Читать книгу Demystifying Research for Medical and Healthcare Students - John L. Anderson - Страница 38

Martin Seligman is one of my psychology heroes. In his early research, he was doing some experiments involving Pavlovian conditioning in dogs. These involved restraining dogs in a ‘Pavlovian hammock’ and giving them conditioning in which tones (sounds) were followed by electric shocks which were painful but not damaging. These shocks could not be avoided – no matter what the dog did. They were inescapable – uncontrollable. Afterwards the dogs were put in a ‘shuttle box’ (Figure 2.5). This was a large box divided into two sections with a dog‐shoulder high barrier in the middle. The floor had a grid which could be electrified on either or both sides. Seligman (1975) eloquently describes his initial results.

When placed in a shuttle box, an experimentally naïve dog, at the onset of the first electric shock, runs frantically about until it accidentally scrambles over the barrier and escapes the shock. On the next trial, the dog, running frantically, crosses the barrier more quickly than on the preceding trial; within a few trials it becomes very efficient at escaping, and soon learns to avoid shock altogether. After about fifty trials the dog becomes nonchalant and stands in front of the barrier; at the onset of the signal for shock it leaps gracefully across and never gets shocked again.

A dog that had first been given inescapable shock showed a strikingly different pattern. This dog's first reactions to shock in the shuttle box were much the same as of a naïve dog; it ran about frantically for about thirty seconds. But then it stopped moving; to our surprise, it lay down and quietly whined. After one minute of this we turned the shock off; the dog had failed to cross the barrier and had not escaped from shock. On the next trial, the dog did it again; at first it struggled a bit, and then, after a few seconds, it seemed to give up and to accept the shock passively. On all succeeding trials, the dog failed to escape. This is the paradigmatic learned‐helplessness finding. (Seligman, 1975).

FIGURE 2.5 Shuttlebox design.

Seligman demonstrated from this and later work on human subject that learned helplessness saps the motivation to initiate responses; disrupts the ability to learn; and produces emotional disturbance. That is, it has three levels of effect:

 motivational

 cognitive

 emotional.

He went on to show how this effected people in real life and that this could even be implicated in depression and death. Read his book Learned Helplessness: On Depression, Development, and Death (1975); in addition to being educational, it is a thoroughly good read!

Don Hiroto (Hiroto 1974; Hiroto and Seligman 1974) worked on learned helplessness research in humans – using the universally accepted subjects: university students. Now, you can't put humans into shuttle‐boxes, they are too unwieldy and dangerous. But they designed a ‘finger shuttle box’. This was a small box with two compartments into which the research subject could insert her/his finger. There was a low barrier in the middle and the subjects could move their fingers from one side to the other. Another approach was to use a four‐button board. This was a simple board with four buttons, a green light (to indicate success), and a red light (to indicate failure). Pushing any button four times made the noise stop immediately in the ‘control’ group, but not if they were in the ‘helpless’ group when no amount of button pushing could stop the noise. He used a triadic design – with subjects being randomly assigned to one of three groups. An escape group were given loud noise which could be turned off by pushing a button. A yoked group got the same loud noise as the escape group, but they had no control over it. The third group got no noise. Subjects in a yoked group are linked to the subjects in the experimental group, but have no control over the stimuli they are given. Next, all were taken to a finger shuttle box and were exposed to loud noise. They could escape the noise by moving their finger from one compartment of the box to the other. The escape group and the no‐noise groups easily learned to escape the noise by ‘shuttling’ their fingers. The yoked group, however, failed to escape and avoid the noise: ‘Most sat passively and accepted the adverse noise’.

Note the sophistication of this design. Both the experimental group and the yoked group got exactly the same amount of the stressor (noise). The only difference was that the experimental group could control the situation – the yoked group could not. And the control group were not exposed to the stressor at all. Thus, any differences between the experimental group and the yoked control group could not be attributed to different exposures to the stressor. And the no‐noise control group acted as a group who received no stressor – that is, they acted as a group to check for any Hawthorne Effect!