"Tricking Your Ears" on today's Moment of Science.
Recently, researchers have theorized that the brain has to learn the shape of its own ears in order to hear correctly. In order to further research this theory, they've developed the plastic pinna mold. Pinnas are the distinctive ridges in your outer ear; everyone has slight differences in the shape of their pinna.
When place inside the ear, these pinna molds give you new pinnas, effectively changing the shape of your outer ear. Researchers have theorized that the brain has to learn the shape of its own ears in order to hear correctly. Since everyone's pinnas are different, everyone's ears channel sound waves a little differently.
The brain should have to learn the shape of its own ears. By temporarily altering the shape of the pinnas with plastic molds, researchers in the Netherlands found that indeed, people with new pinnas had a hard time locating sound sources. After a few weeks of wearing the molds, however, their brains learned the new shapes of their ears and adjusted accordingly.
After taking the molds off, volunteers had no trouble readjusting. It seems that the brain remembered the shape of its real ears and didn't have to relearn it.