When the floor of a partitioned cage is electrified, a dog learns to escape. If the dog is confined while being shocked, it will ultimately cease attempting to escape.
Dogs that were treated to unavoidable electric shocks eventually failed to flee even when it was possible to do so. Furthermore, they displayed several of the characteristics of depression seen in people (lethargy, sluggishness, passivity in the face of stress, and hunger loss).
Seligman (1974) used this to explain sadness in humans as learned helplessness, in which the individual gives up attempting to change their surroundings because they have learned that they are powerless as a result of having no control over what occurs to them.
Although Seligman's account may explain depression to some extent, it fails to take cognitions into account (thoughts).
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