1. Center for Autism Research The Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
2. Psychology Department University of Pennsylvania Philadelphia Pennsylvania USA
3. Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy University of Gothenburg Gothenburg Sweden
4. Department of Pediatrics, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
5. Department of Psychiatry, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
6. Department of Educational Psychology Baylor University Waco Texas USA