On Sunday, Rick Santorum told ABC’s George Stephanopoulos that the idea of absolute separation of church and state “makes me want to throw up.” In October, the GOP candidate said he “almost threw up” reading John F. Kennedy’s 1960 speech on the topic. Can just thinking about something you find morally objectionable cause you to lose your lunch?
Sure—it’s called a visceral reaction. Vomiting is the body’s way of getting rid of toxins or poisons. The gastrointestinal system is controlled by interactions between the gut and the brain, and either one can send a signal that something is amiss. You might vomit because neurons in your digestive tract detect a chemical that shouldn’t be there, as when you ingest a harmful drug or contaminated shellfish. Or it might happen because neurons in your brain trigger nausea, similar to the process by which a stressful thought drives up your heart rate. If it’s strong enough, that nausea can override the gut’s normal functions, leading to what competitive eaters call a “reversal of fortune.”
A relatively straightforward example is sympathetic vomiting, in which the sight or smell of one person’s upchuck induces bystanders to follow suit. There may be an evolutionary explanation for this phenomenon: If your neighbor has ingested something harmful, there’s a chance you have, too. And if you haven’t, well, better safe than sickly.
The connection between the mind and the impulse to vomit has been established experimentally. Researchers long ago demonstrated that dogs which had come to associate a nauseating drug with a high-pitched sound could be made queasy by the sound alone, in an example of what psychologists now call classical conditioning. For cancer patients, the repeated experience of chemotherapy’s nauseating effects can induce vomiting from the moment they enter the treatment room.
Cognitive neuroscientists believe disgust is a primitive and universal human emotion, and it doesn’t have to be physical in origin to have physical effects. fMRI studies suggest that both disgusting images and foul odors activate the same brain structure, the anterior insula. The insula, in turn, triggers physical nausea. This process has been observed even in subjects who are merely shown pictures of other people looking disgusted, which might help to explain how one gets from abstract ideas to an upset stomach.
The close connection between disgust and the gut has become embedded in the way people think and talk about emotional responses—consider phrases like “I can’t stomach that” or “You make me sick.” Freud hypothesized that throwing up can be a symbolic act, an outward expression of the impulse to get a noxious thought out of one’s system.
As for why Santorum, in particular, has been made sick by the separation of church and state, it could be that he has an unusually sensitive stomach. A recent study suggests that people with stronger physiological responses to disgusting images, like a picture of a man with a mouthful of worms, are more likely to identify as politically conservative and to oppose gay marriage.
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Explainer thanks Douglas A. Drossman of the University of North Carolina and Peter Gott, M.D.
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