Vision Without Recognition

Kevin Chappell, a graduate student and musician, was riding his bike one day when he was hit by a car. His recovery was almost complete except for one problem. He was no longer able to recognize objects. His vision was excellent. He could identify shapes and colors and movement. He just didn’t know what he was looking at. He can identify objects using other senses. Given a bar of soap, he first thought it was a scented candle, but then he correctly guessed what it was. He can identify trees because he sees an expanse of green and blocks of brown when he is outside.

He has not forgotten what objects look like. When asked to draw a scrub brush, he produced a three-dimensional drawing similar to the one below. But some time later, when shown his own drawing, he was unable to identify it.

Kevin has lost the ability to read, which made completing his graduate education difficult. He persisted and got his degree. He can no longer read music, a skill he once had, but he is still a good musician.

There is just one type of visual object that Kevin Chappell can recognize well: faces.

A New Focus After Injury

Terry Sweeney was a firefighter until she sustained a head injury. Like Kevin Chappell, she almost completely recovered, but she does have one problem. She can no longer recognize people by their faces. Her vision is excellent, good enough to allow her to take up a new profession: photography.

Terry can see faces—the eyes, the nose, the mouth, and all—but these pieces do not come together to allow her that instant recognition that is commonplace for most of us. She does not even recognize herself when shown a picture without other contextual cues. Terry still recognizes people by their voices, the way they move, or the clothes they are wearing.

Understanding Agnosia: The Disconnect Between Sensing and Knowing

Both Kevin and Terry have conditions called agnosias, where damage to the brain prevents sensory information from reaching the knowledge that is needed for identification. The sense of vision is fine, and the visual knowledge that make perception of faces or objects possible is still present. Perception is simply cut off from sensation.