Our 15 month old daughter has started hitting about a week ago. It started with our dog. We show her "gentle" with the dog and she gets it initially but eventually will hit him. She will hit us now when we are playing with her. Because of her age, we are not doing time out. We ignore it and distract her or firmly say "no hitting" and put her down or walk away. I have seen this question for 18 months old and up but not 15 months.