  How can societies learn to enforce and comply with social norms? Here we
investigate the learning dynamics and emergence of compliance and enforcement
of social norms in a foraging game, implemented in a multi-agent reinforcement
learning setting. In this spatiotemporally extended game, individuals are
incentivized to implement complex berry-foraging policies and punish
transgressions against social taboos covering specific berry types. We show
that agents benefit when eating poisonous berries is taboo, meaning the
behavior is punished by other agents, as this helps overcome a
credit-assignment problem in discovering delayed health effects. Critically,
however, we also show that introducing an additional taboo, which results in
punishment for eating a harmless berry, improves the rate and stability with
which agents learn to punish taboo violations and comply with taboos.
Counterintuitively, our results show that an arbitrary taboo (a "silly rule")
can enhance social learning dynamics and achieve better outcomes in the middle
stages of learning. We discuss the results in the context of studying
normativity as a group-level emergent phenomenon.
