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From the issue dated December 14, 2001
Synesthetes Show Their Colors
By LILA GUTERMAN
Some people lead much more colorful lives than the rest of
us, experiencing the worldawash in hues and tones that evade
the average person. Those extraordinary individuals, known as
synesthetes, encounter interactions among their senses daily:
They see colors when they hear musical tones, envision shapes
when they smell certain odors, or, most commonly, see colors
when they read letters or numbers.
Neuroscience has traditionally paid little attention to
synesthesia. Many people doubted that it was even a real
experience, until British researchers performed experiments in
the early 1990s that showed that synesthetes could remember
associations between colors and letters, words, or phrases far
better and longer than nonsynesthetes.
Now that synesthesia is accepted as real, some researchers
have turned to proving that it stems from a person's
perceptions of objects, says Jeffrey A. Gray, an emeritus
professor of psychology at the Institute of Psychiatry, in
London. Synesthesia could instead arise from strong memories
of associations learned in childhood-from colored alphabetic
refrigerator magnets, for instance. Or it could be metaphoric,
"like you might say that cheddar cheese is sharp," says
Vilayanur S. Ramachandran, a professor of psychology at the
University of California at San Diego. He and Edward M.
Hubbard, a graduate student, have recently proved that
synesthesia is indeed a sensory phenomenon. And they think
they know how synesthetes' brains mix up the senses.
'They're Better at It'
The researchers showed two synesthetes and 20 control subjects
a display of computer-generated 2s and 5s, rendered so that
they were mirror images of each other. Among many 5s, the
display contained 2s arranged in a simple shape, such as a
circle. The normal subjects took a long time to find the
shape, having to scan each numeral to determine if it was a 2
or a 5. But to the synesthetes, who saw the two numbers as
having distinctly different colors, the shape popped out.
"These people instantly see a red circle," says Dr.
Ramachandran. "They can't be making it up, because they're
better at it than us."
Dr. Ramachandran thinks that crosswiring in the brain causes
the colored numbers. Researchers have previously shown that
the areas of the brain that deal with colors and numbers lie
adjacent to one another. "This is too good to be a
coincidence," he says. He is now beginning brain-scanning
experiments on number-color synesthetes.
Mr. Gray has already done brain scans on another category of
synesthetes, those who see colors when they hear words. His
results align with Dr. Ramachandran's evidence showing that
synesthesia is perceptual. In yet-to-be-published work, Mr.
Gray scanned the brains of 10 synesthetes and 10 control
subjects while they listened to words and to pure tones. In
the synesthetes, listening to words caused significantly more
activity in the part of the brain that recognizes color.
His results, he says, also conform with Dr. Ramachandran's
interpretation of how the brain creates synesthetic
experiences. "Our results rather strongly suggest that there
is some form of a linkage in the brain between the language
systems ... and the color-specific region," he says.
Dr. Ramachandran says that studying synesthetic connections
between senses can help to understand how senses interact in
the normal brain. "Even in nonsynesthetic minds, the ability
to link ideas is based on these types of crosswirings.
[Synesthetes] just have more crosswiring," he says. But Mr.
Gray isn't so sure. Such crosswirings may not exist in
nonsynesthetic brains, he says. It is also possible that all
infants have such multisensory connections but that the brain
prunes them as people age, except in the case of synesthetes,
suggests Mr. Gray. If that is the case, then studying
synesthetes could shed light on the developing brain.
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Copyright 2001 by The Chronicle of Higher Education
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