Most theories of learning begin with a stimulus. To provide a background to educational psychology we should review these input devices. Moreover, An introduction to Physiological Psychology would be the logical agent we should use for our review.
Physiological psychology is a behavioral science.
The behavioral significance of a stimulus depends on its capacity to produce a neural impulse. Receptors convert environmental stimuli into neural impulses. The conversion process is known as transduction. The receptor is a biological transducer. Receptors share certain features with neurons.