The human scream can communicate at least six distinct emotions, according to new research published in PLOS Biology.
Mammals frequently use screams to threaten aggressors or to indicate dangers in the environment. But – as we’re sure you’re aware – alarm and hostility are not the only causes for human screams. Delight and despair can also prompt a scream, for instance.
This study, carried out by researchers at the University of Zurich in Switzerland, asked twelve participants to scream after imagining a specific scenario: for instance, being attacked in a dark alley or their favourite sporting team winning a World Cup. Each scenario correlated to one of six emotions: pleasure, sadness, joy, pain, fear, and anger. Each scream was recorded, along with a ‘neutral’ scream: “an intense vocalisation of the vowel /a/”, according to the paper. The researchers carried out an acoustic analysis of the screams, along with using machine learning to assess the difference between them.
Previous research showed that an acted and genuine scream were indistinguishable to a listener.
The researchers then asked 33 other study participants to rate and classify the screams while listening to them. These participants also had MRI scans while listening to each noise.
The listeners were able to distinguish the six emotions that prompted the screams. Interestingly, they responded faster and with higher neural sensitivity to positive calls.
“The results of our study are surprising in a sense that researchers usually assume the primate and human cognitive system to be specifically tuned to detect signals of danger and threat in the environment as a mechanism of survival,” says Sascha Frühholz, lead author on the paper.
“While this seems true for scream communication in primates and other animal species, scream communication seemed to have largely diversified in humans, and this represents is a major evolutionary step. Humans share with other species the potential to signal danger when screaming, but it seems like only humans scream to signal also positive emotions like extreme joy and pleasure.
“Signalling and perceiving these positive emotions in screams seemed to have gained priority in humans over alarm signaling.”
Ellen Phiddian is a science journalist at The Royal Institution of Australia.
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