Don't be alarmed by those bone-chilling sounds of terror and anguish coming from the lab of Emory psychologist Harold Gouzoules. He’s harvesting screams.

He gets the sounds from Hollywood movies, TV shows and YouTube videos. His collection includes classic performances by "scream queens" like Jaime Lee Curtis and Fay Wray, along with the screams of non-actors reacting to actual events. "It seems everything these days is recorded and shared," Gouzoules says.

As one of the few scientists researching human screams, he’s amassed an impressive library of high-intensity, visceral sounds. In one of his clips, a woman shrieks in fear as aftershocks from the meteor that exploded over Russia shake a building. Another of his YouTube finds is a little girl’s prolonged, ear-splitting squeal of delight as she opens a Christmas present.

"The ability to belt out a scream is deeply rooted in our evolutionary history, and is no doubt critical to our survival," he says.

Gouzoules first began researching monkey screams, decades ago. He learned that, during fights, rhesus monkeys make particular screams depending on the situation. The different screams communicate to the screamer’s nearby relatives and allies whether it’s a serious fight, requiring their assistance, or just a minor squabble.

More recently, Gouzoules began studying human screams. Study participants come to his "scream lab" and listen to various audio files on a computer, without any visual cues for context. The preliminary results show that participants tend to agree on what sounds should be classified as a scream, as opposed to a moan or a yell. In addition, most participants tend to be good at telling whether different screams come from the same person.

"We’ve also found that people can distinguish different types of screams: A happy scream, a frightened scream, a scream given in pain," Gouzoules says. "Some people are better at this than others. What we found is that these differences correlate with measures of empathy."

Gouzoules has no trouble recruiting study participants. "People find screams inherently interesting," he says. "Most of us live fairly ordinary lives and screaming is not that common. I don’t think that was true evolutionarily – there were lots of things that prompted us to scream."

Despite our fascination with screams, science knows relatively little about them. Gouzoules is honing in on tone, pitch and frequency to try and uncover the hidden patterns and complexities carried in the most intense sounds of human terror, joy and pain.