Deirdre Barrett, assistant clinical professor of psychology at Harvard Medical School, argues in her new book that our innate instincts are overstimulated, leading to hard-to-resist appetites: People are bombarded by food that they crave, tempted by seductive images, and urged to buy products designed to appeal to specific wants, regardless of need.

Rose Lincoln/Harvard Staff Photographer


Playing on our instincts

3 min read

Psychology professor says ‘supernormal stimuli’ drive many unnatural urges

Researchers have long known that lab animals’ behavior can be manipulated by artificially stimulating their natural instincts. Over-stimulating animals can provoke such extreme responses that they end up preferring artificial objects to the natural ones for which the instincts were designed.

Humans living in modern society are something like those lab animals, a Harvard psychology professor says. Like them, our innate instincts are overstimulated by unnatural products, as well as by advertising and images. And, like them, we respond almost unconsciously: reaching for more food, Web-surfing for porn, dumping time and money on “cute” toys, sitting for hours in front of televisions, and sending troops to fight a dehumanized “them.”

The difference between lab animals and us, however, is that overstimulation for animals isn’t present in nature. It can really only be found in the laboratory. If an animal escapes to its natural environment, it will return to natural stimuli and responses. For people, however, because we live in an artificial world of our own making, escaping those stimuli is not so easy.

But Deirdre Barrett, assistant clinical professor of psychology in Harvard Medical School’s Psychiatry Department, says that doesn’t mean there’s no hope for us.

Barrett, author of the new book “Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose,” says the first step is to understand what’s happening to us. Instincts and urges honed for hundreds of thousands of years to keep us alive in a world of scarcity are being subverted in the modern era of plenty. People are bombarded by food that they crave, tempted by seductive images, and urged to buy products designed to appeal to specific wants, regardless of need.

In her book, Barrett examines the history of research into supernormal stimuli, describing early behavioral experiments on birds and fish. In one, birds whose eggs were lightly speckled fell off as they tried to incubate ridiculously large, boldly polka-dotted fakes. In another, red-bellied male fish fought off artificial red-painted lures even when they didn’t look much like fish.

These outsized prods to normal instincts are called “supernormal stimuli,” and Barrett believes they’re present in our world today, sometimes quite intentionally, prodding us to buy and consume and do. It’s an easy sell, in many cases, because the stimuli give us a push to do things we’re already inclined toward.

Pornography, she said, subverts instincts intended for mating with people. Stuffed animals, dolls, and cartoon characters manipulate people’s preprogrammed affinity for childlike “cuteness.” She also looks at obesity, war, business, television, and even intellectual pursuits.

Though supernormal stimuli are not universally related to problems, Barrett said many of the episodes in her book do fall into that category. Understanding ourselves and the reasons we feel as we do, Barrett said, is the first step in overriding our instincts, in our being able to resist the siren song of the Big Mac.

She also recommended new government regulation to help limit supernormal stimuli, particularly in areas where public health may be at risk, and to “put normal back into our lives.” It might be easier to eat healthier foods, she said, if we lived in a food environment where we weren’t blasted by ads for “supernormal foods.”