Hypnosis Found to Affect Brain Waves : Scientist Measures a ‘Believable Change’ in Electrical Activity

STANFORD — Hypnosis causes a specific change in the electrical activity of the brain, a Stanford University Medical Center psychiatrist said.

“Our research shows a believable difference in brain waves of hypnotized and normally conscious people,” said Dr. David Spiegel, associate professor of psychiatry and behavioral sciences. “The study provides a neurological test, which distinguishes between people with high and low hypnotizability.”

The studies, reported in the August issue of the Journal of Abnormal Psychology, show that hypnotized people can tune out what is before their eyes and instead focus on internally generated images.

“The findings are a step toward understanding how people manage access to consciousness, how they control their response to pain or to unwanted ideas, the mechanism of mind over matter.”

In the experiments, volunteer students watched colored patterns that were flashed on a television screen. Such visual displays evoke certain changes in brain waves, which Spiegel measured with an electroencephalogram, a recording of the peaks and troughs of electrical activity in the brain.

Spiegel found that hypnosis alters a particular peak in the brain waves. This peak was smaller in hypnotized subjects who were told to visualize a cardboard box that blocked their view of the colors on the screen. No change in the peak was found in students who were not hypnotized.