Want to psych out your opponent? Grunt!

Diane Mapes writes: Unnhh! Ahhrroooo!

Some sound like growls, others sound like sirens, but no matter what a tennis player's grunt sounds like, new research has found it actually helps by throwing their opponent off their game.

In a study conducted by Scott Sinnett, a psychology professor at the University of Hawaii, 33 undergraduate students watched tennis players hitting balls – with some of the tennis players grunting as they hit. Researchers then had the students indicate the direction of the shot immediately afterwards.