Book Review: "Believing is Seeing"

[Timothy Gangwer]

Visual Intelligence: How We Create What We See. Donald D. Hoffman. 294 pp. W. W. Norton & Company, 1998.

Those of us not expert in the study of vision might assume the process of seeing to be complicated but straightforward. Wrong. Complicated, yes; straightforward, never. In this book on vision, Donald Hoffman lets the reader in on the "secrets" of what he calls our visual intelligence. He theorizes that what we see is constructed by the brain as it builds an image from information entered through the eye and located on the retina. This built image is but one of many possible images. Definitely this is not straightforward. The constructive nature of vision captivates the reader because the notion seems to defy common sense. We are moved to ask why and how. Hoffman says, "Without exception, everything you see you construct: color, shading, texture, motion, shape, visual objects and entire visual scenes." He goes on to explain vision in terms of "phenomenal" and "relational." By the last chapter, an interesting leap into virtual reality and the "icon metaphor," he has succeeded in teaching us the rules of visual processing. The text is supplemented throughout with illustrated figures (many of them familiar to students of vision) and photographs that ably allow us to see what is being described.

Many chapters begin with engaging vignettes and case studies of people who have suffered brain injuries through stroke or accident, such as the woman who could not see objects in motion. This approach will remind some of books by Sacks and Ramachandran. These fairly rare consequences of misfortune are inestimable as teaching opportunities, for in showing what can go wrong with vision, we can learn how the visual system works. A condition called "Williams syndrome" affects one in 20,000 people. People so afflicted cannot assemble parts in a picture—if asked to draw an elephant, they will render its parts in erroneous spatial locations. Although the book focuses on vision, Hoffman includes a chapter to help us understand that every sensation—sight, smell, touch, hearing—is constructed. Perhaps a future book will explicate the constructive nature of all the other senses.

Missing is any discussion of the cultural influences on perception and vision. For instance, there is no mention of the "carpentered world" effect, in which people who live in environments of angles and geometric designs are more susceptible to certain illusions that people from landscapes with round houses and a paucity of straight lines and angles have little difficulty with, although they may be more likely to be fooled by others. Also, it would have been helpful had the author listed all 35 purported innate rules for visually processing shapes, color and motion.

Visual Intelligence is approachable to learned and lay readers alike and will appeal to anyone enticed by the notion that not just our eyes but also our brains determine what we see. It is written in an easygoing, conversational style with references about our reactions to such everyday things as movies, barber shop poles and traffic lights.—Evangeline A. Wheeler, Psychology, Towson University

- Evangeline Wheeler
American Scientist Online