[Nfbf-l] How do blind people picture reality?

[Alan Dicey]

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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