x
SESTOVIC/ISTOCK
SHARE:
Can you hear the sound of silence? It’s a question that may seem better suited to a philosophy class (or a Simon & Garfunkel concert) than a science lab, but a new study published today in the Proceedings of the National Academy of Sciences suggests people really can “hear” the absence of noise. If the finding holds up, it could help researchers better understand the way the human auditory system processes sound, as well as the lack thereof.
“We can certainly appreciate silences, cognitively,” says Ned Block, a philosopher at New York University who wasn’t involved in the work. “But the question of whether we appreciate them perceptually is another matter.”
For decades, auditory scientists, psychologists, and philosophers have debated how the mind responds to the absence of sensory input. But these debates have often been sidelined in favor of learning how our cognitive systems interpret incoming signals from our eyes, ears, and senses, says Anya Farennikova, a philosopher at the University of Amsterdam. “There was a lot of research focusing on perception of objects, like tables, clouds, and trees, but absences were treated as something really abstract. They are treated as something exotic, like a black hole.”
The latest news, commentary, and research, free to your inbox daily
Yet it’s important to understand how we perceive such absences, Farennikova says, because detecting them can help us survive. “When you’re crossing the street, you make sure there are no cars, or if your baby is asleep, you need to monitor the sound coming from the room,” Farennikova says. “So, they’re just as important as present objects.”
To find out how people respond to total silence and whether they can actually perceive it—rather than just infer its presence—an interdisciplinary team at Johns Hopkins University, including psychologist Chaz Firestone and philosopher Ian Phillips, observed how participants responded to a series of auditory and visual illusions.
In the first illusion, known as “one-sound-is-more,” people were asked whether they thought one continuous tone was longer or shorter than two discrete tones separated by a brief silence. (In reality, the two tones with a gap added up to the same duration as the continuous tone.) But people generally said the continuous tone sounded longer than the two discrete tones. When the researchers flipped the illusion, asking participants to gauge the duration of either a continuous silence in the middle of a tone or two discrete silent breaks, they found that the same thing happened: People perceived the continuous silence as longer than the discrete silences.
Another illusion, called the oddball illusion, the researchers presented two sounds simultaneously: an organ playing a sustained note, and an engine running. With both sounds rumbling, suddenly one would stop, resulting in a partial quiet. They did this five times, presenting five such noise dropouts. During the first four dropouts, the organ went silent while the engine kept humming. For the fifth and final silence, the engine noise died while the organ played on. People reported that the last silence seemed longer than the first four, even though they all persisted for the same amount of time.
Together, the findings suggest to the authors and other experts that we perceive these silence-based illusions similarly to sound-based ones. That, in turn, suggests our brains may employ similar mechanisms to process both sounds and silence.
“This is evidence that your mind treats silences as proper input for auditory processing and, in some sense, [as] interchangeable with sounds,” Firestone says.
Nico Orlandi, a philosopher at the University of California, Santa Cruz, agrees. “This gives reason to suppose that silences are treated by the auditory system in the same way sounds are treated.”
Block adds that the researchers have done a good job of eliminating possible confounding factors, such as whether participants were simply distracted by the noise. “It’s a really powerful effect,” he says. (Test it out for yourself here.)
One caveat, Farennikova notes, is that people may experience silence in different ways. For example, some individuals may be replaying sounds in their minds during periods of silence rather than experiencing “true” silence.
