After his stroke, Mr. P still had outstanding memory and intelligence. He could still read and talk, and mixed well with the other patients on his ward. His vision was in most respects normal---with one notable exception: He couldn't recognize the faces of people or animals. As he put it himself, "I can see the eyes, nose, and mouth quite clearly, but they just don't add up. They all seem chalked in, like on a blackboard ... I have to tell by the clothes or by the voice whether it is a man or a woman ...The hair may help a lot, or if there is a mustache ... ." Even his own face, seen in a mirror, looked to him strange and unfamiliar. Mr. P had lost a critical aspect of his visual intelligence.
We have long known about IQ and rational intelligence. And, due in part to recent advances in neuroscience and psychology, we have begun to appreciate the importance of emotional intelligence. But we are largely ignorant that there is even such a thing as visual intelligence---that is, until it is severely impaired, as in the case of Mr. P, by a stroke or other insult to visual cortex. The culprit in our ignorance is visual intelligence itself. Vision is normally so swift and sure, so dependable and informative, and apparently so effortless that we naturally assume that it is, indeed, effortless. But the swift ease of vision, like the graceful ease of an Olympic ice skater, is deceptive. Behind the graceful ease of the skater are years of rigorous training, and behind the swift ease of vision is an intelligence so great that it occupies nearly half of the brain's cortex. Our visual intelligence richly interacts with, and in many cases precedes and drives, our rational and emotional intelligence. To understand visual intelligence is to understand, in large part, who we are.
It is also to understand much about our highly visual culture in which, as the saying goes, image is everything. Consider, for instance, our entertainment. Visual effects lure us into theaters, and propel films like Star Wars and Jurassic Park to record sales. Music videos usher us before surreal visual worlds, and spawn TV stations like MTV and VH-1. Video games swallow kids (and adults) for hours on end, and swell the bottom lines of companies like Sega and Nintendo. Virtual reality, popularized in movies like Disclosure and Lawnmower Man, can immerse us in visual worlds of unprecedented realism, and promises to transform not only entertainment but also architecture, education, manufacturing, and medicine. As a culture we vote with our time and wallets and, in the case of entertainment, our vote is clear. Just as we enjoy rich literature that stimulates our rational intelligence, or a moving story that engages our emotional intelligence, so we also seek out and enjoy new media that challenge our visual intelligence.
Or consider marketing and advertisement, which daily manipulate our buying habits with sophisticated images. Corporations spend millions each year on billboards, packaging, magazine ads, and television commercials. Their images can so powerfully influence our behavior that they sometimes generate controversy---witness the uproar over Joe Camel. If you're out to sell something, understanding visual intelligence is, without question, critical to the design of effective visual marketing. And if you're out to buy something, understanding visual intelligence can help clue you in to what is being done to you as a consumer, and how it's being done.
Perhaps the most surprising insight that has emerged from vision research is this: Vision is not merely a matter of passive perception, it is an intelligent process of active construction. What you see is, invariably, what your visual intelligence constructs. Just as scientists intelligently construct useful theories based on experimental evidence, so vision intelligently constructs useful visual worlds based on images at the eyes. The main difference is that the constructions of scientists are done consciously, but those of vision are done, for the most part, unconsciously.
The constructive power of visual intelligence has long fascinated vision researchers. How can vision conjure up the endless panoply of colors and shapes and motions that we see about us in the ``real'' world? How can it morph a mass of metal into a murdering maniac in the world of Terminator 2? How can it stretch before us a world in three dimensions when we watch, with special glasses, a 3D movie like Dial M for Murder? How can it "boldly go where no man has gone before", not just through the "strange new worlds" of Star Trek but through the stranger new worlds revealed by the cameras of the Hubble telescope and of probes like Voyager and Pioneer, worlds for which the eye has not obviously been adapted?
Vision has divulged many of its secrets to physicists, neurobiologists, perceptual psychologists, and researchers in computer vision. But, many interesting secrets are yet to be unveiled. These secrets, both revealed and unrevealed, of your visual intelligence are sure to pique in you the same admiration and curiosity that animate vision researchers.
For some, science is like a "reaper binder" that methodically mows down wheat: Science methodically mows down unanswered questions and leaves ever less room for wonder. But our exploration of visual intelligence will suggest that science is more like an island: "The larger the island of knowledge, the longer the shoreline of wonder." For each question we answer ten new ones arise, and for each new probe at nature entire vistas arise.
- Donald D. Hoffman