Julian Jaynes gives a highly interesting account of hypnosis. ("Hypnosis" Chapter 4, Book II)
Jaynes (1976/1990, pp. 380-383) points out that early forms of hypnosis were based on metaphorical interpretations. The first metaphor used in modern times is animal gravitation, of which, according to Anton Mesmer (1734 - 1815), Newton's (1643 -1727) gravitation is a special case. Mesmer then began to use the term animal magnetism from his association of magnetic attraction with gravitational attraction. His wild imagination did not stop there and he later began to use the metaphor of static electricity, the scientific concept popularized with the famous experiment by Benjamin Franklin (1706 - 1790). It seems that Mesmer just needed to authorize what he did to make it work with people of his age.
Jaynes uses his scheme of "metaphier/paraphier => metaphrand/paraphrand" to explain hypnosis.
In order to explain what he was able to do (later termed as hypnosis by James Braid), he used better known, and well accepted, words like "gravitation", "magnetism" and "static electricity" as metahiers. Together with the metaphiers were conveyed paraphiers, associations of the metaphiers, like penetrating or transferring power between things. Thus, his "trick" began to be accepted by people as a metaphrand, a novel concept familiarized by the metaphiers. Also accepted were parahrands like the penetrating or transferring power. Mesmer and his people shared this story.
Jaynes states (1975/1990, p. 383):
That the phenomenon of hypnosis is under the control of a collective cognitive imperative or group belief system is clearly demonstrated by its continual changing in history. As beliefs about hypnosis changed, so also its very nature.
Jaynes argues that the collective cognitive imperative was behind the phenomena known as hypnosis.
Jaynes (ibid) then cites the shift of the type of hyponsis from strange sensations and convulsions (with Mesmer), to spontaneous speech during trance state (a few decades after Mesmer), then to self-diagnosis of one's own illness (around 1825), and to responses that ought to happen if you believed in phrenology (and people believed this pseudo science at that time).
An interesting thing was that the new types of hypnosis had not been recoginzed before their appearaces (you may argue that if hypnosis were an objective (ie, human independent) phenomenon, the 'new' types of hypnosis must have been observed before they became popoular (there's nothing new under the sun!)).
New types of hypnosis continued but the above should be enough to make the point of the power of the collective cognitive imperative.
Here is Jaynes's summary (pp. 384 - 385):
It is not simply that the operator, Mesmer or Charcot or whoever, was suggesting to the pliant patient what the operator believed hypnosis to be. Rather, there had been developed within the group in which he worked a cognitive imperative as to what the phenomenon was 'known' to be. Such historical changes then clearly show that hypnosis is not a stable response to gven stimuli, but changes as do the expectations and preconceptions of a particular age.
Jaynes (p. 385) then cites the case of "stage hypnosis" as an example of demostrating the power of group expectation or belief (the same is true with feligious feeling and belief enhanced by crowds in churches and oracles by the throngs that attend them.)
It may be after all that 'trust' between people that make hypnosis possible.
Indeed, most students of the subject insist that there must be developed a special kind of trust relationship between the subject and the operator. One common test of the susceptibility to hypnosis is to stand behind the prospective subject and ask him to permit himself to fall voluntarily to see what it feels like to 'let go'. If the subject steps back to break his fall, some part of him lacking confidence that he will be caught, he almost invariably turns out to be a poor hypnotic subject for that particular operator. (Jaynes 1975/1990, p. 394)
What happens to consciousness at the time of hypnosis? Jaynes says that the consciousness of a subject under hypnotic trance is diminished.
Narratization is severely restricted. The analog 'I' is more or less effaced. The hypnotized subject is not living in a subjective world. He does not introspect as we do, does not know he is hypnotized, and is not constantly monitoring himself as, in an unhypnotized state, he does. (p. 387)
Jaynes argues that consciousness can be diminished because it is only a learned feature.
Learned features, such as analog 'I,' can uder the proper cultural imperative be taken over by a different initiative, and one such instance is what we cally hypnosis. (p. 398).
Consciousness is not the complete master of our actions. The narratization of the analog 'I' is only an attempt to monitor and partially control the self in the complexity of the world around him and the uncounscious impulses within him.
We live in a buzzing cloud to whys and wherefores, the purposes and reasonings of our narratizations, the many-routed adventures of our analog 'I's. And this constant spinning out of possibilities is precisely what is neccessary to save us from behavior of too impulsive a sort. The analog 'I' and the metahor 'me' are always resting at the confluence of many collective cognitive imperatives. (p. 402)
Narrative in self-referential consciousness is not the ultimate cause of our actions. Rather, it seems to me, it is a fleeting story of self-observation that you create to live in your learned, thus unnatural, environment, better known as society. You feel assurance by telling yourself your story. You feel empowered. If the story is shared by other people around you, you feel much more empowered. On a rare occasion, even to the extent to do what you don't usually do under the guidance from a hypnotist.
Julian Jaynes (1975/1990) The Origin of Consciousness in the Breakdown of the Bicameral Mind. New York: Mariner Books.
See also some Wikipedia articles.
History of hypnosis
Related articles in this blog:
Language and consciousness according to Julian Jaynes
Science of socially shared stories
Consciousness according to Julian Jaynes