Hypnosis a state of heightened suggestibility people experience imagined suggestions

as if they were real.

Franz Anton Mesmer (1734-1815)

Austrian physician who developed technique ‘animal magnetism’ (later renamed mesmerism).

Noticed patients enter trance-like state. Apparent ‘miracle cures’

1841 Scottish surgeon James Braid witnessed mesmerism /developed own

techniqueBraid held bright object in front of patients’

eyes while making verbal suggestionsRenamed it hypnosis after Hypnos,

Greek god of sleep.

Hypnotic Induction

• Process by which one person leads another into hypnosis.

• Not necessary to swing watch in front of eyes or say “you are feeling sleepy”!

•The goal >to relax subject and increase attention

•Essential feature of procedure is subject must realize they are being hypnotized

•Not possible to be hypnotized against your will

Hypnotic SusceptibilityHilgard’s Hypnosis

According to Hilgard (1977), in average testing session

• 10% of subjects will be completely nonresponsive• 10% will pass all or nearly all items • Rest will fall in between.• Susceptibility enhanced by increasing people’s

expectations (Spanos et al., 1991; Vickery & Kirsch, 1991).

Stanford Hypnotic Susceptibility Scale

Item Suggested Behaviour Criterion for Passing

Arm lowering Right arm will become heavy

Arm lowered by at least 6 inches

Moving hands apart Force is pushing hands apart

Hands are 6 or more inches apart

Mosquito hallucination

Mosquito is buzzing nearby

Any grimace or acknowledgement

Posthypnotic amnesia Will not remember suggestions

Three or fewer items recalled

Behavior under Hypnosis

• Hypnotized people are suggestible • Behavior will conform with what hypnotist tells them

Typical behaviour that can be induced include:• Acting out imaginary scenes.• Pretending to be an animal.

• Believing a limb cannot move or is insensitive to pain.• Positive and negative hallucinations – seeing things that are

not really there, or not seeing objects that really are present.

http://www.youtube.com/watch?v=8CUHSoFUHTc

• Posthypnotic suggestibility – subject given instructions under hypnosis and follows them after returning to non-hypnotized state

• Posthypnotic amnesia – subject is instructed to not remember suggested behavior after leaving hypnotic state.

Brain under hypnosis

Hypnosis and changes in perception• Does hypnosis change person’s perception during

positive and negative hallucinations?• Miller et al. (1973) tested hypothesis using

Ponzo illusion

• Via hypnotic suggestion participants told slanted

lines ‘disappeared’• Subjectively they reported

only seeing horizontal lines• They still reported

upper line longer than lower

• Shows visual system still processing sensory information

• Effect of hypnosis solely on conscious awareness

Hypnosis and Involuntary Control

• When under hypnosis people subjectively experience their actions to be involuntary

Can people be made to perform acts that are harmful to themselves or others?

• Evans & Orne (1965) told hypnotized subjects that cup of foaming liquid was ‘acid’

• Subjects could be induced to dip their hands in liquid and throw it in someone’s face

• However, control group when asked to simply pretend they were hypnotized

behaved in same way

• This behaviour can be explained in terms of “destructive obedience”; i.e., psychological

compliance with an authority figure

(Milgram, 1974)

• No evidence that hypnosis has a unique power to coerce people against their will

Why does hypnosis work?• There are two main competing explanations for

how hypnosis works:

• Dissociation (state hypothesis) Theory

• Social Cognitive (non-state hypothesis) Theory

Dissociation Theory • An altered state of consciousness

• Best known example is neo-dissociation theory proposed by Ernst Hilgard (1978)

• Cognition involves multiple systems of control not all conscious at same time

• These systems are controlled and motivated by central ‘executive ego’

Neo-dissociation Theory

• Hilgard argued that during hypnosis, hypnotist gains control of executive ego, and has access to various subsidiary control systems

• Hypnosis creates division of awareness/ person simultaneously experiences two streams of consciousness cut off from one another

• One stream responds to hypnotist’s suggestions, while second stream remains “hidden observer” of everything that occurs

‘Hidden Observer’ Phenomenon• Hilgard (1977) hypnotized subjects

and suggested they would not feel pain

• Placed arm in ice-cold water for 45 seconds and reported level of pain

• Another group Hilgard said “Perhaps there is another part of you that is more aware than your hypnotised part. If so, would that part of you report the amount of pain”.

‘Hidden Observer’ Study (Hilgard, 1977)

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Normal PainHidden ObserverHypnotized Subject

• Hilgard argued dissociation between streams of consciousness accounts for why hypnotism appears to produce involuntary actions

• Subject intentionally carries out actions, but only ‘hidden observer’ is aware

• Primary consciousness stream is cut off from this awareness and therefore action appears involuntary to subject

PAIN IMAGINED, PAIN PERCEIVED: shows regions activated during physically induced pain (left), hypnotically induced pain (middle), and imagined pain (right). In contrast to physically and hypnotically induced pain, imagined condition provided minimal activation in anterior cingulated cortex, insula, and secondary somatosensory cortex. Activation in primary somatosensory cortex was observed only during hypnotically induced pain. (S.W.G. Derbyshire et al., Neuroimage, 2004.)

Social Cognitive theory• Social cognitive theories deny that hypnosis

produces an altered state of consciousness.

• Instead hypnotic experiences result from expectations of people motivated to take on role of being “hypnotized”.

• Subjects develop a perceptual set – readiness to respond to suggestions and to perceive hypnotic experiences as real and involuntary

• Orne (1959) subjects told prior to being hypnotized that common feature of trance is stiffening of muscles in dominant hand

• Information false• When subjects were hypnotized, 55% spontaneously

displayed hand stiffening• No subjects in control group showed this behavior• Social Cognitive theory does not claim hypnotized people

are ‘pretending’ Expectations can influence behavior without conscious awareness (e.g., placebo effects)

Unhypnotized persons can also do this

hypnotist's words are gradually accepted without subject’s censorship of what is being said.

Hyper–suggestibility theorem

Summary• Hypnosis produces increased receptiveness to

suggestions • Hypnotized people subjectively experience their actions

to be involuntary.• Dissociation Theory attributes to divided streams of

consciousness.• Social Cognitive theory attributes this to subject’s

expectation as to what effect hypnosis will have on them

Hypnotherapy

•cessation of smoking (often in single session) • weight loss (body sculpting)•suppression of pain •hypnodontia – use of hypnosis in dentistry•enhance learning •reduce anxiety •Hypnodermatology - treating skin diseases with hypnosis.

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