Why do some people get involved while others stand by looking on? What makes people act for the sake of others? Kirsty Wark discusses the psychology of behaviour with Catherine Sanderson and David Halpern.

In the Bystander Effect, Catherine Sanderson argues that the question of why some people act badly while others are heroic is not simply about good and bad. Our brains are hard-wired to conform and to avoid social embarrassment. But there are practical measures that can help create a sense of personal responsibility, turning a silent bystander into a model of action.

The psychologist David Halpern is also interested in how to change behaviour. He is advising the UK Government on its response to the coronavirus pandemic, focusing on how to get the public to adopt new social norms, including increased hand-washing and social distancing. Halpern is the Chief Executive of the Behavioural Insights Team, unofficially known as The Nudge Unit.

Producer: Katy Hickman