Silence is a ‘sound’ you hear, study suggests – 07/22/2023 – Science

The silence at the end of the musical performance. The pause in a dramatic speech. The silent moment when you turn off the car. What do we hear when we hear nothing? Are we detecting silence? Or are we just hearing nothing and interpreting this absence as silence?

“The Sound of Silence” is a philosophical question that has become one of Simon & Garfunkel’s most enduring songs, but it’s also a subject that can be tested by psychologists. In an article published on the 10th in the journal PNAS (Proceedings of the National Academy of Sciences), researchers used a series of sound illusions to show that people perceive silence as much as they hear sounds. While the study doesn’t offer any insight into how our brains might be processing silence, the results suggest that people perceive silence as its own kind of “sound,” not just an interval between noises.

‘THE VISION THAT WAS PLANTED IN MY BRAIN STILL REMAINS’

Rui Zhe Goh, a graduate student in cognitive science and philosophy at Johns Hopkins University and one of the scientists involved in the study, described a “koan” he likes: “Silence is the experience of the passage of time.” He said he interprets this to mean that silence is “an auditory experience of pure time”.

This idea made him wonder if silence, the absence of sound, is something we really experience, “or is silence just a kind of lack of experience?”

Chaz Firestone, a cognitive scientist at Johns Hopkins and another author of the study, said that if silence “isn’t really a sound, but we can hear it, then evidently there is more to hearing than just sounds.”

But simply saying “Can you hear the silence?” it’s a tough question. So the two researchers, along with philosopher Ian Phillips, asked a different question: Does the mind treat silence the same way it treats sounds?

‘PEOPLE LISTENING WITHOUT LISTENING’

The researchers tested people recruited online with a series of sound illusions. The first test compared a single longer sound with two shorter sounds. The two shorter sounds together add up to the same amount of time as the longer sound. But when people listened to them, they realized that the unique sound lasted longer.

To apply this illusion to silence, Goh and his colleagues reversed the test. The scientists used sounds from restaurants, busy markets, trains or playgrounds and inserted snippets of silence for participants to compare.

They surmised that if people perceive silences as their own kind of sound, then silences must be subject to the same illusion as sounds. A long silence should be perceived as longer than the total of two shorter silences. But if people perceive silence as a lack of sound, the illusion might not exist.

Other tests put silence in different contexts to produce more sonic illusions. In all cases tested, listeners perceived the illusion of a period of silence as longer, just as they would have perceived the illusion of a longer sound.

“When I first heard it, I thought ‘Wow, it works!'” Goh said. Although he ran the tests himself and knew that the periods of silence were exactly the same length, he still had the illusion that one silence was longer than two.

Firestone said that the illusions were as powerful with silences as they were with sounds. “It’s not even like, ‘Oh, it kind of works with silences, but it’s a lot weaker,'” he said. “No, you get the same effect.” In other words, people react to silences the same way they react to sounds, even if they aren’t “hearing” anything.

‘LISTEN TO MY WORDS THAT I MAY’

It would be easy to dismiss the idea that silence has sound, said Sami Yousif, a cognitive scientist at the University of Pennsylvania who was not involved in the study. Sounds are waves that impact ear cells. Not silence. But that doesn’t mean we can’t detect that silence.

The study, Yousif said, shows that “these blank spaces are also a kind of event, they are a kind of unit that is represented in our experience.”

He also appreciated how the researchers used illusions tuned for silence instead of sound. “It’s very clever in the way it takes known phenomena and instead applies them to silences,” he said.

Although the researchers haven’t studied how people’s brains respond to silence, Goh suggested that existing research supports the idea that some neurons and neural processes are involved in the perception of silence.

And knowing that we perceive silence makes silence much… uh… louder: “Silence is a real experience,” said Goh. Perhaps we all pay more attention to the quiet times when we know we can hear the “sounds” of silence.

Translated by Luiz Roberto M. Gonçalves