Swearing is a touchy subject, especially when it involves kids, but one researcher relates how to handle your child overhearing an errant expletive.

You’re driving in morning traffic when suddenly the car in your left lane swerves for the exit. You do two things instantly: Hit the brakes, and blurt an obscenity, a two-word phrase that would make your grandmother blush. When the danger has passed, you straighten out the wheel and feel a rush of relief. Then you hear a small voice from the back seat.
 
It’s your 4-year-old son, whom you’re driving to school. He asks matter-of-factly: “Daddy, what does that mean?” Then he proceeds to try the phrase out for himself. Often you can’t understand what your son is saying, but as he repeats the expletive, his diction is suddenly so clear that it’s as if he’s channeling Alistair Cooke. You sense that if you don’t say the right thing to him immediately, this phrase, of all the word combinations you’ve ever said to him, will enter his personal vocabulary directly and irrevocably.
            
If that scenario sounds roughly familiar, Timothy Jay, a professor of psychology at the Massachusetts College of Liberal Arts, has some advice: Relax. Swearing is certainly a touchy subject, especially when it involves children, but if people understood the issue a little more dispassionately, Jay says, they could gain valuable perspective.
            
Jay should know. Arguably the world’s expert on swearing, he has studied the use of what he calls “taboo words” for more than 35 years. In that time, he has challenged a number of common myths that surround cursing. For instance, Jay says, it’s a myth that people swear because they either can’t think of a better word or lack a proper vocabulary. “Turns out that people with better vocabularies and have a better command of the language also are the ones who know more swear words,” he says.
 
Also, contrary to popular belief, swearing does not indicate a lack of self-control, nor is the practice restricted to certain social classes or people withlittle education. Jay’s research proves conclusively that pretty much all fluent adult speakers know how to swear in their native language.

Jay has also discovered that the learning of those taboo words starts quite early. In two studies, one in 1980 and one in 2010, he trained researchers who had frequent contact with children to record every instance of swearing. By the time children enter kindergarten, Jay found, they’ve acquired all the rudiments of adult swearing and insulting. The average 3-4-year old has an impressive lexicon of some three-dozen swear words. (While some of the “swear words” in kindergarten circles include the sorts of words and phrases heard in G-rated movies, like “stupid” and “bum,” they also include several of the expletives common to, say, a Quentin Tarantino movie.) At this young age, girls actually have a larger cursing vocabulary than boys – although the boys soon catch up and surpass girls in both cursing vocabulary and frequency.
 
Of course, learning these words and using them are two different issues. So when parent’s hear them, Jay suggests, they should do what he has done in much of his own research: Focus on the context in which the word is used, not just the word choice itself, and respond to the underlying emotion. “Most of the time taboo words communicate emotion better than other words,” he says. “These emotions aren’t necessarily anger, but also joy, surprise and happiness. Swearing is like hitting the horn in your car.”

Taboo words are most commonly used to express a burst of anger, frustration or surprise. In darker moments, they’re employed to wound or humiliate others – think hate speech or sexual harassment. One recent study even found that swearing can momentarily reduce the pain of an injury. But the same words are also common parts of humor, storytelling and social commentary.

“When you say a taboo word in front of a child, the first thing you should realize is that it’s already too late,” Jay says. “By the time he’s repeating it, he’s already learned the word.” Children are language-learning machines; picking up new words, even unsavory ones, is what they’re built to do. While there is no reversing the process, you can console yourself with the knowledge that acquiring such words and phrases is a normal part of becoming fluent in a language.
 
Indeed, if kids are drawn to swear words, it’s because they intuitively grasp their power to express emotions. So if you find yourself awkwardly trying to explain a word you blurted out, it’s best to address why you said it, and move on. Try not to make to make too big a deal of the moment, Jay says; that only communicates that the words are important and meaningful.

“What I’d say in that situation is, ‘That’s something that daddy says when he’s angry, and he tries not to get angry and say that.’ Be to the point, and then shut up about it.” If it’s any consolation, Jay adds, your child will doubtlessly hear those words again.

Ethan Watters is a frequent contributor to The New York Times Magazine, Wired, Discover, and other magazines, and is the author most recently of Crazy Like Us: The Globalization of the American Psyche, which was recently published by Free Press.