You want to condition your dog to salivate to a bell, just like pavlov did. a couple of times a day, you ring a bell, and give your dog a treat. a month later when you ring the bell by itself, your dog doesn't salivate like you predicted he would. what you didn't know is that while you were out of the house, your roommate has been ringing the bell all by itself. your roommate was also randomly giving your dog treats throughout the day. so most of the time the dog heard the bell, there was no food associated with it, and the dog sometimes got food without hearing the bell. the reason the dog didn't condition in this case was because there was a lack of