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these words to rate the pain intensity and unpleasantness of their clinical pain.


Furthermore, the investigators could systematically vary the magnitudes of the


experimental stimuli to establish“perceptual matches”between patients’clinical


pain intensity and unpleasantness and the experimental pain magnitude (Heft et al.


1980 ). Thus, the clinical match points are measured in the same units as the


experimental pain stimuli and could then be directly related to the stimulus–re-


sponse functions for the two dimensions of pain. As noted in thefigure, these


clinical match points lie close to the regression lines for these functions, demon-


strating that patients describe both clinical and experimental pain similarly and


reliably using the word rating procedure. Thus, ratings of experimental pain stimuli


can predict an individual’s rating of their clinical pain.


As shown in Fig.6.2 , visual analogue scales (VAS) provide another, similar


method, for assessing graded non-noxious (e.g., taste) and noxious experimental


stimuli. The VAS is a line (usually 100 or 150 mm length) whose end points have


labels that describe the extremes of sensation (e.g., for salty taste,“no salty taste,”and


“most intense salty taste imaginable”). Subjects then rate their sensation by placing a


mark on the line, and the dependent measure is the measured distance from the lower


endpoint to the mark. VAS for pain intensity and unpleasantness have been used to


assess both graded levels (ratio scales) of experimental and, also, clinical pain. (Price


et al.1983 ;Heftetal.1991 ). These visual analog scales are anchored by the labels


Fig. 6.2 Visual analogue scales for pain intensity and unpleasantness. Theupperfigurerepresents
a visual analogue scale for pain intensity. Thelinesare typically 150 mm with thelower endpoint
“No pain”and theupper endpoint“Most intense pain sensation imaginable.”Subjects rate their
pain intensity by placing a mark on theline. Thelowerfigurerepresents the visual analogue scale
for pain unpleasantness with thelower endpoint“Not unpleasant”and theupper endpoint“Most
unpleasant pain imaginable.”Subjects rate their pain unpleasantness by placing a mark on theline


108 M.W. Heft and M.E. Robinson

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