Hypnosis
alters the brain:
8 men see
color where none exists
People have been
hypnotized to see color where only shades of grey exist,
and to see grey when actually looking at bright colourful
rectangles, from a tightly controlled scientific
experiment done at a Harvard University medical facility.
Researchers hypnotized eight people as they lay in a
scanner that recorded activity in their brains. These
subjects then tried to drain bright color from pictures,
or see color where none exist. They also attempted to do
the same thing when not hypnotized. The records of
cerebral activity clearly show that hypnosis did change
the state of the brain. "Hypnosis has a contentious
history," notes Stephen Kosslyn, professor of psychology
at Harvard and leader of the study. "Some insist it's a
state of mind that differs from normal states and
involves unique consequences; others say it's nothing
more than state-show gimmickry." When hypnotized, some
people see only shades of grey in this pattern of
brightly-colored rectangles. Such a result shows that a
state of hypnosis can change the state of the brain. eg.
, if you give some men an 1kg weight and ask them to hold
it at arm's length for as long as they can, they will be
able to do it for about 4 minutes. But if you hypnotize
them, they will hold it out for 15 minutes. That result
favors the idea that hypnotism creates an amazing unique
state of mind.
How the brain
can change.
Hypnotism is
controversial among scientists, Kosslyn and colleagues
had great difficulty in getting their research published.
2 of the world's largest scientific journals would not
publish the results. Both Kosslyn and Thompson emphasize
that the experiment worked only on "highly hypnotizable"
subjects, a category that includes only about 10 percent
of all people. "We tested 125 persons and for those who
scored lowest in hypnotizability, the results were too
low," Kosslyn says. "They couldn't do the
task."
The highly
hypnotizables slid horizontally into a positron emission
tomography (PET) scanner at Massachusetts General
Hospital, a Harvard teaching hospital in Boston. They
inhaled a short-lived, slightly radioactive type of
oxygen. The oxygen traces blood flow and makes visible
the most active parts of the brain when a subject is
hypnotized and not hypnotized.
It took between two
and ten minutes to hypnotize the people while they lay in
the scanner. A computer screen overhead then presented
them with a pattern of yellow, red, blue, and green
rectangles, similar to a painting by the Dutch artist
Piet Mondrian. They tried to "drain" the color from what
they saw on the screen while the PET scanner recorded
their brain activity. Under the same conditions, they saw
the rectangles in various shades of gray and had to color
them with their minds.
When not under
hypnosis, people asked to perceive color – whether
they actually saw color or not – showed activity on
only the right side of their brains. (The brain is split
into right and left hemispheres by a furrow filled with
nerve fibers that connect the two halves.) When told to
see gray, whether looking at color or gray, again changes
in activity occurred on the right side only.
That result was
expected on the basis of previous research. However,
under hypnotism the researchers found what Kosslyn calls
"a curious tweak." Both the left and right hemispheres
responded. In other words, the right side of the brain
alone responded to what the subjects saw when they were
not hypnotized, but both sides responded under
hypnosis.
"The left hemisphere
color area registered what people were told to see only
when they were hypnotized. The right hemisphere
registered what people were told to see
[independently of what they actually saw] whether
or not they were hypnotized," Kosslyn explains. "If you
ask people [who are not hypnotized] to visualize
color in a gray pattern, or vice versa, only the right
hemisphere is activated during the task. Thus, our
findings in the left hemisphere could not have been
produced by mental imagery alone.
"What we have shown
for the first time," Kosslyn concludes, "is that hypnosis
changes conscious experience in a way not possible when
we are not under hypnosis."
How hypnosis
works
Why the hemispheric
differences? Kosslyn and his colleagues think that the
right hemisphere is more sensitive to goals and
expectations. This part of the brain finds it easier to
reinterpret sensory experience to match the images a
person wants to perceive – to see color where none
exists, or to color a gray palette. This idea fits with
the fact that, in most people, the left side deals more
with logic and reason, so may require an extra boost from
hypnosis to disassociate itself from the senses, i.e., to
change what is actually seen.
Such disassociation of
senses, Kosslyn and Thompson speculate, may account for
the success of hypnosis in reducing pain and anxiety,
combating insomnia, and helping some people to quit
smoking. Pain, anxiety, insomnia, and smoking, might be
reduced by the same type of brain activity that allows
some people to drain color from brilliantly hued
rectangles.
Highly hypnotizables
apparently would be better at this than most people or
those who show the lowest levels of submission. Thompson
is studying the brain differences between high and low
hypnotizables. So far, he has found that the middle-part
of a brain area called the cingulate gyrus shows more
activity in the highs than lows. This area deals with
attention and emotion.
Does changing a brain
by hypnosis mean hypnotizables can gain more control over
what are normally involuntary functions of the brain
– responses to stress, regulation of hormones,
control of the immune system, for instance? Maybe. David
Spiegel of Stanford University School of Medicine, who
collaborated on the color experiments, is interested in
the possibility of bolstering the body's defenses against
disease by psychological means that might include
hypnosis. Evidence exists that strengthening these
defenses may reduce the rate of growth of cancer
tumor.
At this point,
anything beyond changing color perception is pure
speculation, Kosslyn and Thompson insist. However,
Kosslyn refers to their study as "the thin edge of a
wedge that shows that conscious experience can be changed
in a willfully directed way by hypnosis."
