Subject: do: Kognitywistyka  ??? 

How we distinguish a cat from a dog

January 12, 2001
Web posted at: 3:56 PM EST (2056 GMT)

WASHINGTON (Reuters) -- It might not seem like being able to tell a cat
from a dog is an important skill, but researchers said Thursday they had
found monkeys have brain cells specifically assigned to the task and
people may, too.

The team at the Massachusetts Institute of Technology found that
individual neurons in the monkeys' brains became tuned to the concept of
"cat" and others to the concept of "dog."

Writing in the journal Science, they said their study shows how the brain
categorizes things.

"One of our most fundamental behaviors is to assign meaning to what's
around us," Earl Miller, an associate professor of brain and cognitive
sciences who helped lead the study, said in a statement.

"When we enter a room, we don't spend a lot of time and effort identifying
the objects. We know immediately if something is a chair or a table, and
how to use it, even if we have never seen that particular chair or table
before."

Yet, he said, scientists know almost nothing about how the brain does
this.

Miller, a neural scientist, said he believed individual neurons would have
to be involved.

"Imagine a young child learning about a cat," he said in a telephone
interview. "You have a very long laundry list about what makes a cat. If
it has long whiskers, purrs and has fur, it must be a cat. This
information gets encoded in single neurons in the brain."

The brain has to be able to get this information and put it together
quickly.

"By encoding the information on a single cell level, the brain can
automatically and effortlessly categorize everything," Miller said.

He and colleagues showed their rhesus monkeys computer- generated images
of "generic" cats and dogs -- a house cat, a tiger and a cheetah, and a
German shepherd, a pointer and a St. Bernard.

Blended images

They blended the six images into a single image. As soon as the image was
more than half cat or dog, the monkeys, which had never seen a live
example of either type of animal, correctly categorized it 90 percent of
the time.

"It was a long, slow learning process, but they learned what makes a cat a
cat and what makes a dog a dog," Miller said.

"The monkey's individual neurons became sensitive to features that
comprise a dog or cat. With enough experience, that happens
automatically."

To follow what the neurons were doing, they stuck extremely thin wires
into the monkey's brains. Such wires are often used to monitor individual
neurons in the brains of laboratory animals.

"It's a painless procedure," Miller said. "We recorded the prefrontal
cortex, which is important to high-level cognitive function. We thought it
was a likely spot."

Because monkey's brains are so similar to the brains of humans, Miller
said he was certain the same thing happens in people -- although he said
he cannot go around sticking wires into the brains of human volunteers.

Next he wants to find other regions of the brain that are involved in this
process of categorizing. "It is certainly not the prefrontal cortex
alone," he said.
 
 

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