Psychophysics is the branch of Psychology dealing with the study of relationship between physical stimuli and individual perception. Perception is a general concept which refers to interpretation of a stimuli received by the senses. The are number of factors that affect the perception. Even the same stimuli can give different perceptions at different situations. Some of the factors that affect the perception are the individual's expectations, similarity, proximity, continuity and closure.
The propounder of the concept or discipline of psychophysics was Gustav Theodor Fechner. The concept was first mentioned in his work Elemente der Psychophysik in 1860.