information:classification, structural:expansion
Susceptibility

Whereas the older "depth scales" tried to infer the level of "hypnotic trance" from supposed observable signs such as spontaneous amnesia, most subsequent scales have measured the degree of observed or self-evaluated responsiveness to specific suggestion tests such as direct suggestions of arm rigidity (catalepsy). The Stanford, Harvard, HIP, and most other susceptibility scales convert numbers into an assessment of a person's susceptibility as "high", "medium", or "low". Approximately 80% of the population are medium, 10% are high, and 10% are low. There is some controversy as to whether this is distributed on a "normal" bell-shaped curve or whether it is bi-modal with a small "blip" of people at the high end. Hypnotisability scores are highly stable over a person's lifetime. Research by Deirdre Barrett has found that there are two distinct types of highly susceptible subjects, which she terms fantasisers and dissociaters. Fantasisers score high on absorption scales, find it easy to block out real-world stimuli without hypnosis, spend much time daydreaming, report imaginary companions as a child, and grew up with parents who encouraged imaginary play. Dissociaters often have a history of childhood abuse or other trauma, learned to escape into numbness, and to forget unpleasant events. Their association to "daydreaming" was often going blank rather than creating vividly recalled fantasies. Both score equally high on formal scales of hypnotic susceptibility.