In modern dating, the "ick" is primarily experienced by women and feared by men.
The term has gone viral on social media in recent years.
It describes a feeling of disgust toward the actions, appearances and other characteristics of someone’s partner.
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Some examples of popular icks include people chewing with their mouths open, wearing flip-flops or tripping over their own feet while walking.
The list has narrowed to a more specific set of icks blasted on the internet, including aversions to how men chase after a ping-pong ball, or even use a debit card instead of a credit card on a date.
National Geographic claims that the "ick" feeling is related to a biological, primal instinct.
In several primate species, including humans, adult females are "more sensitive to grossness than males," according to a scientific dive by NatGeo.
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"For instance, female gray mouse lemurs and Japanese macaques are more likely than males to turn up their noses at contaminated food, while female western lowland gorillas and olive baboons tend to avoid fellow animals with skin infections," the report noted.
This cautiousness then leads to a lower incidence of infectious disease in females, according to scientists.
Cecile Sarabian, a cognitive ecologist at the Institute for Advanced Study in Toulouse, France, told NatGeo that there’s a "protective power to the ‘yuck.’"
She suggested that females' pickiness about what they eat and who they expose themselves to "may be one of the reasons female primates live longer than males."
Elizabeth Anne Brown, a National Geographic contributing writer based in Denmark, commented on the findings.
"Scientists don’t know why lots of female animals — including humans — are more easily grossed out than males," she told Fox News Digital.
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"But ‘yuck’ acts like an advanced guard for our immune system, limiting our exposure to things that could make us sick, like parasites and bacteria."
Disgust "plays an important role" in mate selection for primates, Brown said, as females of some species "will absolutely shut down prospective suitors [who have] symptoms of STDs."
"If the resident male in a troop of western lowland gorillas develops pale blotches on his face — a symptom of infection with treponema, the same contagious bacteria that causes syphilis in humans — some females will fully abandon the troop and search for an uninfected male," she said.
"These female gorillas take ‘the ick’ so seriously that they basically skip town and start a new life."
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In analyzing Japanese macaques, Sarabian noted that the females would wipe off any leaf litter from their acorns before eating them, while the males were "more likely to gobble the food down having barely looked at it."
She added, "Unfortunately, the only dating advice we can take from our primate cousins is to be cautious about STDs — always a good policy."
Dr. Kyra Bobinet, a California behavioral neuroscientist and author of "Unstoppable Brain," broke down what happens in the brain when someone feels disgusted.
"Anything we are averse to, that we want to avoid, or that we shrink back from — including the ick — is controlled by this area of the brain [called the habenula]," she told Fox News Digital.
The habenula is a central part of the brain that’s involved in various important functions, including motivation and decision-making, according to the expert.
This area, when activated, "kills our motivation to try," said Bobinet.
"This area of your brain is scouting for anything that's not going to work out for you," she said. "It has a negativity bias."
The expert encouraged those who "get the ick" to try shifting their perception of the situation.
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Bobinet also agreed that women are biologically more prone to having self-awareness of "icky" feelings, as they are "made to make babies."
She said, "We have to be very sensitive to our environment because we have to protect the baby from fumes, from danger, from all these things."
The ick gets "taken to an extreme" on social media, according to Bobinet — "and you can get really narrowed down and too picky."
This can interfere with dating, the expert suggested, as criteria for a partner become "unrealistic."
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M. David Rudd, PhD, distinguished professor of psychology at The University of Memphis, said there are "undoubtedly evolutionary reasons" for disgust "across genders."
"But it’s important to always factor into today’s phenomenon the issue of social learning and related reinforcement driven by the broad and unparalleled reach of social media," he told Fox News Digital.
Rudd noted that social media creators are also motivated by attention and financial gain, which can move along trends more than "any meaningful evolutionary purpose."
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"Those most vulnerable to mimicking social media behavior are often those most in need of the central motivators to begin with — attention being the central one, quickly followed by money," he said.
