“…The first group had the ability to avoid the shocks. By pressing a panel with their noses, they could stop the system from delivering shocks. Thus, they could control the situation. The second group received the same shocks but couldn’t influence the outcome. The shocks stopped only when the dogs from the first group pressed the panel. The third group received no shocks at all.” [Seligman, 1977]

So, two groups of dogs experienced the same shocks for the same duration. The only difference was that one group could stop the unpleasant stimulus, while the other group could not, and they learned the futility of their attempts. The third group served as a control group. After this "training," all three groups were placed in a box with a divider they could easily jump over to avoid the shocks. The dogs that could previously control the shocks quickly jumped over the barrier. The control group also easily jumped over the barrier.