response

In psychology, a stimulus is an energy change (such as light or sound) which is registered by the senses. In behaviorism and related stimulus’response theories, a stimulus constitutes the basis for behavior, whereas it constitutes the basis for perception in perceptual psychology. In the second half of the 19th century, the conception had been established by psychophysics, the “scientific study of the relation between stimulus and sensation”, together with the notion of the reflex arc constituting a foundational concept of scientific psychology. While at this time “whatever could be controlled by an experimenter and applied to an observer could be thought of as a stimulus.” In the context of perception, a distinction is made between the distal stimulus (the external, perceived object) and the proximal stimulus (the stimulation of sensory organs).