Biologist Robert Sapolsky. He's one of the first researchers to chart the effects of chronic stress on the brain in the animal kingdom and in humans. He adds a touch of humor to his findings, as well. His new book is called "Why Zebras Don't Get Ulcers: An Updated Guide to Stress, Stress-Related Diseases, and Coping." (W.H. Freeman and Co.) It's a revised version of his 1994 publication.