Decoupling cooperation and punishment in humans shows that punishment is not an altruistic trait

Abstract

Economic experiments have suggested that cooperative humans will altruistically match local levels of cooperation (conditional cooperation) and pay to punish non-cooperators (altruistic punishment). Evolutionary models have suggested that if altruists punish non-altruists this could favour the evolution of costly helping behaviours (cooperation) among strangers. An often-key requirement is that helping behaviours and punishing behaviours form one single conjoined trait (strong reciprocity). Previous economics experiments have provided support for the hypothesis that punishment and cooperation form one conjoined, altruistically motivated, trait. However, such a conjoined trait may be evolutionarily unstable, and previous experiments have confounded a fear of being punished with being surrounded by cooperators, two factors that could favour cooperation. Here, we experimentally decouple the fear of punishment from a cooperative environment and allow cooperation and punishment behaviour to freely separate (420 participants). We show, that if a minority of individuals is made immune to punishment, they (i) learn to stop cooperating on average despite being surrounded by high levels of cooperation, contradicting the idea of conditional cooperation and (ii) often continue to punish, ‘hypocritically’, showing that cooperation and punishment do not form one, altruistically motivated, linked trait.

A preference to learn from successful rather than common behaviours in human social dilemmas

“…If individuals observe declining levels of cooperation, it is hard to test if individuals are learning from success or trying to match a declining group average [36,50]. Our solution was to show participants data from one of our own previous experiments that used peer punishment to stabilize mean contributions [66]. This meant that if contributions declined in this current study, this could not be attributed to individuals attempting to match, even imperfectly, the Common pattern [33,36,39].…”

“…Although punishment is often part of gene-culture coevolutionary theories, it is important to realize that our use of punishment is not a key feature of this experiment (in fact, our original plan was to show data from an experiment with a 'noinformation' treatment, but we subsequently found the punishment data to be slightly more stable [50,66]). Our participants in this study were not aware that punishment was a feature of the previous experiment.…”

Social learning disfavours the cultural evolution of altruistic punishment

“…Whether this would be to the benefit of the whole group, rather than just the elites, is unclear 22,23 . Of course, another possibility is that natural punishment is not altruistic 6,[24][25][26][27][28][29][30][31][32][33] .…”

“…Consequently, it has been hypothesized that human cooperation is the evolutionary result of group selection favouring groups with altruistic punishment [1][2][3]7,8,10,[12][13][14][15] . However, the same experiments which show that 'altruistic punishment' can sustain cooperation, also show that altruistic punishment is net costly for groups, challenging group level explanations 1,5,6 . Quite simply, the costs of punishment in such experiments, where individuals pay to reduce the earnings of noncooperators, tend to outweigh the benefits gained from increased cooperation 1,5,6 .…”

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Could human cooperation be the result of evolution favouring groups where altruists punish non-altruists [1][2][3][4] ? While punishment can benefit groups through increased cooperation, it often costs more than it is worth, challenging group level explanations 1,5,6 . We therefore tested if altruistic punishment could spread among groups via imitation (social learning) rather than direct competition.

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