What would it be like if you went to a cocktail party – or a rock concert or even your quiet corner coffee joint, for that matter – and you didn’t have the ability to filter out one voice or sound from the sea of other sounds around you? This ability is called “selective hearing” and is a computational function in your brain that enables you to focus in on your companion’s voice in the midst of the endless sound waves coming from ceiling fans, ambient music, and other people’s voices bouncing off the walls. Your ability to focus in on that single selected voice is impressive.
Doctoral candidate Bridget Queenan of Georgetown University Medical Center is figuring out how we humans are able to perform this difficult feat by studying bats. She has found that certain neurons in bats’ brains can “quiet” other neurons, allowing the bat to prioritize certain sounds over others. In short, through “turning up the volume” on certain neurons, bats can zero in on the most important sounds, such as their own echolocation sounds, and allow other sounds to fade into the background. (2010)
Researchers at UCSF recently published an article in the journal Nature that describes how they have actually seen this process take place in humans. Using a sheet of 256 electrodes placed on the brain, they can see which neurons activate at the sound of certain voices through the use of sound samples played simultaneously. They could then “decode” the data from the electrodes to find out what the patient heard without talking to the patients themselves. (2012)
When you consider that a bat must hunt, gather, and navigate through spaces populated with thousands and thousands of other bats, it’s easy to see why a brain function like selective hearing is essential to survival. Humans have depended on selective hearing throughout our history for much the same reason.
Although most modern humans are no longer engaged in hunting and gathering activities, our world would look very different were it not for selective hearing. Imagine living in a city – or even a moderately sized suburban town, for that matter – with its ambient atmosphere combining traffic, voices, weather sounds such as wind or rain, and the rest of the cacophony of daily life that we simply don’t think about from moment to moment. Were it not for selective hearing, we would drown in an overwhelming sea of noise, unable to focus on any one sound well enough to effectively evaluate its importance. Considered in that context, the neurological capability that we call selective hearing has played a significant role in defining how we function as a species.
You can also see how this ability would be important in the real-world context of the classroom. Without it, students who are already easily distracted would simply be swallowed by the noise. Independent research has shown that students’ selective auditory attention improves after they use the Fast ForWord program for as little as six weeks. (2008)
So the next time you find yourself unable to focus on someone’s voice at a party, or you encounter a student who is having a hard time paying attention in a noisy classroom, take a moment. Appreciate your ability to use your selective hearing. And have patience while that other person works to engage theirs.
Bardi, J. (2012). How Selective Hearing Works In the Brain. Retrieved from the University of California San Franciso website: http://www.ucsf.edu/news/2012/04/11868/how-selective-hearing-works-brain.
Mallet, K. (2010). Bat Brains Offer Clues As to How We Focus on Some Sounds and Not Others. Retrieved from the Georgetown University Medical Center: http://explore.georgetown.edu/news/?ID=54075&PageTemplateID=295.
Stevens,C., Fanning, J., Coch, D., Sanders, L., & Neville, H. (2008). Neural mechanisms of selective audiory attention are enhanced by computerized training: Electrophysiological evidence from language-impaired and typically developing children. Brain Research. 1205, 55 – 69. doi: 10.1016/j.brainres.2007.10.108.
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