Perception & psychophysics
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Sex differences in heat-pain and thermal sensitivity were investigated in 32 women (20 to 60 years of age) and 32 men (17 to 63 years of age) who had no somatosensory impairments. Pain thresholds were measured with stimuli of two different durations (phasic and tonic). Warmth and cold thresholds were assessed as indices of thermal sensitivity. ⋯ Women had significantly lower warmth thresholds than men (more pronounced on the foot than on the hand), but similar cold thresholds. Measures of body size (weight, height) correlated much more strongly with thermal than with pain sensitivity, and helped to explain the sex difference in the warmth threshold. A reduction of sex differences to body-measure differences appears likely, but could not be demonstrated unequivocally.
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Multidimensional scaling was used to explore whether a single intensity dimension underlies the perception of both nonpainful and painful electrical stimuli, or whether separate dimensions are required. For the scaling (INDSCAL) procedure, 41 healthy volunteers judged the similarity between all pairs of 16 intensities, which ranged from imperceptible levels to pain tolerance. For the property mapping (PREFMAP) analysis, they rated each intensity on each of 16 property scales. ⋯ Third and fourth dimensions, which refined the scaling of nonpainful stimuli, were also found. Variability in the subjects' use of the painful and nonpainful dimensions was related to their choice of stimulus descriptors. Like clinical pain, laboratory pain requires multidimensional assessment.