors.affiliation: Department of Economics, University of Lausanne Lausanne, Switzerland.
authors.forename: M Paula
authors.initials: MP
authors.lastname: Cacault
authors.affiliation: Department of Economics, University of Lausanne Lausanne, Switzerland.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Goette
authors.affiliation: Department of Economics, University of Lausanne Lausanne, Switzerland.
authors.forename: Rafael
authors.initials: R
authors.lastname: Lalive
authors.affiliation: Department of Economics, University of Lausanne Lausanne, Switzerland.
authors.forename: Mathias
authors.initials: M
authors.lastname: Thoenig
keywords: experimental tests; in-group favoritism; out-group aggression; parochial altruism; public-good; strong aggression