While most animals only scream when attacked, humans express a variety of emotions through screams.

There are few sounds more attention-grabbing than a scream. Humans scream for several reasons, and we are surprisingly good at understanding what a scream means.

A new study from researchers at Emory University in Atlanta, GA, explores this capability and finds there is one significant exception, however.

People will likely mistake a person’s scream of happiness for a scream of fear.

The basic reason for screaming

Most animals who scream only do so when being attacked. However, nonhuman primates also use screams to call for help when threatened, said Prof. Gouzoules: “Their kin and friends will come to help, even if some distance away, when they can recognize the vocalizer.”

Even so, Prof. Gouzoules suggests that our mistaking happiness in a scream for fear may have something to do with the original reason for screaming.

“The first animal screams were probably in response to an attack by a predator. In some cases, a sudden, loud, and 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 is a close call, you are going to err on the side of fear,” he notes.

Given this, Prof. Gouzoules wonders if there is an evolutionary advantage in how human children scream so often in play.

“Nobody has really studied why young children tend to scream frequently,” he said, “even when they are happily playing, but every parent knows that they do. It’s a fascinating phenomenon.”

Prof. Gouzoules continued: “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.

“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,” he adds.

Screaming meanings

Prof. Gouzoules’ lab has been collecting recorded screams for some time from movies, TV shows, and YouTube videos.

These include screams from actors in horror movies as well as the unrehearsed cries of ordinary people responding to actual events in their lives.

The researchers have identified the screaming timbres and pitches that have associations with different emotions.

According to the study authors, the emotions that screams can successfully express are anger, frustration, pain, surprise, fear, and happiness.

For the study, the researchers selected 30 recordings from 26 different vocalizers. The team chose recordings based on their sound quality, for example, minimal noise or no overlapping sounds, and their ability to convey emotion.

Most of the 22 screams were from women, with only eight being from men. The authors explain that this “was the consequence of our goal to include an ample number of screams from happy emotional contexts, which proved difficult to find for males (an observation we suggest is noteworthy).”

The researchers recruited 182 participants from Emory University — 124 female and 58 male — to listen to the recordings and identify the emotion each scream conveyed. Each was played six times during the test, although not in an established sequence.

Researchers asked the individuals to rate from 1 to 5 how strongly they agreed with a statement identifying an emotion expressed by the scream.

“To a large extent, the study participants were quite good at judging the original context of a scream, simply by listening to it through headphones without any visual cues. But when participants listened to screams of excited happiness, they tended to judge the emotion as fear. That’s an interesting, surprising finding.”

– Prof. Harold Gouzoules

Prof. Gouzoules also notes that there are certain human activities in which happiness and fear go hand-in-hand. “In fact, people pay good money to ride rollercoasters, where their screams no doubt reflect a blend of those two emotions,” he observed.

The study researchers also note that some aspects of nonverbal communication could be the precursors of spoken language.

They conclude that this is why the diversity of screams might have evolved partly through coevolution with spoken language.

Medical reference: Medical News Today