Validity and sensitivity of ratio scales of sensory and affective verbal pain descriptors: Manipulation of affect by diazepam

The results of two experiments suggest that sensory and affective verbal descriptors provide a valid scaling method which discriminates between the sensory intensity and the affect, or unpleasantness, of electrocutaneous stimuli. Twenty-four subjects judged the sensory intensity and affect of noxious electrocutaneous stimuli by choosing verbal descriptors from randomized lists and by cross-modality matching to time duration and to handgrip force. The psychophysical functions for sensory intensity generated by the descriptor and the cross-modality functions for sensory intensity generated by the descriptor and the cross-modality methods are the same. Psychophysical functions for affect generated by thedescriptor and the cross-modality methods are different. However, only the descriptor method produces psychophysical functions for affect that are significantly different from all the sensory functions. This result suggest that only the descriptor method distinguishes between sensory intensity and affect. The discriminative power of the descriptor method is demonstrated further in an experiment in which 32 subjects rated either the sensory intensity or the affect of the electrocutaneous stimuli immediately before and after an i.v. administration of 5 mg diazepam. This common minor tranquilizer significantly lowered affective descriptor responses (P less than 0.005) without altering sensory descriptor and sensory and affective handgrip responses. These experiments indicate that sensory and affective verbal pain descriptors may be used as a valid and sensitive tool for the evaluation of pain and pain control methods.