What Is the Science Behind Hypnosis?

Answer by Paul King, Computational Neuroscientist

Hypnosis is a real phenomenon, and even animals can be hypnotized. But what hypnotism is, exactly, remains unclear.

In a remarkable experiment reported in the New York Times [1], subjects were given the post-hypnotic suggestion that they would see words that would appear incomprehensible as if in a foreign language. They were then put in a brain scanner and asked to perform the “Stroop task” in which one reads aloud the color of words but not the text.

Here is an example Stroop task shown in English and Dutch.

When the words are in a foreign language, the task is easy. When they are in your native language, it is almost impossible to do correctly (try it!) due to an “interference effect” that causes the meaning of the words to take priority over their visual color.

However with the post-hypnotic suggestion, subjects were able to do this task effortlessly. Not only that, but the fMRI brain scan revealed that the brain region responsible for language did not become activated. So not only did the words “seem” to the subject to be in a foreign language, the brain actually processed them as if they were. This experiment may be the first solid evidence that hypnosis is a real neurological phenomenon.

But what kind of phenomenon is it? This is where the controversy begins.

Hypnosis is generally regarded as an altered state of consciousness, a broad category that includes meditative states, the “flow” state, psychedelic drug-induced states, and psychosis. But since consciousness isn’t understood, alterations to it aren’t very well understood either.

More specifically, hypnosis is a state of extreme “suggestibility,” a phenomenon that includes the placebo effect, advertising, and religious cults, but may also include any context-specific behavior. If a stranger at a train station asks you to —> Read More