"Superfluous" muscle helps us to listen with concentration
We humans have some evolutionary remnants that we no longer have any use for. However, the auricular muscles are probably not one of them.
About ten to twenty per cent of people can actively wiggle their ears, powered by tiny muscles. For a long time, scientists assumed that these muscles were just an evolutionary remnant that most of us no longer use. But that was a fallacy. What's more, these auricular muscles are used more frequently than previously thought, reports a team led by Daniel Strauss from Saarland University. According to the study, the muscles are stimulated when we listen intensively or with effort.
Strauss and his team had already discovered in 2020 that auricular muscles become active when we hear interesting sounds whose direction of origin we cannot precisely locate. Depending on the type of sound and its direction, the muscles ensure that our ears change their position, whereby up and down movements as well as rotations forwards or backwards are possible. Only extremely fine Display resolution made it possible to prove this. Previously, it had been thought that auricular muscles were an evolutionary relict that had accompanied humans and other primates for 25 million years. According to the hypothesis, they have long since lost their original function of actively directing the ears towards an acoustic source.
In their new study, Strauss & Co. show that auricular muscles move during intensive listening, for example during a concert or conversation. They tested 20 people with good hearing by playing them three excerpts from audiobooks, with the level of difficulty increasing from time to time. At the same time, skin sensors recorded the electrical activity in the auricles. In the easiest test, a podcast with a male voice was played at a low volume in parallel to the audiobook. At the medium level of difficulty, two quiet podcasts with male and female voices were heard at the same time as the audiobook. Finally, at the highest level of difficulty, both podcasts were played loudly while a female speaker read the audiobook aloud.
The auricular muscles reacted differently to the different test conditions. The posterior muscles, for example, responded to changes in the direction from which the sounds were coming, while the upper muscles adapted to the difficulty of the task. The higher the level of difficulty, the harder the test participants had to listen and the more often they lost the thread. In addition, the more difficult the listening task became, the less accurately they answered questions relating to the book content.
This is hardly surprising, but at the same time it correlated with the activity level of the muscles of the upper auricle: they were not more active in the medium mode than in the easy mode, but were very active at a high level of difficulty. The test subjects had therefore unconsciously tried to orientate their ears towards the audio book. However, it is unclear whether this mechanism actually helps to improve sound perception.
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