[Nfbf-l] How do blind people picture reality?
Alan Dicey
adicey at bellsouth.net
Tue Oct 9 04:56:38 UTC 2012
How do blind people picture reality?
By Natalie Wolchover, Life's Little Mysteries Staff Writer.
Date: 04 October 2012.
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.
"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 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. [Do Color blind People Dream In Color?]
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.
Clearly, detecting visual contrasts is only one method of many for
perceiving reality. But when trying to imagine a world perceived using
hearing or touch, one tends to automatically picture echoes and textures
generating a visual image built out of contrasts between light and dark.
Gabias cannot conceive of light and dark. So what, exactly, are his mental
images like?
"I just picture tables. We have no idea what our brain is doing. We just
perceive - that's the wonderful thing about it. This is all
'psychologization' that has made it complicated to explain, but simple to
do. You don't know how you perceive. You just do it," he said.
"If you know that blind people know where to put their plates on their
table, and you know that blind people deal with tables in the exactly the
same way you do, then you presume that they imagine them in the same way
you do. You have got to presume that what's inside their head is like
yours."
Source URL:
http://www.livescience.com/23709-blind-people-picture-reality.html
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