Why is there so much interest in behavioural economics and how is it different? ‘Economics and behaviour’ explains how behavioural economists bring economics together with insights from other disciplines, such as psychology, sociology, neuroscience, and evolutionary biology. Using this multidisciplinary approach, behavioural economists enrich our understanding of economic and financial behaviour, without necessarily abandoning the analytical power often associated with conventional economics. Behavioural economists assume there are some limits to rational decision-making and draw on the concepts of bounded, ecological, and selective rationality. Behavioural economists also need to find relevant and reliable data including experimental and neuroscientific data. Natural experiments and randomized controlled trials are explained.