Mark Henderson, at the American Association for the Advancement of Science conference in Boston, reports :

Hypnosis really does turn red into white

SCIENTISTS have shown that hypnosis produces clear changes in the brain, the first conclusive proof that the practice works.

Brain scans have revealed beyond doubt that people who are hypnotised are not simply humouring their interviewers but that they see the world differently while in a trance.

The findings offer evidence that hypnosis has biological as well as psychological effects, confounding the sceptics who believe that the technique is little more than acting or role-playing. They also support the use of hypnosis as a medical tool for treating pain and other disorders.

David Spiegel, Professor of Psychiatry and Behavioural Sciences at Stanford University in California, who led the study, said that opinions on hypnosis could no longer be a question of belief.

"There is faith and belief, and then there’s science," he said. "This is scientific evidence that something unusual happens in the brain that doesn’t happen ordinarily.

In the study, details of which were presented yesterday at the American Association for the Advancement of Science conference, Professor Spiegel’s team used a scanning technique called positron emission tomography (PET) to examine the brains of eight people who had been hypnotised.

The volunteers, all of whom were highly hypnotisable, were shown a coloured grid similar to a Mondrian painting and were asked to imagine the colour draining from the picture to leave only black and white. The PET scans, which measure blood flow and activity in the brain, showed that the subjects started to see the image in black and white. Blood flow and activity were noticeably reduced in the parts of the brain that deal with the perception of colour, while the areas that process grey-scale images were stimulated.

When the experiment was reversed, with the hypnotised subjects asked to see a grey-scale grid in colour, the scientists saw similar results: the PET scans showed a clear stimulation in the colour centre of the brain, even though the image was black and white.

"Under hypnosis, believing is seeing," Professor Spiegel said. "When people believe there is colour in the picture, their brains process the colour even if it isn’t there. They are not just telling you what you want to hear: the way their brains respond to the information is actually being changed."

He added: "Hypnosis has been something like the oldest profession: everyone is interested in it but no one wants to be seen in public with it." Sceptics often contended that people who claimed to have been hypnotised were in fact acting.

That view has always been difficult to rebut, even in the face of evidence about the medical benefits of hypnosis: it is argued that such benefits as the well-documented capacity of hypnosis to relieve pain are due to the placebo effect and distraction from pain stimuli.

The new research gives the lie to that school of thought, proving that hypnosis has a clear physiological effect