'Useless' ear muscles may actually serve a purpose

Did you know that if you can wiggle your ears, you’re exhibiting signs of a past ability that profoundly assisted our distant ancestors in sharpening their sense of hearing?

These muscles, called auricular muscles, alter the shape of the pinna (the ear’s shell). They are considered vestigial, which means that they have become basically useless to humans over the course of evolution.

However, a recent study reveals that even in their limited capacity, auricular muscles spring into action when we are in the middle of sonic chaos, trying to focus on one sound amidst many.

Ear-wiggling muscles

A team at Saarland University has taken a closer look at our seemingly insignificant ear-wiggling muscles.

“There are three large muscles which connect the auricle to the skull and scalp and are important for ear wiggling. These muscles, particularly the superior auricular muscle, exhibit increased activity during effortful listening tasks,” noted Andreas Schröer, the study’s lead scientist.

“This suggests that these muscles are engaged not merely as a reflex but potentially as part of an attentional effort mechanism, especially in challenging auditory environments.”

Listening isn’t as simple as it seems

How do you measure how hard someone is listening? It’s not as straightforward as it seems.

While self-reported measures exist, the key to unraveling this mystery lies in the tool called electromyography, which measures electrical activity in a muscle.

Researchers have previously found that the largest auricular muscles – the posterior and superior ones – show increased activity during attentive listening.

“The exact reason these became vestigial is difficult to tell, as our ancestors lost this ability about 25 million years ago,” explained Schröer.

“One possible explanation could be that the evolutionary pressure to move the ears ceased because we became much more proficient with our visual and vocal systems.”

One of our oldest ear muscles

To investigate the functions of these particular muscles, the researchers assembled a group of 20 study participants with normal hearing.

The participants were subjected to a series of trials where they listened to an audiobook while simultaneously being exposed to distracting podcast sounds.

Conducting trials with varying levels of difficulty, the researchers tracked the electrical activity in the participants’ auricular muscles. Though the trials were designed to be challenging, they were feasible.

After all, if the task was too difficult, participants might give up, and no muscular effort would register on the electromyography readings.

The researchers focused on the participants’ subjective perceptions of effort, their estimated frequency of losing track of the audiobook, and their understanding of the audiobook content.

Distinct responses of ear muscles

The experts discovered distinct responses from the two auricular muscles. The posterior auricular muscle reacted to changes in direction, while the superior auricular muscle responded to the difficulty level of the task.

Participant’s self-reported measures and accuracy in answering questions about the audiobook reflected the task’s difficulty level and correlated with the superior auricular muscles’ activity.

“The ear movements that could be generated by the signals we have recorded are so minuscule that there is probably no perceivable benefit,” explained Schröer.

“However, the auricle itself does contribute to our ability to localize sounds. So, our auriculomotor system probably tries its best after being vestigial for 25 million years, but does not achieve much.”

This new insight into our auricular muscles and their potential role in determining listening effort is a stepping stone towards understanding more about auditory processes.

“Investigating the possible effects of muscle strain itself or the ear’s miniscule movements on the transmission of sound is something we want to do in the future. The effect of these factors in people with hearing impairments would also be interesting to investigate,” Schröer concluded.

Unused ear muscles

If these muscles no longer serve their original purpose, why haven’t they disappeared entirely?

Evolution doesn’t always eliminate unused traits. Instead, they may become repurposed or remain in a diminished state if they pose no significant disadvantage.

While many mammals, including cats and dogs, rely on ear movement to pinpoint sounds, humans have developed other mechanisms – like head-turning and binaural hearing – to achieve similar auditory awareness.

However, the research suggests that these vestigial muscles may not be entirely obsolete.

Future research directions

Even though their movements are nearly imperceptible, the activation of auricular muscles during effortful listening implies they might still make a subtle contribution to sound localization or auditory attention.

Scientists are eager to explore whether these small muscle activations have any measurable impact on hearing precision or cognitive effort, particularly in individuals with hearing impairments.

Future studies may investigate whether targeted training or stimulation of auricular muscles could enhance auditory focus, especially in noisy environments.

Additionally, researchers plan to examine how these muscles function across different age groups and whether their activity diminishes with age, similar to other motor functions.

As technology advances, more refined techniques may help unlock the hidden potential of these long-overlooked muscles, revealing whether they are truly remnants of the past or contribute to our auditory experience.

The full study was published in the journal Frontiers in Neuroscience.

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