Thermal cues and the perception of force.

Two experiments were conducted to examine the effect of temperature on force perception. The objective of the first experiment was to quantify the change in skin temperature of the finger as a function of contact force, in order to characterize how much temperature changes under normal contact conditions. The decrease in temperature ranged from 2.3 to 4.2 degrees C as the force increased from 0.1 to 6 N, averaging 3.2 degrees C across the nine force levels studied. The changes in temperature as a function of force were well above threshold, which suggests that thermal cues could be used to discriminate between contact forces if other sources of sensory information were absent. The second experiment examined whether the perceived magnitude of forces (1-8 N) generated by the index finger changed as a function of the temperature of the contact surface against which the force was produced. A contralateral force-matching procedure was used to evaluate force perception. The results indicated that the perceived magnitude of finger forces did not change as a function of the temperature of the reference contact surface which varied from 22 to 38 degrees C. These results provide further support for the centrally generated theory of force perception and indicate that the thermal intensification of tactually perceived weight does not occur when forces are actively generated.