Ask friends to list the body’s senses, and they will usually stop after five: taste, touch, sight, smell and hearing. Most do not even notice their sixth sense—the sensation of how one’s head is oriented and moving. But losing this capacity can cause dramatic, disabling vertigo, followed by chronic unstead­iness and blurred vision when the head is in motion. Fortunately, good progress is being made toward the development of bionic ear implants to restore balance in people who suffer from damage to the vestibular labyrinth of the inner ear—the part that provides us with our sixth sense.