Supernormal stimulus

A supernormal stimulus or superstimulus 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 for which it evolved.

For example, when it comes to eggs, a bird can be made to prefer the artificial versions to their own, and humans can be similarly exploited by junk food. The idea is that the elicited behaviours evolved for the "normal" stimuli of the ancestor's natural environment, but the behaviours are now hijacked by the supernormal stimulus.