Interaction of intensity and order regarding painful events.

While stimulus intensity obviously affects degree of pain responding, presentation order effects of stimuli of different intensities on acute pain responses are under-researched. The present study examined the effects of manipulating presentation order of lower and higher pain stimulus intensity. Using 96 undergraduates, this investigation employed a 2 x 2 mixed research design, with pain stimulus sequence as a between-subjects variable and pain stimulus trial as a repeated measure. When the greater pain stimulus intensity was presented last, verbal report of pain was higher. Also, performance of a cognitive task was interrupted the least when the lower stimulus intensity was presented last. Heart rate, however, was highest when the greater stimulus intensity was presented first, and pain tolerance was greatest when the lower stimulus intensity was presented first. Results are discussed in relation to adaptation-level effects, and implications for pain experienced in clinical settings are suggested.