The spots on the herring gull's lower mandible inspired some of the earliest work on supernormal stimuli.Henk Bogaard / Shutterstock

Everything is formed by habit. The crow’s feet that come from squinting or laughter, the crease in a treasured and oft-opened letter, the ruts worn in a path frequently traveled—all are created by repeatedly performing the same action.

Even neurons are formed by habit. When continuously exposed to a fixed stimulus, neurons become steadily less sensitive to that stimulus—until they eventually stop responding to it altogether.

Anything that’s habitually encountered—the landscape of a daily commute, storefronts passed on a walk to the bus stop, photographs arranged on a mantelpiece—tends toward invisibility. The more we see a thing, the less we see it. Familiarity breeds neglect.

Once perception settles into a comfortable pattern, we fall asleep to it. Only when the pattern is broken do we notice there is a pattern at all. The chains of mental habit are too weak to be felt until they are too strong to be broken, to paraphrase Samuel Johnson.

Wit, whether visual or verbal, can make the commonplace uncommon again by breaking the habits that render perception routine. We tend to define the quality of wit as merely being deft with a clever comeback. But true wit is richer, cannier, more riddling. And the best of it is often based on a biological phenomenon called supernormal stimuli.


The story of supernormal stimuli begins with the Dutch biologist Nikolaas Tinbergen. As a boy growing up in The Hague in the 1910s, Tinbergen was fascinated by the fish and fowl inhabiting the little pond in his backyard. These early encounters with the wildlife of the Netherlands informed his later work, and as an adult, he kept an aquarium in his home.

One day he noticed that the male three-spined sticklebacks—which have “gorgeous nuptial colors,” Tinbergen observed, “red on the throat and breast, greenish-blue on the back”—went into attack mode every time a red postal van parked outside. They dropped their heads and raised their dorsal fins, a posture normally assumed only in the presence of a rival male.

Wondering whether the fish were reacting to the postal van, Tinbergen introduced variously colored objects into the tank. He discovered that the males became aggressive in response to anything red—the unmistakable sign of another male’s presence—regardless of whether it resembled a fish. The observation sparked Tinbergen’s discovery of color’s influence on animal behavior, for which he shared the Nobel Prize in Physiology or Medicine in 1973.

When he wasn’t observing three-spined sticklebacks, Tinbergen spent a lot of time with adult herring-gull hens, which have pronounced orange spots on their lower mandibles. For the first few weeks of a chick’s life, its mother’s beak is its sole food source. That orange spot is a good target for chicks to aim at when they peck at their mother to prompt her to regurgitate food.

Tinbergen noticed that the chicks in his lab, like the male sticklebacks in his aquarium, aggressively pecked not just at their mother’s beak but at anything with an orange spot on it. It occurred to him that it might be possible to one-up nature, to “make a dummy that would stimulate the chick still more than the natural object,” he wrote.

So Tinbergen started making “super-gulls”: cobbled-together constructions that amplified the orange spot to which the chicks so enthusiastically responded. He painted orange spots on everything from old pieces of wood to kitchen utensils. He made the orange spots bigger and surrounded them with white rings to enhance the contrast. The chicks pecked at absolutely everything that had an orange spot on it. The bigger the spot, the more aggressively the chicks pecked.

Tinbergen called his exaggerated orange spots “supernormal stimuli,” which, he concluded, “offer stimulus situations that are even more effective than the natural situation.” This response to supernormal stimuli is not limited to herring gulls. Chicks from all species will beg for food from a fake bill if it has more dramatic markings than its parents have, and parents will ignore their own eggs and attempt to incubate much larger objects—including volleyballs—if those objects are decorated to resemble eggs.

Tinbergen theorized that human beings are susceptible to supernormal stimuli, too. The oversized eyes of stuffed animals, dolls, and cartoon characters are supernormal, he reasoned, kick-starting our instinctive response to nurture anything with infantile facial features. Sugar-saturated soft drinks, works of art, clothing, perfume, even lipstick—anything that intensifies or exaggerates an instinctive biological, physical, or psychological response—can be considered supernormal stimuli.


Supernormal stimuli are key to certain kinds of wit, too, deliberately skewing or exaggerating our usual patterns of perception. The great silent comic Buster Keaton is a case in point.

In The High Sign (1921), as Keaton settles down on a bench to read his local daily, he unfolds the paper to standard broadsheet format. He soon notices, though, that the newspaper is bigger than he expected, so he continues unfolding it—first to roughly the surface area of an ample picnic blanket, then easily to the proportions of a king-size bedsheet, until he’s finally engulfed by a single gigantic swath of newsprint.

In Seven Chances (1925), Keaton, a stockbroker on the verge of financial ruin, learns that he will inherit handsomely from his grandfather—if he weds by 7 p.m. When his sweetheart rebuffs him (she will marry for love, not for money), he places an open offer of marriage, with details of the pecuniary benefits, in the newspaper. Hundreds of women turn up at the church for the ceremony, only to become enraged at Keaton’s tactics. The bevy of would-be brides chases him out of town and onto a nearby hill, where he dislodges a single rock, which sets in motion an avalanche of boulders, which rain down on our hapless groom’s head.

Keaton’s gags start innocuously enough, with some ordinary object, then snowball into supernormal stimuli. But stimuli can also be made supernormal by visual or verbal tricks that disrupt the ordinary ways we see and understand the world.

Marcel Mariën’s work is rife with such tricks. Mariën started out as a photographer’s apprentice while still in his teens. But in 1935, after seeing the work of René Magritte for the first time, he decided on a career as an artist, soon becoming a close friend of Magritte and one of the most prominent of the Belgian surrealists. He worked in a variety of media—photography; film; collage; and “ready-mades,” works of art assembled from discarded materials, common household items, or unused parts of other objects.

In Star Dancer (1991), Mariën attached a doll’s high-heel shoe to one of the arms of a dead starfish, transforming it into a wispy, Matisse-esque ballerina. The strange juxtaposition makes the viewer do a double take. How can such a clearly alien creature have such distinctly human expressiveness? Like the volleyball/egg that birds try to incubate, the cobbled-together starfish/doll becomes a supernormal stimulus that alters viewers’ perceptions.

The same principle is at work in verbal wit. The English film director Anthony Asquith, for example, once introduced Jean Harlow, the platinum-blond 1930s Hollywood star, to his mother, Lady Margot Asquith, the author and wife of the longtime British prime minister Herbert Henry Asquith. Harlow mispronounced Lady Margot’s first name, sounding the final t, as in forgot. “The t is silent, my dear,” Asquith snipped, “as in Harlow.” Lady Margot isolated and exaggerated the significance of the simple t, just as Tinbergen isolated and exaggerated the herring gull’s orange spot, thereby dramatically enhancing its impact.

What is a punch line but a supernormal stimulus?

We respond to witty words and images more intensely than to “normal” objects, just as Tinbergen’s theory of supernormal stimuli suggests. “Humor at its best is a kind of heightened truth—a super-truth,” E. B. White wrote. This is also true of wit, which takes routine seeing and heightens it by shearing ordinary things and meanings of their habitual context, revealing them as suddenly strange and unfamiliar.


This piece was adapted from James Geary’s new book, Wit’s End: What Wit Is, How It Works, and Why We Need It.

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