Spatial localization of warmth

This study explored the ability to localize warmth sensations produced by radiant stimulation of the forearm. The subject’s task was to state on which side of a tactile reference line warmth was perceived. Percentage correct improved with increasing intensity of the radiation, as well as with increasing distance from the reference line. There appears to be an inverse relation between the ability to make spatial judgments and the degree of spatial summation. At low levels of stimulation, intensity and area both contribute heavily to the magnitude of a warmth sensation and spatial localization is poor; but with increasing level, area contributes less and less to sensation and localization is better.