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Hypnosis found to alter the brain: Subjects see color where none exists

7 min read

People have been hypnotized to see color where only shades of gray exist, and to see gray when actually looking at brightly colored rectangles.

That result wouldn’t be so surprising at a carnival or stage show, but it comes from a tightly controlled scientific experiment done at a Harvard University medical facility.

Researchers separately hypnotized eight people as they lay in a scanning machine that recorded activity in their brains. These subjects then tried to drain bright color from pictures, or see color where none existed. They also attempted to do the same thing when not hypnotized. The records of cerebral activity clearly show that hypnosis can 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.”

Color test COLOR ME HYNOTIZED: Under hypnosis, some people see only shades of gray in this pattern of brightly-colored rectangles. Such a result shows that hypnosis can change the state of the brain. As an example, if you give some men a brick 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 five minutes. But if you hypnotize them, they will hold the brick out for 15-20 minutes. That result favors the idea that hypnotism creates a unique state of mind.

However, if you tell males that some females who were just tested held the brick out for 20 minutes, they, too, will hold it for that long without being hypnotized. That result favors a suggestibility, or role-playing explanation.

“It all comes down to the question of whether the brain is doing something different,” Kossyln says. The answer apparently is yes, at least in the case of color perception.

How the brain changes

To show how controversial hypnotism is among scientists, Kosslyn and colleagues had great difficulty in getting their research published. Two of the world’s largest scientific journals wouldn’t publish the results.

“One of them asked for three separate revisions,” notes William Thompson, a research assistant in Harvard’s department of psychology. “Then they still turned down our report even after we answered all their criticisms.” After three years, their study has finally been published as the cover story in the August issue of the American Journal of Psychiatry.

Both Kosslyn and Thompson emphasize that the experiment worked only on “highly hypnotizable” people, a category that includes only about 8 percent of all people. “We pre-tested 125 subjects and for those who scored lowest in hypnotizability, the results were just garbage,” 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.”

Other researchers who participated in these experiments include Associate Professor of Radiology Nathaniel Alpert of Harvard Medical School and Maria Costantini-Ferrando of Weill Medical College, Cornell University. The research was made possible by a grant from the John D. and Catherine T. MacArthur Foundation.