nancy_etcoff's picture
Psychologist and faculty member of the Harvard Medical School and of Harvard University
Supernormal Stimuli

Humans and other animals fall for hyperbole. Exaggeration is persuasive; subtlety exists in its shadows. In a famous set of studies done in the 1950s, biologist and ornithologist Niko Tinbergen created “supernormal stimuli,” simulacra of beaks and eggs and other biologically salient objects, that were painted, primped and blown up in size. In these studies herring gull chicks pecked more at big red knitting needles than at adult herring gull beaks, presumably because they were redder and longer than the actual beaks. Plovers responded more to eggs with striking visual contrast (black spots on white surround) than to natural but drabber eggs with dark brown spots on light brown surround. Oystercatchers were willing to roll huge eggs into their nests to incubate. Later studies, as well as recording in the wild show supernormal stimuli hijacking a range of biologically driven responses. For example, female stickleback fish get swollen bellies when they are ripe with eggs. When Tinbergen’s student, Richard Dawkins made the dummy rounder and more pear shaped greater lust was inspired. He called these dummies “sex bombs.” Outside of the lab, male Australian jewel beetles have been recorded trying to perform sex with beer bottles made of shiny brown glass whose light reflections resemble the shape and color of female beetles.

Research on the evolution of signaling shows that animals frequently alter or exaggerate features to attract, mimic, intimidate, or protect themselves from conspecifics, sometimes setting off an arms race between deception and the detection of such deception. But it is only humans who engage in conscious manipulation of signals using cultural tools in real time rather than relying on slow genetic changes over evolutionary time. We live in Tinbergen’s world now, surrounded by supernormal signals produced by increasingly sophisticated cultural tools. We need only compare photoshopped images to the un-retouched originals, or compare, as my own studies have done, the perceptions of the same face with and without cosmetics to see that relatively simple artificially created exaggerations can be quite effective in eliciting heightened positive responses that may be consequential. In my studies the makeup merely exaggerated the contrast between the woman’s features and the surrounding skin.

How do such signals get the brain’s attention? Studies of the brain's reward pathways suggest that dopamine plays a fundamental role in encouraging basic biological behaviors that evolved in the service of natural rewards. Dopamine is involved in learning, and responds to cues in the environment that suggest potential gains and losses. In the early studies of the 1950s, before the role of dopamine was known, scientists likened the effects of supernormal stimuli to addiction, a process we now know is mediated by dopamine.

Are superstimuli leading to behavioral addictions? At the least, we can say that they often waste time and resources with false promises. We fall down rabbit holes where we pursue information we don’t need, or buy more products that seem exciting but offer little of real value or gain. Less obviously, they can have negative effects on our responses to natural stimuli, to nutritious foods rather than fast foods, to ordinary looking people rather than photoshopped models, to the slow pleasures of novel and nonfiction reading rather than games and entertainment, to the examined life rather than the unexamined and frenetic one.

Perhaps we can move away from the pursuit of “supernormal” to at least sometimes considering the “subtle” and the “fine,” to close examination and deeper appreciation of the beauties and benefits that lie hidden in the ordinary.