Tactile Vision

Tactile Vision Experiments

In 1969, “Nature”, Europe's premier science journal, published a short article that had a distinctly sci-fi feel about it. Its lead author, Paul Bach-y-Rita, was both a basic scientist and a rehabilitation physician – a rare combination. The described a device that enabled people who had been blind from birth to see. All had damaged retinas and had been considered completely untreatable.

The “Nature” article was reported in “The New York Times”, “Newsweek”, and “Life”, but perhaps because the claim seemed so implausible, the device and its inventor soon slipped into relative obscurity.

Accompanying the article was a picture of a bizarre-looking machine – a large old dentist's chair with a vibrating back, a tangle of wires, and bulky computers. The whole contraption, made of castaway parts combined with 1960s electronics, weighed four hundred pounds.

A congenitally blind person – someone who had never had any experience of sight – sat in the chaire, behind a large camera the size of those used in television studios at the time. He “scanned” a scene in front of him by turning hand cranks to move the camera, which sent electrical signals of the image to a computer that processed them. Then the electrical signals were conveyed to four hundred vibrating stimulators, arranged in rows on a metal plate attached to the inside of the chair back, so the stimulators rested against the blind subject's skin. The stimulators functioned like pixels vibrating for the dark part of a scene and holding still for the brighter shades.

The power of positive thinking finally gains scientific credibility. Mind-bending, miracle-making, reality-busting stuff... Straddles the gap between science and self-help... Illustration by Elena.

This “tactile-vision device,” as it was called, enabled blinded subjects to read, make out faces and shadows, and distinguish which objects were closer and which father away. It allowed them to discover perspective and observe how objects seem to change shape depending upon the angle from which they were viewed. The six subjects of the experiment learned to recognize such objects as a telephone, even when it was partially obscured by a vase. This being the 1960s, they even learned to recognize a picture of the anorexic supermodel Twiggy.

Everyone who used the relatively clunky tactile-vision device had a remarkable perceptual experience, as they wen from having tactile sensations to “seeing” people and objects.

With a little practice, the blind subjects began to experience the space in from of them as three-dimensional, even though the information entered from the two-dimensional array on their backs. If someone threw a ball toward the camera, the subject would automatically jump back to duck it. If the plate of vibrating stimulators was moved from their backs to their abdomens, subjects still accurately perceived the scene as happening in front of the camera. It tickled near the stimulators, they didn't confuse the tickle with a visual stimulus. Their mental perceptual experience took place not on the skin surface but in the world. And their perceptions were complex. With practice, subjects could move the camera around ans say things like “That's Betty; she is wearing her hair down today and does not have her glasses on; her mouth is open, and she is moving her right hand from her left side to the back of her head.”

True, the resolution was often poor, but as Bach-y-Rita would explain, vision doesn't have to be perfect to be vision. “When we walk down a foggy street and see the outline of a buildings,” he would ask, “are we seeing it any less for the lack of resolution? When we see something in black and white, are we not seeing it for lack of color?”

(The Brain that Changes Itself, Stories of Personal Triumph from the Frontiers of Brain Science), by Norman Doidge, M.D.)

“When we walk down a foggy street and see the outline of a buildings, are we seeing it any less for the lack of resolution?". Illustration by Elena.