What is self-hypnosis?
All hypnosis is really self-hypnosis. The person inducing hypnosis doesn't do anything to a person or control them in any way. Medical professionals are just teaching people how to narrow their focus of attention, turn inward and put outside of conscious their awareness of some things that would ordinarily be in consciousness.
The only time I formally hypnotize a patient is the first time when I am assessing their hypnotizability. After that, I teach people how to enter the state for themselves. Since hypnosis is not sleep, but rather highly focused attention, it's a state you can enter into very quickly if you've got the ability. You can monitor what you're doing while you're in it, and you can choose to end it when you want to.
How do you determine someone's receptiveness to hypnosis?
I do a five-minute test called the hypnotic induction profile. I give people a series of standard instructions for hypnotic experience. I'm basically seeing whether they have the capacity to experience these hypnotically instructed alterations in perception, sensation and motor control. To evaluate their sensory alternation, for example, I ask them to imagine that their hand is light and floating up in the air. If they pull it down, it will float right back up.
It turns out that hypnotizability in adult life is an extremely stable trait. It's as stable as IQ. The peak period of hypnotizability in the human life cycle is children between the ages of 5 and 10. Most 8-year-olds are in trances most of the time. You know, you call them in for dinner and they don't hear you. So it's actually quite easy for most children to go into hypnotic state.