Johns Hopkins University researchers have conducted a groundbreaking study that provides evidence that silence can be perceived and heard, just like sounds. This study settles a long-standing debate among philosophers and psychologists regarding whether silence is something that can be truly heard. The findings challenge the conventional notion that hearing is solely concerned with sounds.
Led by Rui Zhe Goh, a graduate student in philosophy and psychology, the team devised experiments using well-known auditory illusions, typically associated with sounds, but replaced the sounds with moments of silence. They discovered that these silence-based illusions elicited the same perceptual effects as their sound-based counterparts, suggesting that the brain treats silence in a manner similar to sounds.
“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,” said Rui Zhe Goh. “Surprisingly, what our work suggests is that nothing is also something you can hear.”
Chaz Firestone, an assistant professor of psychological and brain sciences and the director of the Johns Hopkins Perception & Mind Laboratory, explained, "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."
In one experiment, the researchers transformed the "one-is-more" illusion, where one long beep appears longer than two short consecutive beeps of equal duration, into the "one-silence-is-more" illusion. Astonishingly, participants perceived one long moment of silence as longer than two short moments of silence, replicating the outcome observed with sound-based illusions.
The study involved 1,000 participants who were exposed to various soundscapes simulating environments such as bustling restaurants, markets, and train stations. During the experiments, participants listened for moments of complete silence within these audio tracks. The team found that these silence-based illusions consistently yielded the same temporal distortions as their sound-based counterparts.
Ian Phillips, a Bloomberg Distinguished Professor of Philosophy and Psychological and Brain Sciences, emphasised, "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." He further added, "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."
While the study used silence embedded within soundscapes, further research is planned to explore the extent to which people can perceive silence, including instances where silences are not preceded by sound. The researchers also intend to investigate other forms of absence perception, such as visual disappearances.
This groundbreaking study not only sheds light on the perception of absence but also opens new avenues for understanding how the brain processes and perceives sensory information. Silence, once considered the absence of sound, has now been established as a unique auditory experience that deserves further exploration.
As the sounds of silence continue to captivate the scientific community, researchers at Johns Hopkins University have shown that sometimes, in the absence of sound, there is much more to hear than meets the ear.