Joseph C. Stevens John B. Pierce Foundation and Yale University
It is well known to scholars that Aristotle classified the human senses into five: vision, hearing, taste, smell, and touch. Less known is Aristotle's qualification that touch may comprise several "submodalities;" and, indeed, by the turn of the 20th century, thanks to the German physiologist Max von Frey, it became widely believed that the skin alone houses four separate senses: touch, pain, warmth, and cold ( Boring, 1942; Stevens & Green, 1978a). The issue whether warmth and cold may constitute a single modality, a view championed by von Frey's contemporary, Ewald Hering, rather than two separate modalities, seems to have become largely semantic. Various anatomical and psychophysical considerations argue for independence, others for interaction and continuity. The issue has been brilliantly elucidated by Hensel ( 1982). Thus, when warmth and cold receive here the labels "thermal senses," it is mainly for convenience rather than from a theoretical stance on their independence.
Broadly speaking, the thermal senses, like pain, taste, and smell, look perceptually and cognitively impoverished compared with vision and hearing. These latter are superbly fit to register spatial and temporal patterns of stimulation, enabling rich processing of information about the world we live in.