We have mirror neurons in our brain that fire in synchronicity with what we are observing in others. If you watch someone running, the parts of your brain that would make you run light up with neural activity. Watch the spectators at a wresting match, and you see people writhing in their seats trying to escape from the hold that is being applied out on the mat.
The mid-brain allows us to communicate and share feelings. Mammals, and to some extent birds as well, bond with one another through broadcasting and receiving one another on this emotional bandwidth.
In a paper published in Science in 2004, researches took fMRI brain scans of 16 romantically involved couples. The experiment involved giving an electric shock to a subject and observing the parts of the brain that registered activity during their reaction. They found that the same area lit up if they simply told the subject when and how strong the next shock would be. When they gave the other partner a shock as well, the brains of both parties lit up in essentially identical ways.
The research proves that whether we are anticipating our own pain or empathizing with another we are having substantively the same experience. In other words, we literally do feel one another’s pain.