Data and files for: Decoupling cooperation and punishment in humans shows that punishment is not an altruistic trait

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 are made immune to punishment, they (1) learn
to stop cooperating on average despite being surrounded by high levels of
cooperation, contradicting the idea of conditional cooperation; and (2)
often continue to punish, ‘hypocritically’, showing that cooperation and
punishment do not form one, altruistically motivated, linked trait.