Humans are capable of highly sophisticated language, but we also produce lots of “non-verbal vocalisations” – screams, moans and grunts – that scientists think provide clues about our evolutionary history.

Plenty of other animals used loud roars as a way of displaying strength and competing with each other for food and mates.

Aggressive roars may have a similar function in humans, and have been used on the battlefield by everyone from Roman soldiers to the Red Army.

“Thankfully most of us live in a safe and secure environment where we don’t have to experience roars, but in some situation they can still be a useful tactic,” Dr Jordan Raine at the University of Sussex told The Independent.

Dr Raine’s work has explored other non-verbal noises such as tennis grunts and noises made by people in pain, but in his latest study we wanted to find out if people were capable of making judgements about others based on vocalisations alone.

“Previous investigations have found that humans can estimate height and strength from the voice, but that they don’t do it very well,” he said. 

“However, no one has ever investigated to what extent people can judge whether someone is stronger or weaker than themselves.”

Such a judgement could have been useful for our ancestors, who may well have engaged in the same kind of vocal competition that creatures like red deer do to this day.

Dr Raine and his colleagues began by measuring the upper body strength and height of men and women, and then recording them making roars and speaking in an aggressive tone.

They then made the same measurements in a group of listeners, who were subsequently played the recordings.

Next the scientists asked the listeners to estimate how strong and tall the person shouting or speaking in the recording was in comparison to them.

When played the roars, male listeners were able to accurately identify whether the person in the recording was significantly stronger than them in nearly 90 per cent of trials, and never identified them as weaker.

They found that people were more likely to overestimate the strength of others when they were roaring compared with when they were speaking aggressively, and specifically they noted that women tended to overestimate men’s relative strength. The results were published in the journal iScience. 

This ability to use roars as a means of not only communicating an individual’s strength, but also exaggerating their abilities, is also seen in some animals. 

To Dr Raine, this serves as a reminder that there is less separating us from our animal relatives than we might assume.

“The findings we have found from all these papers suggest that these vocalisations communicate information that is relevant to our chances of survival and our chances of reproductive success,” he said.

“Despite out ability to produce complex speech, we are still privy to these non-verbal cues in the speech that reveal information about ourselves and influence how we think and act. It’s a window into our evolutionary origins, if you like.”

The Independent

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