What happens in the brain during hypnosis?
Answered by Ellen Stockstill and Discovery Channel
  • Ellen Stockstill

    Ellen Stockstill

  • Discovery Channel

    Discovery Channel

  1. "You're getting very sleepy …"  Most hypnotists from the movies begin their sessions this way, dangling a pocket watch in front of their patients' faces.  In reality, however, hypnosis is not sleep.  When a person is hypnotized, he or she is not asleep but is in a trance state distinguished by suggestibility (the willingness to perform a task suggested by the hypnotist), relaxation and heightened imagination [source: Harris].  Instead of thinking about it as sleep, we might describe hypnosis as a daydream, of sorts.  In this trance-like state, a person will shut out distractions and focus on an imaginary situation that can cause real emotions and reactions.  Hypnotists, then, do not put people to sleep but focus their attention on the imaginary.

    While different theories exist about how hypnosis works, most think that hypnotism gains access to a person's subconscious.  During the focusing exercises of hypnosis, a person's conscious mind is quieted or relaxed.  As the subconscious mind takes over, a person becomes more open to accepting suggestions that the conscious mind might normally oppose (this is when stage hypnotists start to have fun). 

    As the answer from the Discovery Channel states, researchers have found that people under hypnosis experience a change in brain waves as well as an increase in activity in the creative side of the brain.  Some people, it turns out, are also better candidates for hypnosis than others.  Approximately 15 percent of people are highly susceptible to hypnosis, 10 percent are extremely difficult to hypnotize, and everyone else is somewhere in the middle [source: Geddes].  If you're a person who "gets lost" in movies or books or who tends to use the creative side of your brain more anyway, you might be a more "hypnotizable" person.  One study at the University of Virginia in Charlottesville suggests a more physical difference between those who fall under the spell and those who don't:  People more susceptible to hypnosis have larger rostrums than people unsusceptible to it.  The rostrum is a part of the brain that helps people focus, and since hypnotists lead their patients in focusing exercises in order to relax their conscious minds, it seems to make sense that this particular part of the brain would be larger in people who succumb easily to hypnosis [source: Jones].

    (Chip Simons/Getty Images)

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  2. Researchers have investigated what happens in the brain during hypnosis by measuring its electrical activity. Using electroencephalographs (EEGs), they've discovered that lower frequency waves -- which are tied to dreaming and sleeping -- are more prevalent than higher-frequency waves, which are tied to alertness [source: Harris]. This finding is associated with the relaxed state of those under hypnosis; the subconscious mind takes hold, leaving the subject highly suggestible. There are hemispheric differences as well: The left side of the brain, which is associated with logic and reason, records less activity than the right side of the brain, which is associated with creativity and emotion.

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