But there has been limited past scientific scrutiny of the impacts of grunting. A 2014 study of college tennis players determined that grunting could indeed increase the power of players’ groundstrokes and serves. And a study from 2010 found that such sounds can be distracting for others. In that study, participants watched videos of a tennis player striking the ball while a loud, grunt-like yell played or did not. The viewers pressed keys to indicate their snap judgments about which side of the court, right or left, the ball was heading toward. When the stroke coincided with the noise, the viewers were noticeably slower and more inaccurate in their picks.

But those studies could not determine whether the usefulness of grunting was confined only to tennis or how the ballistic squawks were affecting onlookers and opponents. Were the screams masking the sound of the racket striking the ball, making it difficult for people to judge the right trajectories? Or were the sounds more directly distracting people, drawing their attention away from the onrushing ball and befuddling their reactions?

To learn more, some of the same scientists decided, for the new experiment, which was published last month in PLOS One, to look closely at mixed martial arts and grunting.

They chose that sport for several reasons, the first being that, like tennis, it demands sudden, explosive movements, meaning punches and kicks, to which grunting conceivably could add power.

Perhaps even more important, martial arts moves do not involve inherent noise, unlike the ping of a tennis racket meeting a ball. So if an onlooker proved to be worse at judging a fast-approaching kick when someone grunted, it would be because the yell had directly confused the watcher, not because it had masked some other noise.