learned helplessness

A dog in Group 2 would be intentionally subjected to pain by being given electric shocks, which the dog could end by pressing a lever. A Group 3 dog was wired in parallel with a Group 2 dog, receiving shocks of identical intensity and duration, but his lever didn't stop the electric shocks.
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In part two of the Seligman and Maier experiment, these three groups of dogs were tested in a shuttle-box apparatus, in which the dogs could escape electric shocks by jumping over a low partition. For the most part, the Group 3 dogs, who had previously "learned" that nothing they did had any effect on the shocks, simply lay down passively and whined. Even though they could have easily escaped the shocks, the dogs didn't try.
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However, not all of the dogs in Seligman's experiments became helpless. Of the roughly 150 dogs in experiments in the latter half of the 1960s, about one-third did not become helpless, but instead managed to find a way out of the unpleasant situation despite their past experience with it. The corresponding characteristic in humans has been found to correlate highly with optimism.
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One such later experiment, presented by Watson & Ramey (1969), consisted of two groups of human babies... only the group that had already learned about the sensory pillow bothered to use it.

http://en.wikipedia.org/wiki/Learned_helplessness

via turchin