Reach for the hand of a loved one in pain and not only will your breathing and heart rate synchronize with theirs, your brain wave patterns will couple up too, according to a study published this week in the Proceedings of the National Academy of Sciences (PNAS). The study ... also found that the more empathy a comforting partner feels for a partner in pain, the more their brainwaves fall into sync. And the more those brain waves sync, the more the pain goes away. "We have developed a lot of ways to communicate in the modern world and we have fewer physical interactions," said lead author Pavel Goldstein. "This paper illustrates the power and importance of human touch." The study is the latest in a growing body of research exploring a phenomenon known as "interpersonal synchronization," in which people physiologically mirror the people they are with. It is the first to look at brain wave synchronization in the context of pain, and offers new insight into the role brain-to-brain coupling may play in touch-induced analgesia, or healing touch. Goldstein came up with the experiment after, during the delivery of his daughter, he discovered that when he held his wife's hand, it eased her pain. How exactly could coupling of brain activity with an empathetic partner kill pain? More studies are needed to find out, stressed Goldstein. But he and his co-authors offer a few possible explanations. Empathetic touch can make a person feel understood, which in turn -- according to previous studies -- could activate pain-killing reward mechanisms in the brain.