A closer look: the ability to be
hypnotized seems to be a distinct trait with varied degrees of
suggestibility across the population. Photograph: Ebby May/Getty Images
Hypnosis is the eccentric uncle of cognitive science. It was
once part of the mainstream – studied by scientists and clinicians alike
in its 1960s heyday – but it slowly fell into disrepute as it was
picked up and popularized by tacky stage hypnotists and quack
practitioners in the following decades.
In recent years, hypnosis has seen something of a rebirth, and neuroscience
studies using the technique are now regularly published in some of the
most respected scientific journals. Curiously, though, it hasn't shaken
off the stigma entirely. While writing this article I contacted several
researchers who have published neuroscience studies using hypnosis, and
not one replied. The reticence is understandable. Like the study of
consciousness 20 years ago, hypnosis is still considered by some to be a
"career-limiting move". Consequently, scientists make sure they stick
to the most conservative and orthodox form of research – academic
journals, occasional conference presentations, and definitely nothing
that hints of hype, or indeed, public exposure.
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The lack of wider discussion is a pity, as hypnosis – or rather suggestibility – is a remarkable aspect of human psychology.
The ability to be hypnotized seems to be a distinct trait that is
distributed among the population, like height or shoe size, in a "bell
curve" or normal distribution: a minority of people cannot engage with
any suggestions, a minority can engage with almost all, and most people
can achieve a few.
The key word here is "engage", as, contrary to
popular belief, hypnosis cannot be used to make people do something
against their will, even though the effects seem to happen
involuntarily. If this seems paradoxical, a good analogy is watching a
movie: you don't decide to react emotionally to the on-screen
story, but you can choose to turn away or disengage at any time. In
other words, the effects of the film, just like hypnosis, require your
active participation.
The most difficult suggestions to achieve are those which affect the fundamentals of the mind, such as memory
and perception, meaning that while highly hypnotisable people can
experience temporary hallucinations and amnesia after suitable
suggestions, low-hypnotisable people may only be able to experience
temporary changes in their volition or movements – such as an arm
feeling heavier than usual, perhaps.
It seems, however, that there
is very little that can be done to make you more or less hypnotisable –
the hypnotisability trait is the primary factor in how successfully you
can experience the effects. We know that there is a genetic component
to this trait and that several studies have indicated that highly
hypnotisable people show structural and functional differences in the
brain when compared to low-hypnotisables, but the question of why we
have a varying ability to have our reality changed by suggestions
remains a mystery.
Due to their ability to have their mental
processes temporarily altered in ways previously not thought possible,
highly hypnotisable people have become key in scientific studies. Amir
Raz and colleagues at McGill University in Montreal reported that it was
possible to "switch off" automatic word reading and abolish the Stroop effect
– a psychological phenomenon that demonstrates a conflict between
meanings, such as where we are much slower to identify the ink colour of
a word when the word itself describes a different hue. Furthermore,
when this experiment was run in a brain scanner, participants showed
much lower activation in both the anterior cingulate cortex, an area
known to be particularly involved in resolving conflict between
competing demands, and the visual cortex, which is crucial for
recognising words. Although this may seem like a technicality, to the
scientific world it was a strikingly persuasive demonstration that
hypnosis could apparently disassemble an automatic and well-established
psychological effect in a manner consistent with the brain processes
that support it.
Neuro imaging has also proved key in answering the
question of whether hypnotized people are pretending to experience the
effects. When people are asked to fake hypnosis, to the point where
observers cannot tell the difference between them and the genuinely
hypnotized people, the two groups are clearly distinguishable by their
brain activity.
Taking the science one step further, researchers from the Macquarie Centre for Cognitive Science
in Sydney have published a series of studies in which they have used
hypnosis to temporarily simulate genuine conditions where patients may
hold false beliefs or lose awareness of a problem after brain injury.
One such condition, called somatoparaphrenia, can occur after
right-sided brain injury and can result in the patient denying ownership
of a limb. Literally, the patient believes that their arm is not
theirs, has been replaced, or belongs to someone else – something which
both challenges our intuitive ideas about how we perceive our body and
can pose a practical problem for post-injury rehabilitation. In highly
hypnotizeable volunteers, the Macquarie team momentarily instilled a
similar feeling of limb alienation to examine whether healthy people
could rationalize such a counter intuitive idea, finding that
participants remained consistent in their explanations even when
challenged with visual evidence.
A special issue of the respected journal Cortex
will shortly be dedicated to the neuropsychology of hypnosis,
additionally pointing to the growing momentum of the scientific revival.
The wider public, however, still base their knowledge on the watches
and weight-loss stereotype, meaning it is likely to be a while before
neuroscientists feel comfortable about breaking their self-imposed
silence
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