we WEIRD ones typically practise what is known as ‘strong reciprocity’: we are conditional cooperators (tending to cooperate so long as others do too) but also altruistic punishers (ready to punish defectors and free riders even if it costs us personally). And it is the combination of these two traits that leads to the success of large-scale cooperation in society.23 No wonder rating and review systems are so popular in the otherwise anonymous online marketplace.
