Robert Didden is Professor of Intellectual Disabilities, Learning and Behaviour at the Behavioral Science Institute and School of Education of the Radboud University Nijmegen, The Netherlands. He is a psychologist at Trajectum, a center for the treatment of clients with mild to borderline intellectual disabilities and behavioral and psychiatric disorders. Professor Didden is an associate editor for Review Journal of Autism and Developmental Disorders and Journal of Developmental and Physical Disabilities.