Evolution has over long stretches of time allowed species to deal adaptively with the basic problems of life in the prehistoric environment. However, with the rapid changes taking place in modern life, the glacial pace of the evolutionary changes no longer as easily allows species to adapt very well. This even affects us humans; for example, we are bombarded by a number of larger-than-life temptations such as supersized take-out food, candy bars, and improbable pornography, each of which impact on instinctive drives with dangerous results.
This is where supernormal stimuli come in. A supernormal stimulus is an exaggerated version of a stimulus that causes an instinctive behavior to take place.
In the 1930s Dutch ethologist Niko Tinbergen found that oystercatchers that lay small, pale blue eggs speckled with grey preferred to sit on giant, bright blue plaster dummies with black polka dots.
Using gulls, Tinbergen's students found that mother birds preferred to try feeding a fake baby bird beak held on a stick if the dummy beak was wider and redder than a real chick's.
Male stickleback fish ignored a real male to fight a dummy if its underside was brighter red than any natural fish. Tinbergen coined the term "supernormal stimuli" to describe these unreal substitutes. These stimuli appeal to primitive instincts; but paradoxically exert a stronger attraction than the real-life counterparts.
Most supernormal stimuli are contrived; though in rare cases they may occur in nature due to random variation. Since oystercatchers do not deliberately manufacture brightly-hued, oversized plaster eggs; that was not a factor in the oystercatcher’s environment. But the addition of a new element, the meddling by homo sapiens, changed the rules completely. Bird brains could not handle those supernormal stimuli.
Are humans affected by supernormal stimuli? Evolutionary psychologist Deirdre Barrett suggests in her book Supernormal Stimuli that we do: ours are mostly contrived: very sweet drinks, foods containing high amounts of fats (such as French fries or biscuits made with lard), stuffed animals with infantile features, and so forth. These specific stimuli in their naturally-occurring forms draw out instinctive patterns of behavior that make it easier to perform adaptive behaviors relating to survival or reproductive motives; however, in their excessive, supernormal condition they can possibly harm our physical or psychological well-being. (For example, we have an inborn preference for sweet-tasting substances as those ar related to increased energy; but the prehistoric environment did not have the superabundance of those that can be available very easily today.
Some examples in which the human perceptual environment has been changed through deliberate contriving can be seen in the form of toy animals with hyperinfantile features (e.g., Care Bears, My Little Pony), the use make-up, and with large-sized candy bars.
And we should not overlook supersized breast implants, once known as Bulgarian airbags. The story behind this slang expression is that a woman who had supersized in this way was in an automobile accident, but avoided serious injury because of the extra cushioning from her new breasts implants gotten in Bulgaria. Anyway, breasts that are sized out of the ordinary, whether due to nature or contrivance, are very likely to draw attention to the possessor. Maybe this is why larger-sized breast implants are more common in the L.A. and Las Vegas areas.
Barrett, Deirdre. Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose, W.W. Norton, NY, NY. 2009, 224 pp, IBSN 978-0393068481 US $24.95.