Freshly Baked Science
Humans Roar- Now We Know Why
17th July 2018
If you’ve ever been to a zoo or safari park, you may have heard a lion roar, up close and personal. The sound they make is incredible and can be very intimidating! Vocalisations play an important role in the aggressive encounters of many mammal species. A noisy voice with a low pitch can help animals show off their deepness or masculinity to others.
The voice sound is changed by the length of the vocal tract. A bigger vocal tract usually means a bigger body size, which is a sign of good fighting ability. Roaring at each other is a great way for males to assess how challenging their rivals are without having to fight.
Some species have adaptations that take advantage of the relationship between body size and vocal tract length, exaggerating their size. For example, the red deer can lower its voice box all the way down to its breastbone, temporarily lengthening its vocal tract to make it sound that bit more threatening.
Are humans different?
It’s been assumed that humans roar for the same reason. Before now, nobody had studied whether human roars, like their nonhuman mammal equivalents, also communicate or exaggerate how intimidating someone is or whether we can judge from a voice alone whether someone is more powerful than us.
The University of Sussex measured 61 actors’ upper-body strength and height – both men and women – and asked them to produce aggressive roars and an aggressive sentence. They then measured 101 listeners’ upper-body strength and height and asked them to judge to what degree they thought each person they listened to was stronger/weaker or taller/shorter than them.
It was found that listeners could estimate the strength and height of vocalisers relative to themselves with high accuracy. The accuracy increased with the strength of the vocalisation, with error rates at as low as 6%!
Interestingly, in the study, women tended to overestimate men’s strength. Female listeners tended to rate male vocalisers of similar strength to themselves as stronger than them. Even in cases where males were weaker than female listeners, they were only correctly identified as weaker 25% of the time. This finding fits in with a general tendency for women to underestimate, and men to overestimate their abilities.
Humans are unique in being able to express complex concepts and emotions with speech, but it doesn’t mean we’re not animals – roars are among a wide range of human nonverbal vocalisations. So if you’re ever unfortunate enough to be roared at, remember that there’s useful information in there for you – but take that acoustic chest puff with a pinch of salt.
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