1. B. J. Knowlton, Department of Psychology, University of California, Los Angeles, CA 90024, USA.
2. J. A. Mangels, Rotman Research Institute, Baycrest Centre for Geriatric Care, North York, and University of Toronto, Toronto, Ontario M6A 2El, Canada.
3. L. R. Squire, Veterans Affairs Medical Center, San Diego, CA 92l6l, USA, and Departments of Psychiatry and Neurosciences, University of California San Diego School of Medicine, La Jolla, CA 92093, USA.