Why do dogs lick humans? It could be a sign of affection.

Between humans, a kiss on the mouth or cheek is a clear signal of warm feelings. There's no single definitive answer, though canine cognition experts have theories. "If we want to distill it down to one thing, it's communication," says Ellen Furlong, an associate professor of psychology and neuroscience at Transylvania University in Kentucky, where she studies dog behavior. Dogs are highly social and well-attuned to humans. If a pup is interacting with you, it's often with purpose.