With their ears, barn owls can pinpoint the source of a sound with exceptional accuracy, which comes in handy when they are hunting for prey at night. Their special asymmetrical ears are a unique adaptation in the animal kingdom.
Van Wanrooij: ‘Humans are very good at determining where a sound is coming from on a horizontal plane, based on the minute difference in the timing and volume with which a sound reaches one ear compared with the other. If a sound reaches your left ear slightly earlier or louder then the source of that sound is to the left. But we’re also very good at localising sound on a vertical plane. That has to do with the shape of our ears. As a result, sound from above sounds different from sound from below. Our brain is adapted to this.’
With owls, it works differently. One ear is directed more upwards and the other downwards, meaning that differences in loudness vary precisely in the vertical direction.
Barn owl ear moulds
Van Wanrooij and his colleagues wondered what would happen if people were fitted with barn owl ears. ‘This alters the shape of the human ear, making vertical hearing impossible. We were curious to see whether, over time, people would be able to relearn how to hear vertically, despite having a brain that is not, in principle, designed for it.’
To research this, 11 people were fitted with owl ears: rubber earpieces that altered the shape of their ears. They wore these all day for anywhere between 3 and 58 days. ‘That wasn’t necessarily pleasant for those people. Not only is it uncomfortable to have something in your ear all the time, but they also had to answer questions while queuing at the Albert Heijn, for example.'
