Updated: Apr 10
Humans only have four muscles with which to move their ears. These muscles tend to be weak, and on some people they aren't even functional. Horses however have thirteen muscles that perform a variety of ear movements. Why? Humans communicate their feelings through facial expressions and not by wiggling their ears. But horses display their emotions primarily with their ears, so they need a strong diverse group of muscles to create specific actions and expressions.
Now watching a Western will never be the same!