People
have been hypnotized to see color where only shades of gray
exist, and to see gray when actually looking at bright
colorful 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 gray in this
pattern of brightly colored rectangles. Such a result shows
that a state of hypnosis can change the state of the brain.
e.g.. , if you give some men an 1 kg 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, 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,"
The
highly hypnotic subjects slid horizontally into a
positron emission tomography (PET) scanner. 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 that 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 . 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, is that hypnosis changes
conscious experience in a way not possible when we are not
under hypnosis.
How
hypnosis works:
Why the
hemispheric differences? 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, 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
hypnotic subjects apparently would be better at this than
most people or those who show the lowest levels of
submission, after studying the brain differences between
high and low hypnotic subjects. So far, we 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 hypnotic subjects 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. However, this study is "the thin edge of a
wedge that shows that conscious experience can be changed in
a willfully directed way by hypnosis."