Referred thermal sensations: warmth versus cold.

The present study investigates further the phenomenon of thermal referral, in which thermal sensations are "referred" to the site of nearby tactile stimuli. First demonstrated with three stimulators (Green, B.G. Perception and Psychophysics, 1977, 22, 331-337), the present experiments show that referral also occurs between two contact stimuli. Measurements with two stimulators reveal that (1) on the arm and fingers, warmth refers more strongly that cold, and (2) referral of warmth is affected relatively little by increasing the distance between stimulators; (3) on the fingertips, referral is greater when the thermal sensation refers away from rather than toward the first digit; and (4) the pattern or referral across fingers differs for warmth and cold and appears unrelated to the pattern of peripheral innervation. The phenomenon of referral illustrates that information about locus gathered through the tactile sense is available to the thermal senses, which means that information about stimulus locus and quality can be carried on separate nerve fibers.