It’s pretty clear that–in a fight–Darth Vader would crush Jar Jar Binks, Optimus Prime would beat Starscream, and Batman could pummel the Joker. Though some of these fictional characters don’t even look like humans, when it comes to strength, their voices give it all away. New research seems to confirm this: humans, like other animals, can accurately predict physical strength from voice alone.

In a study appearing today in The Proceedings of the Royal Society, researchers asked subjects to evaluate the upper-body strength of speakers from four distinct populations and language groups just by listening to their voices. Even when unfamiliar with a speaker’s language, listeners could tell which men might be good in a fight. The men they judged as sounding brawny were in fact physically stronger as measured by tests of hand grip, chest strength, shoulder strength, and bicep circumference.

As lead author Aaron Sell told Discovery News:

“Information about male formidability would have been important for both sexes over evolutionary time,” said Sell. “Both men and women would have benefitted from knowing who would likely win fights in order to make prudential alliances and for other reasons. Men would need this information to regulate their own fighting behavior. Women would also need this information in order to make effective mate choices.”

They study failed to make a similar link between women’s voices and strength. The study’s authors speculate that this is because early men were more likely to spar. The researchers also couldn’t determine what it was about certain male voices that made them sound strong–it wasn’t just a deep timbre–and say listeners may respond to a complex mix of cues.

For men, the finding proves especially interesting given the non-menacing statement researchers asked English speakers to say: “When the sunlight strikes raindrops in the air, they act like a prism and form a rainbow.” Apparently this sentence contains all the sounds of the English language, but those certainly aren’t fighting words.

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Image: flickr / ~ggvic~