Watching another person being touched engages the same part of your brain as actual touch, a new study reveals. This, according to researchers, is how we understand what others are feeling -- which means, essentially, that it's the root of human empathy.

Scientists discovered this connection by studying people who experience a kind of extreme empathy, called mirror-touch synesthesia. When those with this condition see another person being touched, their brain is engaged (like most of us) -- but the difference is that they actually feel a tactile sensation -- just as if they had received physical contact.

While the condition is thought to be very rare, doctors say nearly everyone experiences a watered-down version of it when we witness an injury, and flinch. It's thought that by studying this extreme form of a common gut reaction, doctors will be able to understand what causes the emotional component of empathy.