Neuroimaging studies are helping hypnosis shed its
'occult' connotations by finding that its effects on
the brain are real:
By Lea Winerman
Mention hypnosis, and for many people the image that
comes to mind is a charlatan with a watch swinging
back and forth, seducing otherwise sensible audiences
into barking like dogs or clucking like chickens.
Today, though, psychologists and others are using
hypnosis to help patients stop smoking, lose weight or
control pain. But despite this newfound respect for
the method, scientists still aren't sure precisely how
hypnosis–whether on stage or in a clinician's
For years, they've been trying to determine whether
hypnotized people actually feel and see things
differently than the nonhypnotized or whether the
hypnotized give in to some combination of
concentration and social pressure to follow
Now, in the past decade or so and with the advent of
neuroimaging technology like functional magnetic
resonance imaging (fMRI), researchers have begun to
get some answers.
Recent studies have found that when hypnotized people
act on hypnotists' suggestions, their brains really do
process information differently. When they're told to
see colors, for example, the color-processing parts of
their brains light up–despite the absence of any real
color in front of them.
"This is an exciting time for us," says Columbia
University psychologist and hypnosis researcher Amir
Raz, PhD. "Neuroimaging technology allows us to really
look at what's going on in the brain during hypnotic
Now, Raz and others are beginning to branch out, to
try to figure out why hypnosis works and why some
people are more hypnotizable than others. They hope
that their research will lead to not only a better
understanding of a previously mysterious phenomenon,
but also to more effective hypnosis treatments.
In one recent study, Raz found that he could use
hypnosis to negate the Stroop effect, a task that
demonstrates how attention processes can interfere
with each other. In the task, participants view the
names of colors printed in different colors of ink–for
example, the word "red" printed in blue ink–and try to
say the name of the ink color while ignoring the
words. But people who are literate read the words
automatically and so find the task difficult. They
often respond slowly and mistakenly read the words
rather than identify the ink color.
In a recent study, published in the Proceedings of the
National Academy of Sciences (Vol. 102, No. 28, pages
9,978–9,983), Raz and his colleagues tested eight
highly hypnotizable people and eight who weren't
hypnotizable at all. The researchers performed a
hypnotic induction, using methods such as guided
imagery and visualization. Then, they told the
participants that they would later see "meaningless
symbols" printed in different colors of ink, and that
when they did, they should press a computer key
corresponding to the correct ink color.
Next, the researchers brought the participants out of
hypnosis, put them in an fMRI machine and showed them
the Stroop stimuli. But the hypnotizable patients who
had been told that they'd see gibberish seemed, in
fact, to see gibberish: They performed the task almost
10 percent faster than the nonhypnotized participants,
and made fewer mistakes.
"It appears that these people were not playing games,
and they were not acting," says Raz. "They were
genuinely not reading the words."
The fMRI results were also striking. The hypnotizable
participants showed less activity in an area called
the anterior cingulate cortex, which is active when
people are trying to resolve conflicting information
from different sources–information like conflicting
word names and colors.
Studies that have examined other types of hypnotic
suggestions have found similar evidence. For example,
Harvard psychologist Stephen Kosslyn, PhD, found that
when he told hypnotized subjects that they would see
gray-scale printed, Mondrian-like patterns in color,
the participants showed activation in the same area of
the brain–the right fusiform gyrus–as when they viewed
actual color prints, according to a study published in
the American Journal of Psychiatry (Vol. 157, No. 8,
pages 1,279–1,284). That area didn't light up,
however, when the subjects weren't hypnotized and
Kosslyn simply suggested that they visualize the
drawings in color.
Another experiment found that hypnotically induced
pain activated the same brain areas as "real" pain. In
this 2004 study, published in Neuroimage (Vol. 23, No.
1, pages 392–401), University College London
psychologist David Oakley, PhD, and his colleagues
told eight highly hypnotizable participants that they
would feel heat-related pain. They found that the same
pain-processing areas of the brain–in the thalamus,
anterior cingulate cortex and other areas–were active
in those subjects as in subjects who actually touched
a 120-degree metal probe. Subjects who simply imagined
the pain, meanwhile, didn't show the same active brain
The accumulating evidence suggests that people respond
to hypnotic suggestion by actually "feeling" or
"seeing" the suggested stimulus, be it pain or color.
The question that researchers have yet to answer,
Oakley says, is how those changes come about.
Scientists are still split on the issue: Some believe
that hypnosis puts people into a trance state in which
the brain behaves measurably differently than it does
in other states. Others, meanwhile, believe that
hypnosis is simply an intense form of concentration or
So far, neuroimaging studies haven't been able to
distinguish between the two. To do so, a researcher
would need to find a difference in brain activity
between a hypnotized and a nonhypnotized
person–specifically, a difference unrelated to the
effects of any particular suggestion such as seeing
color, says University of Plymouth psychology
professor Irving Kirsch, PhD.
"Nobody has yet disentangled the effect of suggestion
from the effect of hypnotic induction," Kirsch says.
"That's probably the next step."
In fact, he and Raz have begun to address the question
with behavioral measures. In one study, published in
February in Psychological Science (Vol. 17, No. 2),
they repeated the Stroop experiment but this time
included a condition in which they simply told the
highly hypnotizable participants, who were not
hypnotized at that time, that they would see gibberish
rather than words.
The researchers found that, for these highly
suggestible people, the suggestion alone was enough to
improve performance on the task.
"We now have evidence showing that highly hypnotizable
people do not need to be hypnotized in order to
benefit from suggestion," Raz says. That indicates
that hypnosis may be a normal state of consciousness
rather than an altered state–and that some people who
are particularly good at experiencing imaginative
suggestions are the ones who can be hypnotized, Kirsch
Meanwhile, researchers who believe that hypnosis
alters the brain's functioning in some fundamental way
say that the new findings don't negate that
possibility. John Gruzelier, PhD, a psychologist at
Imperial College in London, acknowledges that easily
hypnotizable people are more suggestible even when not
hypnotized. However, he says, the hypnosis itself
still makes a difference.
"It's my feeling that we wouldn't bother going through
the whole rigmarole of hypnosis if it was
unnecessary," he says.
Raz and Kirsch hope that this and other work will also
begin to help explain why some people are more highly
hypnotizable than others, and will give researchers
insight into who is most likely to benefit from hypnosis.