April 14 (UPI) -- Scientists have underestimated the communicative abilities of the human scream, according to a new study.
After testing the different ways humans can use and perceive screaming as a communication tool, researchers determined screams can convey at least six different emotions.
The experimental findings, published this week in the journal PLOS Biology, showed human brains actually process non-alarming screams more efficiently than alarming screams.
Screams are deployed by a variety of nonhuman primates, as well as other mammalian species, to alert peers to danger and ward off would be rivals and predators.
But humans use screams as more than just a warning -- they're also used to express feelings of despair and elation.
Previously, studies have focused only on human alarm screams.
"Given that screams are of course relevant for alarm contexts, searchers simply forgot to look at positive contexts," lead author Sascha Frühholz told UPI in an email.
"The latter are relevant for humans, because maybe only humans scream in positive contexts -- joy and pleasure," said Frühholz, a neuroscientist at the University of Zurich in Switzerland.
To better understand the emotional range of the human scream, scientists had volunteers attempt to express a variety of emotions via screams.
"The screams that we used in our study were 'acted' screams, but we know that humans can produce acted screams that are very similar to spontaneous screams," Frühholz said. "And screaming is a 'natural' ability, new born babies scream as their first act in life. And we do not have to learn to scream."
Researchers then had another group of volunteers listen to and classify the screams into different emotional categories -- all while being observed using functional magnetic resonance imaging.
The analysis revealed six psycho-acoustically distinct scream types -- expressions of pain, anger, fear, pleasure, sadness and joy.
Surprisingly, listeners responded more quickly and showed higher neural activity in reaction to positive screams.
"Based on evolution and based on previous findings, one would assume that the human brain is more sensitive to alarm signals, because this can be life-saving in many contexts," Frühholz said. "Humans are sensitive to alarm screams, but they are much more sensitive to positive screams."
"Positive screams might have gained priority in humans, because most of our environments are safe; and positive emotions and screams are much more important for human interactions," Frühholz said.
"And as humans we actively seek contexts were we can produce positive screams -- for example, watching our favorite soccer team winning a match," Frühholz said.
In future studies, Frühholz and his research partners hope to explore the ways different screams are produced and perceived across cultures, as well as the ways humans screams are replicated using sound effects and music in horror movies.