Seligman, Martin E. (1975). Helplessness: on depression, development, and death. San Francisco: Freeman.
Seligman
discovered learned helplessness almost by accident when he created a
conditioned learning experiment based on Pavlov’s model. In Pavlov’s well-known experiment, dogs learned to associate a conditioned stimulus (a bell) with an unconditioned stimulus (food) and exhibited a conditioned
response (saliva) to the sound of the bell before the food appeared. Seligman placed dogs in a harness where they heard a tone (conditioned stimulus) and then received shocks which they could not escape or alter by their response, an unconditioned stimulus with no conditioned response. The next day, the dogs were placed in a box with a barrier. The tone was followed by a shock as before, but this time the dogs could escape the shock by jumping the barrier, or could avoid it entirely if they crossed quickly enough in response to the tone (conditioned response). To Seligman’s surprise, the dogs did not jump the barrier. By contrast, dogs that were not shocked in harness had no difficulty in learning the conditioned response.
Learned helplessness, as this phenomenon is called, has been demonstrated in many species, including humans. To explore the process by which it develops, Seligman employed a “triadic” design with three groups of animals. Animals in one group were able to stop the shock with a conditioned response. They were “yoked” to animals in a second group. These received the same shocks as their companions in the first group, but could not control it. A third group was harnessed but received no shocks. Only those in the uncontrollable shock condition were subsequently unable to learn a conditioned response, having learned in the previous phase that no action on their part would bring relief.