Screams of joy appear to be easier for our brains to comprehend than screams of fear, a new study suggests. The results add a surprising new layer to scientists’ long-held notion that our brains are wired to quickly recognize and respond to fearful screams as a survival mechanism (SN: 7/16/15).
The study looked at different scream types and how listeners perceive them. For example, the team asked participants to imagine “you are being attacked by an armed stranger in a dark alley” and scream in fear and to imagine “your favorite team wins the World Cup” and scream in joy. Each of the 12 participants produced seven different types of screams: six emotional screams (pain, anger, fear, pleasure, sadness, and joy) and one neutral scream where the volunteer just loudly yelled the ‘a’ vowel.
Separate sets of study participants were then tasked with classifying and distinguishing between the different scream types. In one task, 33 volunteers were asked to listen to screams and given three seconds to categorize them into one of the seven different screams. In another task, 35 different volunteers were presented with two screams, one at a time, and were asked to categorize the screams as quickly as possible while still trying to make an accurate decision about what type of scream it was, either alarming screams of pain, anger or fear or non-alarming screams of pleasure, sadness or joy. It took longer for participants to complete the task when it involved fear and other alarming screams, and those screams were not as easily recognizable as non-alarming screams like joy, the researchers report online April 13 in PLOS Biology.
In another experiment, 30 different volunteers underwent functional magnetic resonance imaging, or fMRI, while listening to the screams. Less-alarming screams elicited more activity in the auditory and frontal brain regions than more-alarming screams, the team found, though why we respond that way isn’t yet clear.
The study shows that scream communication and the ways in which we understand that vocalization is diverse in humans, compared with other mammals whose screams are usually associated with alarming situations like danger, says Sascha Frühholz, a psychologist at the University of Zurich. His team’s work challenges the dominant view in neuroscience that the human brain is primarily tuned to detect negative threat, he says.
Though the results are limited only to the experiments and don’t reflect how humans would respond to screams in the real world, the rigor of the study methods provides a high confidence in the results, says Adeen Flinker, neuroscientist at New York University’s School of Medicine not involved in the study.
The difference that turned up between alarming and non-alarming screams provides a “deeper understanding of this important vocalization,” says NYU psychologist David Poeppel, who also was not involved in the study. The range of experiments, from acoustic analysis to fMRI, also provides “a nice next stepping stone to develop a more methodical and mechanistic understanding of how we process screams,” he says.