Recent research highlights the surprising activation of vestigial ear muscles during effortful listening, shedding light on the links between our evolutionary past and modern auditory challenges. Though most people associate ear-wiggling with quirky tricks, scientists have uncovered something far more intriguing: our ears still attempt to move subtly when we're straining to pick up sound.
According to the study published on January 31, 2025, led by Andreas Schröer at Saarland University, the auricular muscles, remnants of our ancestors' auditory capabilities, become surprisingly active under demanding listening conditions. While the general usefulness of these muscles has diminished since humans lost the ability to swivel their ears roughly 25 million years ago, evidence suggests they still play a role—albeit indirectly—in our current listening processes.
To explore this phenomenon, researchers recruited 20 participants with normal hearing and used electromyography to measure muscle activity as they listened to audio under varying levels of distraction. Participants tackled auditory tasks with different challenge levels, listening to audiobooks accompanied by competing podcasts. The study categorized the difficulty of these tasks as easy, medium, and difficult, assessing muscle responses during each.
The study revealed intriguing results. The superior auricular muscles, which lift the ear, exhibited increased activity when participants struggled to focus on the target audiobook amid background noise. Interestingly, the posterior auricular muscles, which pull the ear backward, reacted when audio stimuli originated from behind, mimicking behaviors seen in animals like cats and dogs as they shift their ears toward sound sources.
Schröer explained, “These muscles, particularly the superior auricular muscle, exhibit increased activity during effortful listening tasks. This suggests they are engaged not merely as reflexes but potentially as part of our attentional effort mechanisms, especially when dealing with challenging auditory environments.”
Most notable was the correlation between muscle activity and the participants' self-reported listening efforts—participants noted heightened difficulty and increased exertion during the most challenging trials, paralleling the recordings from their auricular muscles. This connection raises the question: could these subtle muscle movements serve as objective measures of listening effort?
While the study's findings are compelling, the practical impact of these muscle movements remains elusive. Schröer cautioned, “The ear movements generated by the signals we have characterized are so minuscule—or even absent—that there is probably no perceivable benefit.” Still, he emphasized the auricle's role in localizing sound, hinting at the outdated yet persistent functionality of our auriculomotor system.
The notion of reactivitating this long-dormant skill also emerged, with some individuals capable of voluntarily moving their ears. Could practice enable more of the population to regain conscious control over these muscles? Future research aims to explore this, potentially unraveling whether our brains can learn to engage these vestigial abilities through training.
Schröer added, “Investigators want to explore the effects of muscle strain itself or the ear's minuscule movements on the transmission of sound.” The study lays groundwork for future inquiries, particularly concerning individuals with hearing impairments. The possibility of developing more effective hearing assessments and aids based on muscle activity presents valuable pathways for enhanced auditory technologies.
These findings contribute to the burgeoning research on vestigial traits—those remnants from evolutionary pasts—such as the appendix and wisdom teeth, which still linger within our biology. They serve as reminders of our evolutionary heritage and the layers of adaptation framing our modern physiology.
While the auricular muscles might not quite serve the purpose they once did, their continued activity during effortful listening offers insights not just about human evolution but also about the subtle, often unnoticed mechanisms still alive within us. Perhaps, even after millions of years of evolution, our biology continues to echo with the whispers of our ancestral past.