My Dobe from 25 years ago I taught to bark as a command because I thought it would be a cute trick. Basically just taught it through frustration. I put her on the porch with a screen door and from the inside I repeated "Bark!" really excitedly, and would jump around and act silly. She would start running around and of course want to join me, but the door was there and she finally made a little bark in frustration - I swung the door open and we had a party. Then rinse & repeat, didn't take but a few times and she soon knew the bark command. She was not a natural barker at all. She barked at squirrels and that's about it. Total sweetheart. This one I have now has been barking at something or everything since about 3 months old and I can't make it stop.