BALTIMORE — People really can “hear” the sound of silence! The study, conducted by researchers from Johns Hopkins University, used a series of auditory illusions to show that silence is processed in a similar manner to sound. The team’s findings also provided clarity on a longstanding philosophical question — can humans perceive more than just sounds?
The researchers adapted well-established auditory illusions, replacing the original sounds with periods of silence. The result was a fascinating insight into human perception: silence can distort our sense of time much like sounds can. The study convincingly asserts that “nothing is something you can hear”.
One of the illusions utilized in the study involves convincing participants that a sound is longer than it truly is. In the researchers’ adapted version of this illusion, moments of silence seemed longer than their actual duration, mirroring the original sound-based illusion.
The research team suggested that the consistent results between silence-based and sound-based illusions indicate that we perceive silence in the same way we perceive sound. Auditory illusions, similar to optical ones, can manipulate our perception of time, making it seem longer or shorter than it truly is.
An example of this is the “one-is-more” illusion, where a single long beep is perceived as being longer than two short, consecutive beeps, despite both sequences having the same duration. In the study, the research team experimented with this illusion on 1,000 participants, replacing the usual sounds with moments of silence. The outcome mirrored the original illusion, with participants perceiving one long moment of silence as longer than two consecutive, short moments of silence.
“We typically think of our sense of hearing as being concerned with sounds. But silence, whatever it is, is not a sound — it’s the absence of sound,” says lead author Rui Zhe Goh, a Johns Hopkins University graduate student in philosophy and psychology, in a media release. “Surprisingly, what our work suggests is that nothing is also something you can hear.”
The study further found that other auditory illusions, when adapted to silence, yielded similar results. In one experiment, participants listened to soundscapes simulating bustling restaurants, markets, and train stations. They were then asked to identify periods when all sounds abruptly ceased, creating brief moments of silence. The researchers clarified that the objective was not simply to observe that silences could induce illusions, but rather to establish that the same illusions, thought to be exclusive to sounds, worked equally well with silence.
“Philosophers have long debated whether silence is something we can literally perceive, but there hasn’t been a scientific study aimed directly at this question,” says Chaz Firestone, an assistant professor of Psychological and Brain Sciences who directs the Johns Hopkins Perception & Mind Laboratory. “Our approach was to ask whether our brains treat silences the way they treat sounds. If you can get the same illusions with silences as you get with sounds, then that may be evidence that we literally hear silence after all.”
“There’s at least one thing that we hear that isn’t a sound, and that’s the silence that happens when sounds go away,” adds co-author Ian Phillips, a Bloomberg Distinguished Professor of Philosophy and Psychological and Brain Sciences. “The kinds of illusions and effects that look like they are unique to the auditory processing of a sound, we also get them with silences, suggesting we really do hear absences of sound too.”
The findings, published in the Proceedings of the National Academy of Sciences, establish a new way of studying the perception of absence.
Looking forward, the researchers plan to keep exploring the extent to which people hear silence – including whether we hear silences that are not preceded by sound – and also plan to investigate visual disappearances and other examples of things people can perceive as being absent.
South West News Service writer James Gamble contributed to this report.
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