CHARLES G. COSTELLO, PhD, is Emeritus Professor of Psychology, University of Calgary. Dr. Costello attended Manchester University, Durham University, and London University, from which he received his doctorate in psychology in 1960. In 1989, he was awarded The Psychologists' Association of Alberta President's Award for Exceptional Contributions to the Discipline of Psychology in Alberta. A prolific writer, he is the author of more than 90 published articles on a wide range of topics in psychology. His other books include Symptoms of Psychopathology, Symptoms of Depression, Symptoms of Schizophrenia, Psychology for Psychiatrists, and N=1: Experimental Investigation of the Individual Case.