A supernormal stimulus 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 from which it evolved.
The Dutch ethologist and ornithologist Niko Tinbergen constructed an artificial stimulus consisting of a red knitting needle with three white bands painted around it. This elicited a stronger food-begging response among chicks than an accurate three-dimensional model of the Herring Gull’s white head and yellow bill with a red spot. Tinbergen and his students studied other variations of this effect, experimenting with dummy plaster eggs of various sizes and markings, finding that most birds preferred eggs with more exaggerated markings than their own, more saturated versions of their color, and a larger size than their own.
Harvard psychologist Deirdre Barrett argues that supernormal stimulation governs the behavior of humans as powerfully as that of animals. In her 2010 book, Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose, she examines the impact of supernormal stimuli on the diversion of impulses for nurturing, sexuality, romance, territoriality, defense, and the entertainment industry’s hijacking of our social instincts. In her earlier book, Waistland, she explains junk food as an exaggerated stimulus to cravings for salt, sugar, and fats and television as an exaggeration of social cues of laughter, smiling faces and attention-grabbing action.
An episode of the PBS science show NOVA showed an Australian beetle species whose males were sexually attracted to large and orange females, the larger and more orange the better. This became a problem when the males started to attempt to mate with certain beer bottles that were just the right color. The males were more attracted to the bottles than actual females.