We think of our sense perceptions as a constant inward flow, like a video feed. But recent research finds that in actuality, it operates on a different model, one more akin to a strobe light. More precisely, our hearing and vision are rhythmic pulsations taking place inside the brain.
“Recent evidence suggests that ongoing brain oscillations may be instrumental in binding and integrating multi-sensory signals,” the authors of this latest study write. Previous work proved that vision works this way. Now, researchers at the University of Sydney in Australia, along with Italian colleagues, discovered that hearing does as well. Their results were published in the journal Current Biology.
When we survey a scene, the brain doesn’t pay attention to everything all at once. If it did, our ancestors wouldn’t have made it very far. They’d have been gobbled up by predators in no time, as they'd be constantly overwhelmed by sensory overload. Instead, the brain prioritizes certain things over others, mostly opportunities and threats. This helped our early ancestors survive and thrive, since it allowed us to reserve limited cognitive energy, by concentrating on what’s important.
Auditory oscillations occur in patterns similar to vision. Credit: Getty Images.
Oscillation reserves brain resources, allowing for concentration to come in protracted periods. The strobing aspect allows the brain to weave together all the relevant data points, which are then put into a narrative arc, a format that's easily understood and explainable to others. The results of these findings may help us better understand how humans perceive and interact with our environment and even the subtleties surrounding our decision-making process.
According to a University of Sydney press release, the most important findings are:
1. Auditory perception oscillates over time and peak perception alternates between the ears – which is important for locating events in the environment;
2. Auditory decision-making also oscillates; and
3. Oscillations are a general feature of perception, not specific to vision.
Researchers chose a simple task. Volunteers had to identify a noise. 20 participants took part. Each underwent 2,100 separate tests. The scientists monitored participants’ brains while they did so. What researchers found was that we switch from one ear to another when trying to identify a sound.
First, one ear increases in sensitivity until it reaches its peak. Then as the sensitivity in that ear declines, that of the other increases. It goes back and forth like this until the sound is identified. Yet, the mechanism occurs so fast, we aren’t aware of it. Six auditory cycles occur each second. Though this sounds impressive, consider that brain fluctuations at their fastest oscillate 100 times per second.
The quickest brain oscillations occur in 100th of a second. Credit: geralt, Pixababy.
What’s interesting in that the human decision-making process takes place at the same rate as sound oscillations, in just one-sixth of a second. No one is sure why. One theory is that the sensory rhythms coincide with attention patterns. These researchers will look next into the sense of touch, to see if it too oscillates in a similar pattern. Scientists believe the paradigm exists across all our senses.
According to Professor David Alais, a researcher on the study, “The brain is such a complex ‘machine’ one could say – it is a testament to science that we are starting to make sense of it – but a takeaway could be that there is so much we don’t know.” He added, “A decade ago, no one would have thought that perception is constantly strobing – flickering like an old silent movie."
Although it’s been known for years that vision works this way inside our brain, this is the first time it’s been proven that hearing does as well. According to Prof. Alais, “These findings that auditory perception also goes through peaks and troughs supports the theory that perception is not passive but in fact our understanding of the world goes through cycles.”
To learn more about auditory processing, click here: