If seeing someone hurl makes you gag, too, and then launch into a puffed-cheek, double-hands-to-the-mouth, chest-heaving dance before you either toss your own cookies or scurry safely (and dryly) away, well, we owe you a compliment.
People who feel the urge to barf when witnessing another person throw up are both compassionate and highly evolved, say two medical experts on the stomach-turning topic.
“There's good news and bad news about why upchucking causes other people in the immediate vicinity to upchuck,” said Amy Morin, who teaches psychology at Kennebec Valley Community College in Fairfield, Maine and works a licensed clinical social worker.
“The good news is, if it happens to you, it means you have empathy,” Morin said.
In human brains, scientists have discovered “mirror neurons” that cause some people to feel the same emotions as others around us. This explains why you might tear up when you see someone in the room cry.
If that sounds like you, when you see someone vomit, your brain feels empathy and causes you to actually feel that disgust with the other person, and so the food in your gut wants to come out, explained Morin, who also writes for about.com at discipline.about.com.
“The bad news is, there's not much you can do about it. If you are prone to upchucking or gagging at the site, smell, or mention of vomit, your brain is likely fairly hard wired to react by doing so,” she added.
This wretched reaction is, in fact, still laced into our brains from ancient times – as a pure survival instinct, said Dr. Jennifer Hanes, an emergency physician at Northwest Hills Surgical Hospital in Austin, Texas.
"Humans are communal creatures, and if our ancestral brother began to vomit from spoiled food or other illness, likely we were exposed to the same pathogen as well,” said Hanes, author of "Lady in Weighting." "When one person vomits, our body begins to retch to expel the germs or poison that may be in our system, but (have) not yet reached a toxic level to cause illness on our own.
“If one member of the tribe is sick or poisoned, chances are the other members are as well so it developed as a self-preservation reflex. If it affects you, just think of yourself as highly evolved,” Hanes said, adding: she has never vomited in the ER but has witnessed the reflex with nurses and medical students.
In contrast, nurse Mary Pitman, calls on-the-job spewing her “single greatest weakness” in the emergency room.
“I have a theory on why one person hurling can turn a room into a vomitorium,” said Pitman, a Vero Beach, Fla. resident who has spent 31 years as a nurse. “Unlike my peers, for whom suctioning thick, green secretions out of someone's lungs is the ultimate stomach churner, mine is vomiting and here's why. It's a multi-sensory experience – there’s the sight, the sound, the smell and – most of all – the memory.
“Most people at some point have vomited. Seeing someone do it, and the sight of partially digested food, brings back that cascade of memories,” Pitman said. “And it's never good.”
Dang, she had to say "cascade."
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