‘Social lives’ explores some of the main ways in which social influences drive behaviour, including aversion to unequal outcomes, trust and reciprocity, social learning, and peer pressure. The interplay between trust and reciprocity is a key element in many of the cooperative and collaborative activities that we undertake daily. There are two main types of inequity aversion: disadvantageous and advantageous. Social norms are another set of social influences that drive our behaviour, and these are often reinforced through peer pressure. They help to explain how and why we have evolved as a cooperative species, but how do we ensure that no-one free rides on others’ generosity?