Ask A Genius 1554: Why Annoying Human Sounds Trigger Disgust
Author(s): Scott Douglas Jacobsen and Rick Rosner
Publication (Outlet/Website): Ask A Genius
Publication Date (yyyy/mm/dd): 2025/10/28
Why do ordinary human sounds like chewing or lip smacking trigger such strong feelings of disgust, and how does evolutionary psychology explain these instinctive reactions to perceived unfitness or poor hygiene?
Scott Douglas Jacobsen asks why ordinary bodily noises irritate us. Rick Rosner frames the reaction as evolutionary triage: humans quickly judge reproductive fitness, triggering instant attraction or the ick. Aversion to lip smacking, grunting, and loud chewing may signal traits like poor hygiene or impulsivity, maladaptive in mate choice. Disgust toward feces, blood, and exposed anatomy protects against disease and injury. Visible reminders of internal bodies, like open-mouth chewing, amplify repulsion. We also assess non-targets as competitors, and unease around extreme old age reflects selection pressures minimizing misdirected sexual interest. The interview explores instinct, culture, and biology behind everyday irritation.
Scott Douglas Jacobsen: An open philosophical question: why do certain normal human sounds annoy us? We evolved to make all these bodily noises. We’re embodied in these organic cages, making sounds—young or old—and yet some of those sounds irritate us. Maybe it’s cultural, maybe individual, but why does annoyance arise? Why do people react negatively to something like cottonmouth or throat smacking?
Rick Rosner: I just made a smacking sound there. With visceral reactions like that—especially in romantic contexts—people call it “getting the ick.” It’s when a potential partner says or does something that instantly turns you off sexually. I’d say that having an instant, instinctual reaction—positive or negative—to someone usually has to do with perceived reproductive fitness.
We’re deeply programmed by evolution to want to reproduce and to evaluate others for reproductive fitness. If it’s someone we’re sexually attracted to, we subconsciously assess their fitness as a mate. If they seem healthy and strong, that triggers desire.
If it’s someone of a gender we’re not attracted to, we still evaluate them, but as competition. Across the board, we’re also wired to be sensitive to signs of health. For instance, feces smell horrible to us, because they’re biologically dangerous. It’s unhealthy to get that stuff near your mouth or eyes. One of our dogs sometimes eats her own poop—it’s disgusting to us because evolution made it that way for a reason.
When people make certain noises—grunting, smacking their lips, chewing loudly—my guess is our aversion reflects something about perceived unfitness. Maybe it signals poor hygiene or impulsivity, traits that would’ve been bad for mate selection.
Why do we get grossed out when people chew with their mouths open and we can see their food? I’m not sure. That doesn’t map cleanly onto reproductive fitness. But I do think we’re repelled by visible reminders of what’s inside the body. We know what’s under the skin—blood, organs, muscle—and evolution has made us wary of that.
We don’t want to see people split open. It’s probably a survival adaptation: it would be bad for a species to be casual about injuries that reveal internal anatomy. That’s why blood and wounds cause such intense revulsion—we don’t want that happening to us or to anyone we care about.
Some people even get uneasy around the extremely old. Maybe that’s also tied to reproductive fitness—it does the species no good, evolutionarily speaking, to be sexually drawn to someone who’s eighty-three.
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