In the same way that rabbits, dogs, cats or horses, humans prick our ears when we perceive an interesting sound or noise, or at least we try to do it even if we are not aware of it. In fact, the movements are so subtle that they are not visible to the naked eye, although they can be detected by recording the activity of the muscles around the ears. A team from the Saarland University describe on eLife how they have reached this finding.

As they explain, they not only examined the muscular activity of the participants, but also filmed the movement of their respective ears. They found that each time the subjects heard an unexpected sound or were asked to focus on one of two sound sources, they showed muscular activity in the ears. Analysis of the images showed that the muscles moved the pinna according to the type of sound and its direction, both upwards and backwards. The researchers interpret this manifestation as an attempt at directional movement.

Vestigial system

The authors note that this “neural fossil” has accompanied humans and other primates for about 25 million years. It is unknown why both of them lost the ability to align the atria with sounds. In any case, they indicate, there is a vestige of that orientation system.

Daniel Strauss, lead author of the study, states in a press release that the results of this study could have practical use, for example, to develop more refined hearing aids. In general, people who use a hearing aid today have difficulty distinguishing between sounds that occur simultaneously. Movement of the ear muscles may be helpful: The hearing aid may align the directional microphones on the device in the proper direction.

Jan Dönges

Reference: “Vestigial auriculomotor activity indicates the direction of auditory attention in humans”. Daniel J. Strauss et al. published online in eLife, July 2020.