Martijn van Zomeren is Professor of the Political and Cultural Psychology of Social Relationships at the University of Groningen, the Netherlands. He is a world expert on the psychology of social protest. His collaborative theoretical and empirical work over the last 20 years identified core motivations for people to act for social change across diverse political and cultural contexts. Van Zomeren's broader theoretical contributions offer a bigger picture of where those core motivations come from, based in a relational-psychological theory of motivation.