Depending on your definition of course, I have yet to see proof that hypnosis exists at all.
On vacation, a guy passes through a reservation. An old Indian sat in front of a sign that proclaimed he had the worlds best memory. The traveller paid the $5 and ask him what he had for breakfast a year ago. The Indian replied, “Squash, two cornmeal tortillas and 4 quail eggs”. Impressed, the traveller thanked him and moved on.
The following year he passed the same way and again saw the native who claimed to have the worlds best memory. Seeing a chance to test his claims, he paid the Indian the $5 and asked his question: “what did you have for breakfast two years ago?”
The old Indian replied, “Didn’t you ask me that last year?”
However, it is associated with other disfunctions, like an inability to remember other things besides this information, and decreased mental processing power. So it seems that this is pushing right up against the boundaries, and that most normally functioning people would not have enough memory capacity for this.
Back in the day, my hypnosis lecturer (psychology was a secondary degree) was a professor who was a significant player in the field.
He persuaded me that hypnosis is real, because of a technique developed by Martin Orne called the real/simulator paradigm. The idea was for researchers to turn up aspects of hypnosis that could be used so that investigators who did not know who were the real patients and who were the simulators could distinguish “real” hypnotised individuals from highly motivated simulators. Kind of like a Turing test for hypnosis.
Turns out there are some tricks that investigators got very good at using to tell them apart.
I can’t now recall the details, but ISTR one related to telling the subject that the number 4 (or whatever) doesn’t exist, then telling them to do some calculation that will result in the answer 4, for example, “Whats 7 - 3?” Fakers applied logic to conclude that if 4 does not exist, the answer must be the next number down and say “3”. The genuinely hypnotised could not even attempt to answer the question and became highly distressed as they tried, but their hypnotic state did not allow them any answer even when at some level they instinctively knew there must be a simple one.
The professor also pointed us to research on the subject of memory. The idea that we can recover lost memories under hypnosis is highly problematic. For example, research has been done on people who only spoke English later in life. These people would then be regressed back in time to when they only spoke (say) German. Conversations like this would then occur:
Can you understand me now?
Nein.
Why can’t you understand me.
Ich spreche kein Englisch.
The internal contradiction is obvious. Something is happening here other than the recall of authentic memory.
Years later, my old professor gave evidence against my case when I was prosecuting an amateur hypnotist who molested a family of females. He made the point that memory of events that occur while under hypnosis can be highly unreliable, and the jury acquitted.