Why exactly does the Jaws theme send a chill down our spine? What makes Darth Vader's entrance music so unsettling? In short, why does certain music freak us out? Evolutionary biologist Daniel Blumstein thinks he has the answer. Blumstein hit on the idea while observing baby marmots, who would occasionally emit screams when captured, he tells NPR. He came up with a theory: Animals use "nonlinear" noises (defined here as "irregular" and "scratchy") to grab their parents' attention—so we're hard-wired to heed them.
"Clearly, people in Hollywood know this, but it's not as though they're going out and using biologically tested algorithms," Blumstein says. To prove his theory, he had a composer create a set of emotionally neutral scores, and another riddled with nonlinear elements. The results, revealed in the latest edition of Biology Letters, bore out his hypothesis: Volunteers reported higher levels of emotional response, and negative emotion, when confronted with the nonlinear tunes. (Read more scary stories.)