Paul Harris is interested in the early development of cognition, emotion and imagination. After studying psychology at the University of Sussex and the University of Oxford, he taught at the University of Lancaster, the Free University of Amsterdam, and the London School of Economics. In 1980, he moved to Oxford where he became a professor of developmental psychology and fellow of St John's College.

During the 1980s, his research focused primarily on children’s understanding of mental states, including emotion. The findings were gathered together in a book published in 1989, Children and Emotion (translated into seven European languages) as well as two edited volumes (Developing Theories of Mind and Children’s Understanding of Emotion). In the 1990s, he studied the development of pretend play and imagination, culminating in a book, The Work of the Imagination, published in 2000 and an edited volume (Imagining the Impossible: Magical, Scientific and Religious thinking in Children). In 2001, he migrated to Harvard University, where he holds the Victor S. Thomas Professorship of Education

Currently, he is studying how far children rely on their own first-hand observation or, alternatively, trust what other people tell them—especially when they try to understand a domain of knowledge in which first-hand observation is difficult. His latest book, Trusting What You’re Told: How Children Learn from Others, synthesizes a broad range of findings on this topic. It has received the Eleanor Maccoby Book Award from the American Psychological Association and the Cognitive Development Society Book Award.