That is fascinating, Spur, thank you for that. We have to leave our dogs occasionally to work conventions and we leave alternating bark shock collars/citrus spray collars to keep ours from barking too much. Neighbors were complaining they were barking all night when we were gone and we try to be good neighbors. The collars work, but make me feel badly. Your information has cheered me up on their use. Other dogs we have had in the past were more discriminatory barkers, it's only been the last couple of years we had to make this change. I do believe in negative reinforcement as well as positive reinforcement too though. It would be a wonderful world if positive reinforcement always worked like a dream, but as a realist I know it doesn't.