How Do Blind People Picture Reality?

Imagine picturing a table without constructing a visual image.

(Image credit: Public domain)

Paul Gabias has never seen a table. He was born prematurely and went blind shortly thereafter, most likely because of overexposure to oxygen in his incubator. And yet, Gabias, 60, has no trouble perceiving the table next to him. "My image of the table is exactly the same as a table," he said. "It has height, depth, width, texture; I can picture the whole thing all at once. It just has no color."

If you have trouble constructing a mental picture of a table that has no color — not even black or white — that's probably because you're blinded by your ability to see. Sighted people visualize the surrounding world by detecting borders between areas rich in different wavelengths of light, which we see as different colors. Gabias, like many blind people, builds pictures using his sense of touch, and by listening to the echoes of clicks of his tongue and taps of his cane as these sounds bounce off objects in his surroundings, a technique called echolocation.

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As well as being blind himself, Gabias is an associate professor of psychology at the University of British Columbia who conducts research on perceptual and cognitive aspects of blindness. His personal and professional experience leads him to believe that the brains of blind people work around the lack of visual information, and find other ways to achieve the same, vitally important result: a detailed 3D map of space.

In sighted people, visual information first goes to the visual cortex, which is located in the occipital lobe at the back of the brain. From there, it goes to the parietal lobe, sometimes referred to as the "where system" because it generates awareness of a sensed object's location. Next, the information is routed to the temporal lobe, also known as the "what system" because it identifies the object.

Evidence from recent brain-imaging experiments indicates that blind people's brains harness this same neural circuitry. "When blind people read Braille using touch, the sensory data is being sent to and processed in the visual cortex," said Morton Heller, a psychologist who studies spatial cognition and blindness at Eastern Illinois University. "Using touch, they get a sense of space" — and the relative locations of the raised dots that form Braille letters — "that's not visual, it's just spatial."

For blind people who are adept at echolocation, sound information routes through the visual cortex as well. Their brains use echoes to generate spatial maps, which are sometimes so detailed that they enable mountain biking, playing basketball and safely exploring new environments. In fact, last year, Canadian researchers discovered that even when blind echolocation experts listened to audio recordings of their tongue clicks echoing off different objects, they could easily identify the objects that had been present at the time of the recordings. Scans with functional magnetic resonance imaging (fMRI) showed activity in areas of their brains associated with visual processing. In other words, their brain scans resembled those of a sighted person identifying an object in a photo.

Natalie Wolchover was a staff writer for Live Science from 2010 to 2012 and is currently a senior physics writer and editor for Quanta Magazine. She holds a bachelor's degree in physics from Tufts University and has studied physics at the University of California, Berkeley. Along with the staff of Quanta, Wolchover won the 2022 Pulitzer Prize for explanatory writing for her work on the building of the James Webb Space Telescope. Her work has also appeared in the The Best American Science and Nature Writing and The Best Writing on Mathematics, Nature, The New Yorker and Popular Science. She was the 2016 winner of the Evert Clark/Seth Payne Award, an annual prize for young science journalists, as well as the winner of the 2017 Science Communication Award for the American Institute of Physics.