The effects of suggested analgesia on radiant heat pain as a function of hypnotic susceptibility: a signal detection analysis

The present study investigated the effects of suggested analgesia and level of hypnotic susceptibility (high vs. low) on acute radiant heat pain using a signal detection theory model. A signal detection paradigm was used in order to differentiate between sensitivity (sensory-discriminative) and respose bias (motivational-affective) components of pain. Treatments consisted of: (1) a suggested analgesia group, and (2) an expectancy control group. Both groups had equal numbers of high and low scorers on a scale of hypnotic susceptibility.

Subjects were 32 male and female undergraduate volunteers assigned equally to each of the two treatment groups and counterbalanced for level of hypnotic susceptibility. Five levels of radiant heat (including zero) were presented. Each subject received 30 stimulus presentations per level and rated each stimulus on a scale from zero to six, with seven being a withdrawal. Self-report inventories of trait and state anxiety were also taken. Subjects participated in pre- and posttreatment sessions of radiant heat stimulation and were given three training sessions in the interim.

Results were that sensitivity measures showed a significant decrease for the suggested analgesia group for all but the highest stimulus level paired comparison. There was also a decrease in sensitivity for the expectancy control group for the lowest stimulus pair.

Measures of response bias for a report of pain or higher changed nondifferentially across groups and levels, except for the highest stimulus pair, for which the experimental group showed a significant hesitancy to respond relative to the control group. There were no significant difference in terms of treatment effects for high vs. low hypnotic susceptibility.

Mean pain ratings decreased for both groups. Trait anxiety did not but state anxiety did decrease significantly after treatment.

Results were taken as supporting Gate Control Theory and a figure-ground realignment model of pain. Suggestions were made for directions in future research.