The effects of light, temperature, trance length, and time of day on hypnotic depth

We evaluated predictions derived from the ultradian theory of hypnosis regarding the effects of temperature, light, trance length, and time of day on reported trance depth in 95 college undergraduates. Temperature and light showed no relation to trance depth. However, as predicted by ultradian theory, subjects who were kept in trance for 15 minutes reported greater trance depth than those who experienced a 5-minute trance. Time of day interacted with subjects' self-reported time of peak alertness in the following way: Subjects who reported greatest alertness in the morning achieved greater trance depth in the morning than in the evening, whereas those subjects who reported greater evening alertness reported deeper trance in the evening than in the morning. This latter finding was inconsistent with ultradian theory and prior research. Alternative explanations for this finding are discussed. Overall, the results from the present study do not provide strong support for Rossi's ultradian theory of hypnosis.