Studying the way an animal moves by looking at its ears might seem like a poorly thought-out strategy. After all, short of watching it directly, most biologists would choose to look at more obvious traits like tracks, or limb bones.

But while an animal’s limbs may drive it forward, its inner ear makes sure that it doesn’t immediately fall over. By controlling balance, it plays a key role in movement, and its relative size can tell us about how agile an animal is.

When we walk, the image that forms on our retinas changes quite considerably. But no matter how fast or erratically we move, our view of the world neither jerks nor judders. It’s all stable images and smooth transitions,