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Stress-Induced Behavior

Mild stress produces a state of activation that can affect virtually any behavior (Antelman & Caggiula, 1980). Note the word mild. The ideal way to create mild stress in a rat is to pinch its tail gently. The tail-pinch is not painful. If you make a tail-pinch painful by increasing its intensity, the rat's behavior becomes disorganized. Under extreme stress, animals are not activated; they may "freeze." However, given a mild tail pinch, a rat becomes activated. After a tail-pinch, a rat with access to food and water will start eating or drinking within a few seconds, even if it is full. Rats can be made obese this way, suggesting an analogy to stress-induced eating in humans.

How can stress produce a motivational state similar to Hullian drive?

Stress-induced behavior can involve virtually any behavior. A tail-pinched female rat will mother babies, if babies are present. If another rat is present, it may attack the other rat. Classical conditioning occurs faster and is remembered longer after a low-intensity tail shock (Shors, Weiss, & Thompson, 1992). The activation caused by mild stress has these effects in rats:

A mild tail-pinch to a rat has what effect?

1. If babies are present, they are mothered

2. If a rival is present, it is attacked

3. If a mate is present, sexual activity is initiated

4. If there is a threat, defense responses are activated

5. If a pest is present, it is threatened

6. If food is present, it is eaten

7. If water is present, it is drunk

How does this resurrect one of Hull's concepts?

The concept of stress-induced behavior appears to resurrect one of Hull's main concepts (actually one he borrowed from earlier psychologists): that of a drive state in which all behaviors are activated. Apparently mild stress acts like Hullian drive. Students should be able to believe that. Under the mild stress of an approaching examination or term paper deadline, previously impossible behaviors are suddenly activated.

What is "motivational arousal"?

Is the tail-pinch somehow unique as a stressor? Apparently it is not. Antelman and Caggiula (1980) cite studies showing that any form of stress seems to make any behavior more likely, with the behavior depending on context. Brehm and Self (1989) refer to this concept as motivational arousal. Motivational arousal, they say, is increased by needs and mild stresses of all types. For example, in humans, the expectation that a task will be difficult increases motivational arousal.

The exact form of behavior resulting from stress depends on the individual and the situation. If you eat when you are stressed, it is stress-induced eating. If you fight, it is stress-induced aggression. If you are a human who channels stress into constructive activity, you may seem uncommonly motivated or "driven" when influenced by mild stress.

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