Comparison of verbal and visual analogue scales for measuring the intensity and unpleasantness of experimental pain

Although the multidimensional nature of pain is now well recognized, there are, nevertheless, very few quantitative tests to measure the separate dimensions of pain and little data concerning their relative sensitivity. The present study compares 2 currently available methods, verbal descriptor and visual analogue scales. Eight subjects rated painful and near-painful heat stimuli by using visual analogue scales for intensity or unpleasantness and by choosing the most appropriate phrases from lists of intensity or unpleasantness descriptors. In the intensity dimension, the relationship between perception and stimulus temperature was essentially identical whether calculated from the visual analogue or verbal descriptor scales. However, data derived from the verbal descriptor scales revealed that subjects rated the painful temperatures as relatively more intense than unpleasant; this difference could not be detected using the visual analogue scales. These results confirm that both visual analogue and verbal descriptor techniques successfully quantify sensory intensity and affective aspects of pain, but that verbal descriptors may provide the more sensitive tool for separating intensity and unpleasantness.