Master scaling of perceived intensity of touch, cold and warmth

A new approach is presented for scaling perceived intensity of touch, cold and warmth based on magnitude estimation. In this method named master scaling thenar is utilized as common reference area for scaling and calibrating perceived intensity. The master scaling is particularly well suited for clinical applications in which the stimulation in pain-affected body areas creates a complex perception (e.g., paradoxical heat for cold stimulation) and/or aberrant psychophysical functions for perceived intensity. The results from three different experiments showed that: (a) All patients and healthy subjects were able to scale adequately the perceived intensity of touch, cold, and warmth at unaffected body areas. (b) Thenar stimulations were shown to be adequate common references in the joint scaling of perceived intensity of other body areas in pain patients as well as healthy persons. (c) Individual thenar psychophysical functions can be used for screening patients and healthy persons with regard to their ability to scale perceived intensity of touch, cold and warmth. (d) Master scaled perceived intensity scales can be used for determining if various pain-unaffected body areas are normal or abnormal in patients and in healthy persons. (e) The interindividual variation in perceived intensity is considerably reduced after master scaling and approaches that of intraindividual variation as found in olfaction and hearing. Finally, empirically based thenar Master Functions of perceived intensity for touch, cold and warmth are proposed to be used in future sensory testing of patients, as well as of healthy persons.