Behavioural economics is the study of how people make decisions in a complex and textured world where details matter. It draws from the fields of economics and psychology, but brings a unique perspective that departs from each of these fields in important ways. behavioural economics differs from standard economics because it uses a more realistic (and more complex) model for how we view people. It differs from psychology because it maintains a focus on institutions and the contexts in which decisions are made. To apply lessons from behavioural economics research, the BETA Project adopts ideas42’s behavioural Diagnosis and Design methodology to help identify the barriers that impede desired behaviours and outcomes.