By John BradberryIn 1967, psychologist Martin Seligman and his colleagues at the University of Pennsylvania began a series of experiments subjecting three groups of dogs to a series of shocks. Dogs in Group 1 were simply placed in an experimental area and released without incident. Dogs in Group 2 were subjected to a series of shocks that they could end by pressing a lever. And dogs in Group 3 were presented with repeated shocks over which they had no control. (Word quickly spread among the....