The influence of external information on judgements of pain

Two studies were performed to assess the relationship between estimates of subjective pain and a graduated ischemic pain stimulus. In the first, 20 subjects received a 7-minute pressure stimulus with a blood-pressure cuff and then rated their pain on a 0-5 scale. At three separate sessions, subjects saw either no feedback or a visual feedback slide that ostensibly depicted cuff pressure. The numbers were either accurate, too high, or too low. Subjective estimates of pain rose with increasing cuff pressure, but pain ratings were higher during high-feedback conditions, and lower during low-feedback conditions than during either the no- or true-feedback conditions, which did not differ. Study 2, which evaluated subjective estimates of actual cuff pressure as well as pain, replicated these results. Both studies suggest that false information may alter a subject's report of pain and of the stimulus causing it.