Hypnotic susceptibility scales, which mainly developed in experimental settings, were preceded by more primitive scales, developed within clinical practice, which were intended to infer the "depth" or "level" of "hypnotic trance" on the basis of various subjective, behavioural or physiological changes.
Subsequently, the French neurologist Jean-Martin Charcot also made a similar distinction between what he termed the lethargic, somnambulistic, and cataleptic levels of the hypnotic state.
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.
Each form consists of motor and cognitive tasks but vary in their respective intended purpose.
Many professionals think that these tests produce results because they involve attentional control, and that a certain level of concentration is required to be hypnotized.
In 1981, Sherl Wilson and T X Barber reported that most of a group of extremely high hypnotizables who they termed "fantasizers".
The fantasizers exhibited a cluster of traits consisting of: 1) fantasizing much of the time, 2) reporting their imagery was as vivid as real perceptions, 3) having physical responses to their imagery, 4) having an earlier than average age for first childhood memory, 5) recalling "imaginary playmates" from childhood, and 6) having grown up with parents who encouraged imaginative play.
[7] In 1991, Deirdre Barrett examined a larger group of extremely high hypnotizables and confirmed that about 60% fit Barber and Wilson's characterization of fantasizers while 40% were what she termed "dissociaters" who: 1) experienced daydreaming mostly as "spacing out" and not remembering what had been going on for periods of time, 2) had later than average ages for first memories, and 3) had parents who had been harshly punitive and/or who had experienced other childhood traumas.
Fantasizers tended to experience hypnosis as being much like other imaginative activities while dissociaters reported it was unlike anything they'd ever experienced.