Psychophysics is the study of the relationship between the physical aspects of stimuli of our psychological experience of them. Psychophysics played a central role in the development of the field of psychology and many of the first psychologists studied issues related to psychophysics.
Psychophysics is the study of the relationship between external stimuli from the physical world and the subjective sensations they produce. The psychological processes involved are still as much a part of the subject matter of experimental psychology as they were when these problems were studied in the first psychological laboratories established in the 1870s.