Can a simple nudge change behaviour for the common good - even in potentially life and death situations? Elizabeth Hotson talks to Helena Rubenstein, Head of Behavioural Science of Innovia Technology, about a successful experiment to stop drink driving and Martine Visser, economics professor at the university of Cape Town, explains how nudging the inhabitants of South Africa’s most populous city to use less water, averted Day Zero. Plus Erez Yoeli, a research associate in altruism at MIT tells us how selfish people can be persuaded to act in everyone’s best interests. And Ravi Gurumurthy CEO of charity, Nesta, explains how the Behavioural Insights Team applies behavioural science to public policy. Produced by Sarah Treanor. (Picture of bing soo by Elizabeth Hotson).