The true nature of hypnosis has eluded scientists. It's clear people can be hypnotized, but it's not clear how this happens. New research offers a clue.
By recording the eye movements of a hypnotized woman, and comparing them with those of nonhypnotized people, researchers say they have found evidence that hypnosis involves a special mental state, fundamentally different from normal consciousness.
First some basics: When under hypnosis, a person becomes more capable of hallucination and susceptible to suggestions, perhaps intended to help him or her stop craving cigarettes, say, or prompt him or her to hear music that isn't actually playing. If no suggestions are given, a hypnotized person will sit still and his or her mind will enter a calm state, like that associated with meditation. After a session ends, the person doesn't remember it, according to study researcher Sakari Kallio, an associate professor at the University of Skövde in Sweden and University of Turku in Finland.
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The debate
Some believe these things happen because of a change in brain activity that alters a person's state of consciousness. Another camp believes that under hypnosis, the brain functions just as it would at any other time while awake, and that other, normal processes — like an active imagination — are at work.
Solving this debate by measuring brain activity is dicey, since our brain's electrical activity can vary significantly from moment to moment during its normal state. But the identification of a behavior associated with an altered state of consciousness — something no one could fake — would go a long way to supporting the idea that hypnosis involves a change in consciousness.
And that's exactly what a team of researchers says they have found, by looking at the eye movements of an easily hypnotized Finnish woman.
All in the eyes
This woman, identified in the study published in the journal PLoS ONE on Oct. 24 only by her initials TS-H, is 43, an office worker, right-handed, and "as normal as can be," said Kallio, the lead study researcher. TS-H has no history of any neurological or psychiatric illnesses and a normal psychological profile, he and colleagues wrote. [10 Controversial Psychiatric Disorders]
She is, however, also unusually responsive to hypnosis. Kallio said that while TS-H was hypnotized, he could easily induce her to see or hear things that weren't present, and that she forgot the session when the hypnosis ended.
Using three different visual tests, they found that while hypnotized, her pupils became smaller and she blinked more slowly and less frequently — about 10 times less often –- than normally. When moving her gaze to a new point on a screen, her eyes "crept" along, moving in shorter jumps, when normally they would have moved swiftly. And, when watching the middle point of a field of moving bars, her eyes made fewer, smaller, slower movements back and forth.
Because people have little conscious control over these kinds of movements, it is unlikely someone could fake them, according to Kallio.
He and colleagues gave 14 nonhypnotized volunteers the same tasks, and asked the volunteers to perform them naturally, and to try to mimic hypnotized eye movements. While in some instances, such as with blinking, the nonhypnotized volunteers did well, overall, none came close to matching the hypnotized eye movements.
The results don’t come without precedence; a change in the eyes, or a unique sort of stare, has long been associated with hypnosis.
Measurements of electrical activity in TS-H's hypnotized brain taken in separate research also indicate something was going on. In three different experiments, researchers found changes they would not expect in a normal brain, according to Kallio.
In one study, the connections between the frontal area and the rest of the brain diminished dramatically, which typically happens during sleep. Then hypnosis also made her brain's right hemisphere more dominant, although this finding is difficult to interpret, Kallio told LiveScience in an email.
While a bit trickier to interpret, brain measurements further support the idea that something unique happens in TS-H's brain during hypnosis, according to Kallio.
You can follow LiveScience senior writer Wynne Parry on Twitter @Wynne_Parry. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.
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