Your brain perceives and processes non-alarming screams more efficiently than their alarming counterparts, researchers report.
Screaming can save lives. Non-human primates and other mammalian species frequently use scream-like calls when embroiled in social conflicts or to signal the presence of predators and other threats.
While humans also scream to signal danger or communicate aggression, they do it when experiencing strong emotions such as despair or joy as well. However, past studies on this topic have largely focused on alarming fear screams.
In their new study, the researchers investigated the meaning behind the full spectrum of human scream calls. The results revealed six emotionally distinct types of these calls indicating pain, anger, fear, pleasure, sadness, and joy.
“We were surprised by the fact that listeners responded more quickly and accurately, and with a higher neural sensitivity, to non-alarming and positive scream calls than to alarming screams,” says Sascha Frühholz of the psychology department at the University of Zurich.
The research team carried out four experiments for their study. They asked twelve participants to vocalize positive and negative screams that various situations might elicit. A different group of individuals rated the emotional nature of the calls and classified them into different categories. While participants listened, their brain activity underwent functional magnetic resonance imaging (fMRI) to monitor how they perceived, recognized, processed, and categorized the sounds.
“The frontal, auditory, and limbic brain regions showed much more activity and neural connectivity when hearing non-alarm screams than when processing alarm scream calls,” explains Frühholz.
It was previously assumed that human and primate cognitive systems were specially tailored for recognizing threat and danger signals in the form of screams. In contrast to primates and other animal species, however, human calls seem to have become more diversified over the course of human evolution—something that Frühholz considers to be a big evolutionary leap.
“It’s highly possible that only humans scream to signal positive emotions like great joy or pleasure. And unlike with alarm calls, positive screams have become increasingly important over time,” he says.
The researchers suggest that this may be due to the communicative demands brought about by humans’ increasingly complex social environments.
The research appears in PLOS Biology.
Source: University of Zurich