Tiny used to bite until I started yelling "Ouch". Now even if we are playing with a toy and he acidentally bites then automatically I'm going "OUCH" and he will stop playing until I tell him " it's OK you just got Mommy finger" I think the ouch thing works...I think they know...When they are really hurting you. Tiny even gets upset when Corey or I fake cry...Like when he won't come and see me...I'll fake cry and he gets all interested in what I'm doing and why! They know...THey know exactly what they are doing!