We have studied many choices: Anna’s choice between housing and other things, Brian’s choice between pizza and beer, and Anna’s choice between consumption and leisure. The starting point has always been that consumers do the best they can with the money they have and the prices they face in the market. Preferences are stable, and they maximise their utility. In other words: consumers are rational. Moreover, they are solely concerned with their own consumption when making choices: they are selfish. We call this type homo economicus, the economic man. In this chapter, I give you some glimpses of behavioural economics, using the modelling framework we have developed so far so that you can more easily see how this perspective relates to traditional theory. The chapter begins with saving and how temptations can lead us to deviate from our long-term plans. I then introduce loss aversion and show how it can affect labour supply. Finally, we analyse how Brian’s mother decides how much to give her son, based on altruistic preferences.