Puppies quickly learn that they get a reaction when they bite, whether it’s from their littermates or from their human caregivers. It hurts! Teaching your new puppy the importance of a gentle mouth is an important lesson. When your puppy clamps down on your hand too hard, mark the painful infraction by saying “Ouch!” and pull your hand away. Withdraw your attention for a few moments, and then resume contact with your dog. If your puppy bites down too hard again, mark the bite by saying “ouch” again, but this time get up and walk away from your dog, leaving him alone. This is social isolation, a potent but gentle punishment. If your timing is good, your puppy will soon learn that biting too hard makes his favorite person leave.