Braid worked very closely with his friend and ally the eminent physiologist Professor William Benjamin Carpenter, an early neuro-psychologist who introduced the "ideo-motor reflex" theory of suggestion. Carpenter had observed instances of expectation and imagination apparently influencing involuntary muscle movement. A classic example of the ideo-motor principle in action is the so-called "Chevreul pendulum" (named after Michel Eugène Chevreul). Chevreul claimed that divinatory pendulae were made to swing by unconscious muscle movements brought about by focused concentration alone.
“Before attending the Hypnotherapy Academy of America, I had already had over 500 hours of hypnotherapy training; however, I felt that I was missing some important concepts and skills, so I went to the Academy hoping to get what I was unable to get from other training. My goals were completely fulfilled. I received a solid foundation in hypnosis and hypnotherapy and learned how to take hypnotherapy to new heights and greater depths. As a result of the Academy training, I now do hypnotic work more efficiently and more effectively than with my prior training. Because the quality of my work as a hypnotherapist has significantly improved through the Academy training, I can offer greater value to my patients, and I can more easily market my practice.
The next major development came from behavioural psychology in American university research. Clark L. Hull (1884–1952), an eminent American psychologist, published the first major compilation of laboratory studies on hypnosis, Hypnosis & Suggestibility (1933), in which he proved that hypnosis and sleep had nothing in common. Hull published many quantitative findings from hypnosis and suggestion experiments and encouraged research by mainstream psychologists. Hull's behavioural psychology interpretation of hypnosis, emphasising conditioned reflexes, rivalled the Freudian psycho-dynamic interpretation which emphasised unconscious transference.
Hypnosis is not a unitary state and therefore should show different patterns of EEG activity depending upon the task being experienced. In our evaluation of the literature, enhanced theta is observed during hypnosis when there is task performance or concentrative hypnosis, but not when the highly hypnotizable individuals are passively relaxed, somewhat sleepy and/or more diffuse in their attention.
High hypnotizable people with PHA typically show impaired explicit memory, or difficulty consciously recalling events or material targeted by the suggestion, and a dissociation between implicit and explicit memory, so that even though they can’t recall the forgotten information it continues to influence their behavior, thoughts and actions. The forgetting is reversible—when the suggestion is cancelled, their memories come flooding back. These last two features—the dissociation and reversibility—confirm that PHA is not the result of poor encoding of the memories or of normal forgetting, because the memories return as soon as PHA is cancelled. Rather, PHA reflects a temporary inability to retrieve information that is safely stored in memory. That makes it a useful tool for research.
“My hypnotherapy business is humming along. Within less than a year of graduating, I am doing between 8 and 15 sessions per week now! I love my work and give thanks to God every day for the opportunity to help others. I wouldn’t be where I am today, having these successful outcomes, if it were not for the thorough training I received at the Hypnotherapy Academy. My confidence is strong and unwavering. It still amazes me how easily this all came together and continues to do so! And my thanks to Susan for the sessions I received while at the Academy, they worked wonders for me in so many ways.”
This finding—that PHA temporarily disrupted some people’s ability to recall the past—echoes decades of hypnosis research. What is entirely new in Mendelsohn et al.’s study is their demonstration that PHA was associated with a specific pattern of brain activation. Consistent with what normally occurs in remembering, when people in the non-PHA group performed the recognition task and successfully remembered what happened in the movie, fMRI showed high levels of activity in areas responsible for visualizing scenes (the occipital lobes) and for analyzing verbally presented scenarios (the left temporal lobe). In stark contrast, when people in the PHA group performed the recognition task and failed to remember the content of the movie, fMRI showed little or no activity in these areas. Also, fMRI showed enhanced activity in another area (the prefrontal cortex) responsible for regulating activity in other brain areas.
There are numerous applications for hypnosis across multiple fields of interest, including medical/psychotherapeutic uses, military uses, self-improvement, and entertainment. The American Medical Association currently has no official stance on the medical use of hypnosis. However, a study published in 1958 by the Council on Mental Health of the American Medical Association documented the efficacy of hypnosis in clinical settings.
Braid made a rough distinction between different stages of hypnosis, which he termed the first and second conscious stage of hypnotism; he later replaced this with a distinction between "sub-hypnotic", "full hypnotic", and "hypnotic coma" stages. Jean-Martin Charcot made a similar distinction between stages which he named somnambulism, lethargy, and catalepsy. However, Ambroise-Auguste Liébeault and Hippolyte Bernheim introduced more complex hypnotic "depth" scales based on a combination of behavioural, physiological, and subjective responses, some of which were due to direct suggestion and some of which were not. In the first few decades of the 20th century, these early clinical "depth" scales were superseded by more sophisticated "hypnotic susceptibility" scales based on experimental research. The most influential were the Davis–Husband and Friedlander–Sarbin scales developed in the 1930s. André Weitzenhoffer and Ernest R. Hilgard developed the Stanford Scale of Hypnotic Susceptibility in 1959, consisting of 12 suggestion test items following a standardised hypnotic eye-fixation induction script, and this has become one of the most widely referenced research tools in the field of hypnosis. Soon after, in 1962, Ronald Shor and Emily Carota Orne developed a similar group scale called the Harvard Group Scale of Hypnotic Susceptibility (HGSHS).
Take any bright object (e.g. a lancet case) between the thumb and fore and middle fingers of the left hand; hold it from about eight to fifteen inches from the eyes, at such position above the forehead as may be necessary to produce the greatest possible strain upon the eyes and eyelids, and enable the patient to maintain a steady fixed stare at the object.
Controversy surrounds the use of hypnotherapy to retrieve memories, especially those from early childhood or (supposed) past-lives. The American Medical Association and the American Psychological Association caution against recovered-memory therapy in cases of alleged childhood trauma, stating that "it is impossible, without corroborative evidence, to distinguish a true memory from a false one." Past life regression, meanwhile, is often viewed with skepticism.
Cognitive behavioural hypnotherapy (CBH) is an integrated psychological therapy employing clinical hypnosis and cognitive behavioural therapy (CBT). The use of CBT in conjunction with hypnotherapy may result in greater treatment effectiveness. A meta-analysis of eight different researches revealed "a 70% greater improvement" for patients undergoing an integrated treatment to those using CBT only.