DISTORTED, spiky music has an effect similar to that of animal distress calls, scientists say.
The theory may explain how Jimi Hendrix's wailing guitar excited a generation in 1969, or the chilling impact of the soundtrack to the film Psycho.
A team of US experts believe our response to such music mirrors the way animals react to sounds of distress.
"Music that shares aural characteristics with vocalisations of distressed animals captures human attention and is uniquely arousing," said Dr Daniel Blumstein, of the University of California at Los Angeles (UCLA).
Dr Blumstein, an expert on animal distress calls, set out to test the theory with the help of two musicians. One, Peter Kaye, is a Californian movie and TV score composer. The other, Dr Greg Bryant, is an assistant professor of communication studies at UCLA.
Together Kaye and Bryant composed a series of original 10 second synthesiser pieces designed to have specific effects on listeners' feelings.
One, likened to "elevator music" and designed to be emotionally neutral, lacked noise or abrupt changes in frequency or pitch.
Another began in a similar easy-listening manner but then suddenly broke into Hendrix-style distortion.
Students were asked to listen to the musical sound-bites and rate them according to how arousing, positive or negative they felt.
When the music featured distortion, the volunteers rated it as more exciting, the scientists reported in the Royal Society journal Biology Letters.
They were also more likely to describe it being charged with negative emotion.
Animals crying in distress commonly distort their voices. One of the best known examples is the "scream" of a rabbit facing death, said Dr Bryant.
"This study helps explain why the distortion of rock 'n' roll gets people excited; it brings out the animal in us," he said.
Next the researchers plan to test how different types of music affect the nervous system.