1. G. Allen, San Diego State University-University of California, San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA 92120, USA, and Laboratory for the Neuroscience of Autism, Children's Hospital Research Center, La Jolla, CA 92037, USA.
2. R. B. Buxton and E. C. Wong, Department of Radiology, School of Medicine, University of California, San Diego, CA 92103, USA.
3. E. Courchesne, Department of Neurosciences, School of Medicine, University of California, San Diego, CA 92093, USA, and Laboratory for the Neuroscience of Autism, Children's Hospital Research Center, La Jolla, CA 92037, USA.