麻豆传媒

Your voice can give away a lot about you.. Humans can tell whether other people are taller or stronger than they are just by listening to them roaring.

To test this, Jordan Raine at the University of Sussex and his colleagues recorded roars made by actors in training at a London drama school. 鈥淲e did a pilot study beforehand and found that some ordinary people were really uncomfortable doing the roars. But the actors got really into it,鈥� says Raine.

He and his team instructed 31 men and 30 women to imagine themselves in a battle scenario as they were about to charge and attack, and then recorded them both roaring nonverbally, and aggressively shouting 鈥淭hat鈥檚 enough, I鈥檓 coming for you!鈥� They also measured each roarer鈥檚 height, and their strength as measured by handgrip strength and the circumference of their flexed bicep.

Ancestral cues

They played the recordings and asked listeners to say how much taller or shorter, and how much stronger or weaker, the person in the recording was compared to themselves. In 88 per cent of the trials, male listeners accurately identified those who were substantially stronger than them based on roars. Women did so in 77 per cent of the trials.

鈥淲e don鈥檛 know by what acoustic mechanism strength is encoded in verbal cues,鈥� Raine says. 鈥淏ut by roaring you are making yourself sound more formidable.鈥� It鈥檚 similar to roars and croaks seen across the animal kingdom.

鈥淏efore humans came into existence, before we shared a common ancestor with chimps, there鈥檚 every reason to believe this mechanism for assessing formidability was already present,鈥� says Aaron Lukaszewski at California State University, Fullerton. 鈥淭hat it was maintained and possibly elaborated in humans is not surprising, but it鈥檚 interesting.鈥�

Men tended to underestimate the relative strength of women based on their roars and aggressive speech, while women tended to overestimate the relative strength of men, and to a greater degree.

Height wasn鈥檛 correlated with strength, though both were accurately communicated through roars. Lukaszewski says that鈥檚 consistent with evidence that height may contain other types of information than physical formidability, such as age or maturity.

Men were more sensitive to height variation than women were, Raine says. Women rated men 5.5 to 16.5 centimetres shorter than them as 鈥渢aller鈥� 67 per cent of the time after hearing a roar.

Their perceptions may have been biased by the fact that on average men are taller than women, but this also adds to growing evidence that body size is less important than strength when it comes to mate choice, Raine says.