With his coat billowing behind him and his right eye tightly closed, Captain Blackbeard watches the endless sea with his telescope. Suddenly the sea disappears as the pirate opens his right eye. The only thing he sees is his hand holding the telescope. And then, a moment later, the sea is back again. What happened was a change in perception. Our brain usually combines the two slightly divergent images of our eyes into a single consistent perception. However, if the visual information does not match, only one image is seen at a time. This phenomenon is called "binocular rivalry". Researchers have now used this phenomenon to decipher a key mechanism of the brain functions that contributes to conscious visual perception.