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A team of cognitive neuroscientists at the University of Zurich, has found that ancient Aztec "skull whistles" found in gravesites are able to instill fear in modern people. In their , published in the journal Communications Psychology, the group recorded the neural and psychological responses of volunteers as they listened to the screams produced by the whistles.

In digging up ancient Aztec graves dating from the years 1250 to 1521 AD, archaeologists have found many examples of small whistles made of clay and formed into the shape of a skull. These whistles still work today as they did when they were buried next to a person in a grave. They produce most often described as a scream of sorts.

Prior research has shown that the sound is produced by air pushed through different parts of the whistle that then collide. In this new study, the research team sought to uncover the reason behind the creation and use of the whistle.

Anecdotal evidence has suggested that hearing the whistle can lead to a sense of alarm or fear in those in the vicinity; hence its name. To get a more measurable result, the researchers recruited several European volunteers, each of whom were monitored with a device that could measure their neural and psychological responses while they heard the whistle. The researchers also asked the volunteers to describe whatever sensations they were feeling.

The volunteers exhibited similar reactions—certain low-level cortical auditory regions of the brain became instantly activated, indicating that they were on high alert. They also found that the volunteers said the sound made them feel frightened and aversive—they wanted it to stop. The researchers also found that the whistle sound tended to confuse the brain, leaving it reeling momentarily. This, they suggest, hints at the possibility that the whistle was used during ceremonies surrounding the dead, possibly as a way to frighten attendees.