Measurement is an important catalyst for the advancement of science. As measurement techniques are developed, so is the ability of scientists to ask and answer important questions. Nowhere is this observation clearer than in the development of psychophysics. Psychophysics comprises a set of methods that allow for the precise determination of how a person's internal experience relates to external stimuli. The term psychophysics can be broken into two parts: psycho-, taken from psychology, refers to a person's internal experience, and physics refers to the features of the natural world to which the person is being exposed—that is, the stimulus. The combined word is thus defined as the measurement of how a person's experience is related to changes in the physical world. Psychophysics is not ...