The sound of silence? Johns Hopkins researchers show that people feel it

Researchers at Johns Hopkins University have used auditory illusions to examine how moments of silence can distort people’s perception of time, tackling the age-old philosophical question of whether silence can be perceived as more than the absence of sound.

A team of psychologists and philosophers at Johns Hopkins University used auditory illusions to show that silence distorts people’s perception of time in a similar way to sound. Their findings suggest that we hear silence just as we play, providing a new perspective on how we perceive the absence of stimuli.

Silence may not be deafening, but it is something that can literally be heard, concludes a team of philosophers and psychologists who have used auditory illusions to reveal how moments of silence distort people’s perception of time.

The findings address the debate about whether people can hear more than sounds, which has baffled philosophers for centuries.

We typically think that our sense of hearing is interested in sounds. But silence, whatever it is, is not a sound it is the absence of sound, said lead author Rui Zhe Goh, a philosophy and psychology graduate student at Johns Hopkins University. Surprisingly, what our work suggests is this Nothing it’s also something you can feel.

The research was published July 10 in Proceedings of the National Academy of Sciences.

In this experiment, researchers at Johns Hopkins University replaced silences with sounds in a well-known auditory illusion. The idea was to see if people’s brains treat silences the same way they treat sounds. Credit: Johns Hopkins University

The team adapted well-known auditory illusions to create versions where the sounds of the original illusions were replaced by moments of silence. For example, one illusion made a sound appear to be much longer than it actually was. In the team’s new silence-based illusion, even an equivalent moment of silence seemed longer than it actually was.

The fact that these silence-based illusions produced exactly the same results as their sound-based counterparts suggests that people hear silence just as they hear sounds, the researchers said.

Philosophers have long debated whether silence is something we can literally perceive, but there hasn’t been a scientific study aimed directly at that question, said Chaz Firestone, an assistant professor of brain and psychological sciences who directs the Johns Hopkins Perception & Mind Laboratory. Our approach has been to ask whether our brains treat silences the way they treat sounds. If you can achieve the same illusions with silences that you do with sounds, then it could be proof that we literally hear silence after all.

Like optical illusions that deceive what people see, auditory illusions can cause people to hear longer or shorter periods of time than they actually are. One example is known as the one is more illusion, where one long beep sounds longer than two consecutive short beeps even when the two sequences are equally long.

In tests involving 1,000 participants, the teams swapped the sounds in the one-is-more illusion for moments of silence, reworking the auditory illusion into what they dubbed the one-silence-is-more illusion. They found the same results: People thought one long moment of silence was longer than two short moments of silence. Other illusions of silence have produced the same results as the sound illusions.

Participants were asked to listen to soundscapes that simulated the din of crowded restaurants, markets and train stations. They then listened for periods within those audio tracks where all sounds abruptly cut off, creating short silences. The idea wasn’t simply that these silences caused people to experience illusions, the researchers said. It was that the same illusions that scientists thought could only be triggered with sound worked just as well when sounds were replaced by silences.

There’s at least one thing we hear that isn’t sound, and that’s the silence that occurs when sounds disappear, said coauthor Ian Phillips, Bloomberg Distinguished Professor of Philosophy and Psychological and Brain Sciences. The kinds of illusions and effects that appear to be unique to auditory processing of a sound, we also get with silences, suggesting that we do indeed hear the absences of sound as well.

The findings establish a new way to study the perception of absence, the team said.

The researchers plan to continue exploring the extent to which people hear silence, including whether we hear silences that aren’t preceded by sound. They also plan to investigate visual disappearances and other examples of things people can perceive as absent.

Reference: The perception of silence by Rui Zhe Goh, Ian B. Phillips and Chaz Firestone, July 10, 2023, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2301463120