They put the conditioned dog into a shuttlebox, which consists of a low fence dividing the box into two compartments. The dog can easily see over the fence, and jump over if it wishes. So they rang the bell. Surprisingly, nothing happened! (They were expecting the dog to jump over the fence.) Then, they decided to shock the conditioned dog, and again nothing happened! The dog just pathetically laid there! Hey, what’s going! When they put a normal dog into the shuttlebox, who never experienced inescapable shock, the dog, as expected, immediately jumped over the fence to the other side. Apparently, what the conditioned dog learned in the hammock, was that trying to escape from the shocks is futile. This dog learned to be helpless! This result was opposite to that predicted by B.F. Skinner’s behaviorism, which argued that the dog must have been given a positive reward (like a yummy dog biscuit) to just lie there. (In order to salvage their position, they even went so far as to suggest that the cessation of pain acted as the reward for the dog to sit, but this was not a very good argument. One could alternately argue that when the shock went on while the dog was sitting, it was being punished for sitting. Reminds me of that old joke, “Q: Why did the man pound his thumb with a hammer? A: Because it felt so good to stop.) These observations started a scientific revolution resulting in the displacement of behaviorism by cognitive psychology. What you are thinking, determines your behavior (not only the visible rewards or punishments).