Psychophysics is the branch of psychology dealing with the relationship between physical stimuli and their perception. While the majority of research has been done on vision, the discipline covers all the senses; papers have even been published on extrasensory perception, although more prosaic alternatives like hearing, taste, touch (including skin and enteric perception), and smell are the more prevalent.
Psychophysics studies psychological scales for physical stimuli. Hot and cold, for example, are psychological scalings of temperature stimuli for which such physical measures as degrees celsius provide only physical units.
Areas of investigation include sensory thresholds, methods of measurement of sensitivity, and signal detection theory.