‘Smoking, online gambling, shooting heroin, nail biting. A daily glass of wine, as enjoyed by so many academics. Using social media. It’s all much the same,’ says Arie Dijkstra, Professor in the Social Psychology of Health and Illness, specializing in the psychology of health behaviour and addiction. ‘They are all types of behaviour that become disproportionately important to some people, at which point, behavioural psychology calls it addiction.’