The traditional narrative says we need to shift a person’s attitudes before we can change their behaviour. But behavioural science shows us that people’s attitudes can shift to better align with their behaviour. So which is it? Alexandra De Filippo (BIT), Sonia Whitehead (BBC), Benjamin Kumpf (DfID), Katherine Rodrigues (International Rescue Committee) and Pippa Yeats (Turn.io) investigate at BX2019.