Study finds that human brains react faster to non-alarming screams
A new study has revealed that a human scream can convey a complex range of emotions beyond fear and danger, and that our brains perceive and respond to them in different ways. Counter-intuitively, the study – which involved the use of brain-scanning technology – showed that there was relatively little neural response to alarming screams when compared to their non-alarming counterparts.
Many mammal species – including primates like monkeys and apes – have evolved to live in social groups, and to share responsibilities. One of the benefits of living in a group is that a member of the community can communicate danger to anyone nearby in the form of an alarm-like scream.
These vocal outbursts are loud, high-pitched and intense, and so are easily recognized by other members of the social community. Humans are just one of the many species that have evolved to scream in response to perceived threats or surprise. However, according to the results of a new study, a scream is far more complex than a simple alarm mechanism.
The team behind the research sought to shed light on how humans process and understand different types of screams.
A group of 12 volunteers were asked to vocalize screams triggered by a varying set of circumstances, such as fear and pleasure. A separate set of study participants were then tasked with categorizing the emotional quality of the screams while having their brains scanned using functional magnetic resonance imaging (fMRI).
The researchers concluded that human screams fell into six distinct categories, with those being joy, anger, sadness, pleasure, fear and pain. The fMRI scans also revealed details on how easily the different types of screams were to identify, and how long it took the study participants to react to them.
Counterintuitively, the results showed that non-alarm screams, such as those caused by joy, were processed and reacted to faster than their more negative counterparts, which triggered relatively low perceptual sensitivity in the brain.
"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," explains Dr. Sascha Frühholz of the University of Zurich, one of the authors of a paper on the study. "This has long been supposed to be the primary purpose of communicative signalling in screams."
According to the researchers, this suggests that human screams are more diverse than those of primates and that at some point, likely as a result of living in more complex social structures, our brains have evolved to give non-alarming screams greater priority.
The paper has been published in the journal PLOS Biology.