Humans form strong bonds with dogs partly because tactile interaction with them releases calming neurochemicals like oxytocin and serotonin via C tactile fibers.

“So those pictures of monkeys picking around in each other, or people who insist on popping things on one another, or people who go to the hairdresser or the barber and they like touch. It doesn't even have to be massage-- massive oxytocin release. Those data don't get as much play as all the data on”