Book excerpt: Imagine a world in which words have colors and sounds have tastes. In his autobiography, Vladimir Nabokov described this neurological phenomenon, which helped inspire David Hockney's sets for the Metropolitan Opera. Richard Feynman experienced it while formulating the quantum theory that won him a Nobel Prize. Sometimes described as a blending of perceptions, synesthesia occurs when only one of the fives senses is aroused but two respond. Journalist Patricia Lynne Duffy draws from her own struggles and breakthroughs with synesthesia to help us better understand the condition, while describing some of the major theories surrounding it. An illuminating examination of the world of synesthetes, Blue Cats and Chartreuse Kittens is a must-read for science and health buffs, as well as for artists, writers, and creative thinkers-or anyone generally intrigued by the brain, the senses, and perception.