Multidimensional scaling of painful electrocutaneous stimulation: INDSCAL dimensions, signal detection theory indices, and the McGill Pain Questionnaire.

Individual-differences multidimensional scaling (INDSCAL) determined the dimensions underlying ratings of electrocutaneous stimuli, which ranged from innocuous levels to individual pain intolerance at each of three frequencies. Twenty-five healthy males made pairwise similarity judgments of these 15 stimuli for the INDSCAL procedure, and then rated each stimulus on nine property scales. Signal detection theory indices, as well as ratings on the McGill Pain Questionnaire (MPQ), were also obtained. A Sensory Magnitude dimension scaled the stimuli from lowest to highest perceived intensity; this dimension was related to sensory, affective, and arousal property scales. A Frequency dimension ordered the stimuli from lowest to highest frequency; this dimension was related to the Fast-Slow property. Compared to the Frequency dimension, the Sensory Magnitude dimension was more salient to subjects who better discriminated among painful stimulus intensities, set a more stoical pain report criterion, and were less apt to endorse frequency-related MPQ descriptors. Thus, variation of physical intensity and frequency elicited complementary dimensions of subjective judgment, which were related to perceptual and attitudinal differences among individuals.