In his experiment, Dr. Stephens asked subjects to come up with a list of words, including swear words, that they might use if they hit their thumb with a hammer. Then they were asked to come up with a list of neutral words to describe a chair (like wooden, for example). He then asked them to submerge a hand in ice water for as long as they could, while repeating a word from either list: a swear word or a neutral one.

Participants who repeated a swear were able to keep their hand submerged in the ice water for almost 50 percent longer than those who repeated a neutral word. Not only that, swearing also made participants feel like the pain wasn’t as intense. Researchers concluded that swearing had the effect of reducing sensitivity to pain. Who knew four letters could be so soothing?

“For pain relief, swearing seems to trigger the natural ‘fight or flight’ stress response, as well as increased adrenaline and heart pumping,” Dr. Stephens said in an email. “This leads to stress-induced analgesia — being more tolerant of pain.”

Another study Dr. Stephens conducted, currently under review, tested the effect of swearing on strength. During bicycle and hand-grip exercises, researchers asked subjects to repeat curse words and neutral words while pedaling against resistance and squeezing a hand dynamometer, then recorded their results. In both cases, swearing improved performance.

Though swearing is mostly harmless, Dr. Bergen wrote in his book, slurs are the exception. There are clear benefits to using profanity, but when profanity targets demographic groups, it can foster prejudices, Dr. Bergen wrote.

Now, to clarify: These words, of course, don’t have any intrinsic, mystical power that confers superhuman strength and endurance. It is simply the act of speaking a taboo word that makes it cathartic, according to researchers, and that applies to emotional catharsis, too.