The skin is our gateway to the physical world. Below its surface are oodles of nerve fibers relaying different types of messages to the brain. At the ends of the fingertips, for example, fat and fast Aβ nerves help you fish for keys at the bottom of a messy purse, or feel the difference between cotton and polyester. Nearby those big nerves are thinner and slower C-fiber nociceptors, which transmit pain, and others that relay itchiness.

What I didn’t know until this week is that there is yet another type of nerve, found only under hairy skin, that carries information about our social interactions. These nerves, known as C-tactile (CT) afferents, respond to slow, gentle stroking — the soft touch you’d