The researchers explain that the acoustic features that seem to communicate fear are also present in excited, happy screams. The bias towards interpreting both categories as fear likely has evolutionary roots.
“The first animal screams were probably in response to an attack by a predator,” Gouzoules says. “In some cases, a sudden, loud, high-pitched sound might startle a predator and allow the prey to escape. It’s an essential, core response. So mistaking a happy scream for a fearful one could be an ancestral carryover bias. If it’s a close call, you’re going to err on the side of fear.”
The authors aimed to test listeners’ ability to decode the emotion underlying a scream based only on its sound. There were 182 participants listening to 30 screams associated with one of the six emotions – anger, pain, happiness, frustration, surprise, and fear. All screams were presented six times but never in sequence. Participants had to rate how likely the scream was associated with each of six of the emotions.
Findings revealed that most often, the participants correctly matched a scream to its emotional context. However, for screams of happiness, participants often rated highly for fear.
The results may help understand why young children often scream while playing. The authors explain that while screams can convey strong emotions, they are not ideal as individual identifiers because they lack the more distinctive and consistent acoustic parameters of an individual’s speaking voice.
“It’s just speculative, but it may be that when children scream with excitement as they play, it serves the evolutionary role of familiarizing a parent to the unique sound of their screams,” Gouzoules says. “The more you hear your child scream in a safe, happy context, the better able you are to identify a scream as belonging to your child, so you will know to respond when you hear it.”