However, these sounds are inevitably punctuated by silent pauses that mark the absence of acoustic waves. In fact, silence is an integral part of our everyday experience, and the expression “deafening silence” is a good example. But how the human brain perceives this absence of noise has never been fully understood.
In a study published on July 10 in the journal Proceedings of the National Academy of Sciences, a research team from Johns Hopkins University in the USA carried out an experiment showing that our brains actively perceive silence in the same way as they hear sound. “Silence of any kind is not sound. It is the absence of sound.
To find out how people react to absolute silence and whether they can actually perceive it, rather than inferring its presence, the scientists observed how participants responded to a series of auditory illusions.
In the first experiment, known as “one-sound-is-more”, the team asked participants whether they thought a continuous sound was longer or shorter than two discrete sounds separated by a brief silence. Overall, the two sounds lasted exactly the same length of time, in reality. But respondents generally said that the continuous sound seemed longer than the two discrete sounds.
The same researchers did this five times. For the first four interruptions, the organ fell silent while the engine continued to hum. For the fifth, the engine noise died away while the organ continued to play. Participants reported that the last silence seemed longer than the first four, although they all lasted the same amount of time. The results of these experiments suggest that our minds do not infer the absence of noise, but actually perceive it. According to the study’s authors, these results suggest that our brains use similar mechanisms to process sound and silence.
“This is evidence that our mind treats silences as appropriate data for auditory processing and, in a certain sense, as interchangeable with sounds,” Chaz Firestone points out to our Science colleagues. If this discovery is confirmed, it could help researchers to better understand how the human auditory system processes sound, as well as their absence. The team of scientists indicates in the study report that they will continue their research into the absence of visual or tactile stimuli, so as to better understand how the brain deals with the absence of sensory stimuli and how we can perceive things that aren’t there. A sixth sense?