Functional measurement scales of painful electric shocks.

Abstract

Subjects were required to rate the combined intensities of two factorially paired shocks ranging in intensity from 1 mA through 2, 3, 4, and 5 mA. In Experiment 1, an anchored 1–20-point rating scale was used, and in Experiment 2, one of two scales, 1–15 points or 1–25 points, was provided to the subject. Data from all three conditions were fit by a weighted average model, Rij=wsi+(i−w)sj, where Rijs are mean ratings, si and sj are scale values of the first and second shocks, and w is a weight parameter. The derived psychophysical functions were linear in all three cases, and the slope increases with the number of available categories, in conformity to range-frequency theory. In a third experiment, subjects were divided according to the ratings they gave of pain elicited by the 5-mA shock. The weighted averaging model provided an appropriate integration model for both higher and lower pain raters. Higher raters tended to accord an equal weight to both shocks, whereas lower raters accorded greater weight to the second stimulus. Implications for research on analgesic procedures are discussed.