The hush at the end of the musical performance. The pause in a dramatic speech. The muted moment when you turn off the car. What is it that we hear when we hear nothing at all? Are we detecting silence? Or are we just hearing nothing and interpreting that absence as silence?

The “Sound of Silence” is a philosophical question that made for one of Simon & Garfunkel’s most enduring songs, but it’s also a subject that can be tested by psychologists. In a paper published Monday in the Proceedings of the National Academy of Sciences, researchers used a series of sonic illusions to show that people perceive silences much as they hear sounds. While the study offers no insight into how our brains might be processing silence, the results suggest that people perceive silence as its own type of “sound,” not just as a gap between noises.