The muscles that permit modern humans to flex their ears likely fulfilled a more vital role for our evolutionary predecessors.(Image credit: Khmelyuk/Getty Images)ShareShare by:
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A fresh study has discovered that the small muscles that allow individuals to wiggle their ears involuntarily contract when we’re attempting to single out a specific sound amidst background clamor.
Consider how felines, canines, and some primates move their ears in reaction to unfamiliar sounds. This natural movement is not just for show; it serves to direct sound towards the animals’ eardrums, thereby improving their capacity to precisely locate and interpret sounds.
Current investigation at Saarland University in Germany has demonstrated that humans also shift their ears in response to auditory input — at least to a certain extent. For instance, when we make an effort to discern what someone is saying in a boisterous environment, tiny muscles in our external ears, recognized as the superior auricular muscles, activate, likely in an attempt to enhance our auditory perception. Nevertheless, because the muscle is diminutive, it probably exerts a minimal influence on our capacity to hear.
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Now, expanding on their prior work, the researchers at Saarland University have carried out another investigation, documented Jan. 31 in the journal Frontiers in Neuroscience, to scrutinize further the response of the superior auricular muscle when individuals struggle to hear. They believe this research could have functional uses in refining assistive hearing technology down the line.
A vestige from our forebears
While the auricular muscles in contemporary humans are diminutive and feeble, in our remote predecessors, these muscles potentially moved the ears to and fro, thereby optimizing hearing by more successfully capturing sound. Some individuals can still voluntarily wiggle their ears, but nonetheless, these muscles are regarded as “vestigial” — evolutionary relics with minimal practical function at present.
Having said that, the scientists involved in the new study ponder whether the muscles might prove beneficial for hearing-aid technology in the future. A possible application is the incorporation of artificial intelligence that is capable of perceiving and deciphering muscular movements.
“If the superior auricular muscles, those that perk the ears up, are activated, the hearing aid would know that the user is expending a lot of effort to hear and understand something,” study co-author Steven Hackley, a researcher at the University of Missouri, mentioned to Live Science in an email. “The hearing aid would then boost the sound level for sounds coming from that direction,” Hackley posited.
To discover more regarding these small ear muscles, Hackley and his team enrolled 20 participants possessing typical hearing and affixed electrodes to their scalp to monitor electrical activity in their superior and posterior auricular muscles, which are situated above and behind the ears respectively.
While seated in a soundproof chamber with their heads immobilized by a chin rest to avert movement, the participants listened to an audiobook while a distracting podcast played concurrently. These sounds originated from speakers placed either in front of or behind the participants.
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The participants finished 12 five-minute iterations of this experiment, each set at one of three challenge grades: low, medium or high. At the simplest grade, the audiobook stood apart from the podcast with a reasonable volume and unique sound, rendering it significantly simpler to concentrate on. However, as the challenge escalated, the podcasts were amplified and adopted a comparable pitch to the audiobook. This alteration made it more demanding, though not unattainable, for participants to focus on the audiobook.
Based on the electrode data, the scientists observed that when sounds came from behind the participants, their posterior auricular muscles became more active compared to when the sounds were emitted directly in front of them. The researchers suggested this reflex might be a now-vestigial trait that at one time assisted our forebears in detecting sounds originating from outside their range of sight.
In contrast, the activity of the superior auricular muscles was not affected by the direction of the sound. But as the listening challenge became more intense, these muscles showed greater activity. The study authors surmised that the activity of the superior auricular muscles is related to listening effort, reflecting how intensely someone is purposefully striving to hear. However, other specialists voiced reservations in interpreting the outcomes.
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“I am not totally comfortable drawing that conclusion,” Matthew Winn, a researcher at the University of Minnesota who was not involved in the study, told Live Science in an email. “The response might instead reflect arousal or noise frustration, which is a thing that “happens to you,” as opposed to listening effort, which is a thing that you decide to bring to a situation,” he suggested. “Arousal,” in this context, refers to a state of heightened state of alertness, or responsiveness to sound.
Does this heightened muscle activity assist modern humans in hearing more effectively? Most likely not.
“The ear movements that we have been studying are probably too tiny to have any effect on hearing,” Hackley said. “We call them “micro-movements” because they usually are less than a millimeter or two [less than one-tenth of an inch].”
Nonetheless, Hackley hopes these findings will translate into practical applications in the future, perhaps to augment hearing aids.
Clarissa BrincatLive Science Contributor
Clarissa Brincat is a freelance writer specializing in health and medical research. After completing an MSc in chemistry, she realized she would rather write about science than do it. She learned how to edit scientific papers in a stint as a chemistry copyeditor, before moving on to a medical writer role at a healthcare company. Writing for doctors and experts has its rewards, but Clarissa wanted to communicate with a wider audience, which naturally led her to freelance health and science writing. Her work has also appeared in Medscape, HealthCentral and Medical News Today.
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