[Art_beyond_sight_theory_and_research] How Do Blind People Picture Reality?
fnugg at online.no
fnugg at online.no
Fri Oct 5 11:41:42 UTC 2012
How Do Blind People Picture Reality?
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
--- 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.
"There's plenty of imagery that goes on all the time in blind people,"
he told Life's Little Mysteries. "It just isn't visual."
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 <http://www.lifeslittlemysteries.com/2099-blind-people.html> work
around the lack of visual information, and find other ways to achieve
the same, vitally important result: a detailed 3D map of space.
The brain region neuroscientists normally think of as the "visual"
cortex, rather than being left to languish, plays a key role in the
blind's mental mapping process.
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."
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