The human scream signals more than fear of looming danger or entanglement in social conflicts. Screaming can also express joy or excitement. For the first time, researchers have demonstrated that non-alarming screams are even perceived and processed by the brain more efficiently than their alarming counterparts.

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 scream when experiencing strong emotions such as despair or joy as well. However, past studies on this topic have largely focused on alarming fear screams.

Humans respond to positive screams more quickly and with higher sensitivity

In a new study, a team at the University of Zurich Department of Psychology led by Sascha Frühholz investigated the meaning behind the full spectrum of human scream calls. The results revealed six emotionally distinct types of scream 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 Frühholz.

The research team carried out four experiments for their study. Twelve participants were asked to vocalize positive and negative screams that might be elicited by various situations. A different group of individuals rated the emotional nature of the screams and classified them into different categories. While participants listened to the screams, 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 scream 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. Researchers suggest that this may be due to the communicative demands brought about by humans’ increasingly complex social environments.