afferent

But our skin also has sensors known as C-tactile fibers or afferents that are specifically sensitive to social touch from people and the caress of a loved one.

Fairhurst, for instance, wears more perfume and spends longer washing her hair – “a direct activation” of her C-tactile afferent nerves, she thinks.

These fibers, known as “C-tactile afferents” and found on places such as the forearm or back, transmit messages directly and slowly to the central nervous system.

Stroking the forearm, rich in type C afferents, lit up social brain areas in the controls, but stroking the palm, which contains predominantly type A nerve fibers, had no such effect.

C-tactile afferents are “beautifully, exquisitely evolved,” McGlone says, and without the touch that they respond to, babies have weaker neural responses and longer hospital stays and do not gain as much weight.