Maybe hypnosis is the right state of mind and ‘normal’ is really ‘under-hypnotised’?

That’s one idea that does not appear in the comprehensive synthesis of what we know about hypnosis produced by Terhune, Cleeremans, Raz and Lynn. It is a dense, concentrated document, thick with findings and sources, but they have done a remarkably good job of keeping it as readable as possible, and it’s both a useful overview and full of interesting detail. Terhune has picked out some headlines here.

Hypnosis, it seems, has two components; the induction and one or more suggestions. The induction is what we normally think of as the process of hypnotising someone. It’s the bit that in popular culture is achieved by a swinging watch, mystic hand gestures or other theatrical stuff; in common practice probably just a verbal routine. It seems that although further research is needed around optimising the induction, the details are much less important than we might have been led to think, and Terhune et al don’t find it of primary interest. The truth is that hypnosis is more about the suggestibility of the subject than about the effectiveness of the induction. In fact if you want to streamline your view, you could see the induction as simply the first suggestion. Post-hypnotic suggestions, which take effect after the formal hypnosis session has concluded, may be somewhat different and may use different mechanisms from those that serve immediate suggestions, though it seems this has yet to be fully explored.

Broadly, people fall into three groups. 10 to 15 per cent of people are very suggestible, responding strongly to the full range of suggestions; about the same proportion are weakly suggestible and respond to hypnosis poorly or not at all; the rest of us are somewhere in the middle. Suggestibility is a fairly fixed characteristic which does not change over time and seems to be heritable; but so far as we know it does not correlate strongly with many other cognitive qualities or personality traits (nor with dissociative conditions such as Dissociative Identity Disorder, formerly known as Multiple Personality Disorder). It does interestingly resemble the kind of suggestibility seen in the placebo effect – there’s good evidence of hypnosis itself being therapeutically useful for certain conditions – and both may be correlated with empathy.

Terhune et al regard the debate about whether hypnosis is an altered state of consciousness as an unproductive one; but there are certainly some points of interest here when it comes to consciousness. A key feature of hypnosis is the loss of the sense of agency; hypnotised subjects think of their arm moving, not of having moved their arm. Credible current theories attribute this to the suppression of second-order mental states, or of metacognition; amusingly, this ‘cold control theory’ seems to lend some support to the HOT (higher order theory) view of consciousness (alright, please yourselves). Typically in the literature it seems this is discussed as a derangement of the proper sense of agency, but of course elsewhere people have concluded that our sense of agency is a delusion anyway. So perhaps, to repeat my opening suggestion, it’s the hypnotised subjects who have it right, and if we want to understand our own minds properly we should all enter a hypnotic state. Or perhaps that’s too much like noticing that blind people don’t suffer from optical illusions?

There’s a useful distinction here between voluntary control and top-down control. One interesting thing about hypnosis is that it demonstrates the power of top-down control, where beliefs, suggestions, and other high-level states determine basic physiological responses, something we may be inclined to under-rate. But hypnosis also highlights strongly that top-down control does not imply agency; perhaps we sometimes mistake the former for the latter? At any rate it seems to me that some of this research ought to be highly relevant to the analysis of agency, and suggests some potentially interesting avenues.

Another area of interest is surely the ability of hypnosis to affect attention and perception. It had been shown that changes in colour perception induced by hypnosis are registered in the brain differently from mere imagined changes. If we tell someone under hypnosis to see red for green and green for red, does that change the qualia of the experience or not? Do they really see green instead of red, or merely believe that’s what is happening? If anything the facts of hypnosis seem to compound the philosophical problems rather than helping to solve them; nevertheless it does seem to me that quite a lot of the results so handily summarised here should have a bigger impact on current philosophical discussion than they have had to date.



  1. 1. Paul Torek says:

    Top-down control isn’t sufficient for voluntary control, but it isn’t necessary either. When I’m riding a bike, I don’t want top-down control over the angle of my body as I’m going around a curve. That would just put my top, down on the pavement. Ouch. I want my unconscious processes to handle that part. When they do, that’s entirely voluntary.

  2. 2. David Duffy says:

    I always think it strange that the work on semantic priming by the social psychologists (criticised extensively now because of the fragility of the effects) hasn’t taken advantage of our knowledge of suggestion in hypnotism – I get the impression it is still only a semi-respectable area of research, even now there are neuroimaging studies galore. Obviously, walking more slowly after reading lots of “old” words is suggestion at work. The (positive) correlation between intelligence and suggestibility is supposed to be pretty robust. My favourite study was trying to find out if being hypnotized into being the character made you a better actor in a play – IIRC they mumbled more.

  3. 3. Scott Bakker says:

    This a real gem–thank you, Peter!

    What hypnosis does seem to show is the slippery nature of our metacognitive capacities, how the capacity to flexibly direct resources at broadcast information perhaps includes the ability to slip off the plate altogether. Metacognitive filters are not only expensive things, they’re disastrous in circumstances demanding instantaneous decision-making. Having a ‘safemode’ for crisis situations, where the existential stakes guarantee cooperative communication, would be a communal boon. It would be interesting if hypnosis simply amounted to cuing this failsafe out of school, without the stress or stressors that render it adaptive otherwise.

  4. 4. Jorge says:

    I thought hypnosis was basically fringe (if not outright pseudo) science. And I’m not referring to the stage-act hokum, but just in general.

    Even if you accept that some people can enter a state of high susceptibility to suggestion (or related states like meditative trance), I don’t know how much that can tell us about consciousness in general.

  5. 5. David Duffy says:


    “…studies of the neural correlates of conscious experience should contrast conditions where the same physical stimulus elicits the same behavioral response, without and without accompanying conscious awareness…much of the neuroscientific literature on hypnosis has been motivated by the desire to demonstrate that hypnotic subjects are not faking – that hypnosis is real. At the same time, it should be pointed out that nobody ever questioned whether neuropsychological patients, such as the amnesic H.M., were faking. There is something of a paradox here, in that it sometimes seems as if the only self-reports that psychologists are prepared to believe come from persons who are brain-damaged!”

    From another good review:

  6. 6. Callan S. says:


    What would a natural trigger of hypnosis/safemode/no frills thinking mode look like?

    Would it be an individual triggered by a crisis into that mode and somehow the nature and expression of their mode triggers the state in others? Maybe that’s how human stampedes occur?

    Just hard to imagine an example of the originator, since hypnosis seems to be slow and require a quiet environment.

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