'Stimulation is the action of various agents (stimuli) on muscles, nerves, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity.
The word is also often used metaphorically. For example, an interesting or fun activity can be described as "stimulating," regardless of its physical effects on nerves.
A superstimulus or superreleaser is an exaggerated version of a stimulus to which there is an existing response tendency, or any stimulus that elicits a response more strongly than the stimulus that normally releases it.
It is sometimes argued that phenomena such as sexual fetishes and the taste for junk food can be partially explained as examples of superstimulation. Modern artefacts may activate instinctive responses which evolved in a world without shiny fabrics or double cheeseburgers, where shiny skin was a sign of health in a prospective mate, and fat was a vital nutrient.