主题：【原创】心理压力---困扰现代社会的恶魔 -- 小炉匠

再贴一个例子,类似试验太多，不翻了：

The experiment places two rats in adjacent cages and differentiates between an "executive" and a "yoked" rat. The "executive" rat is administered a mild electric shock (a low-level, irritating buzzing sensation) which is terminated when the rat presses a lever. The "yoked" rat also receives a shock of equal intensity, but holds no control over the ending of the shock and relies completely on the "executive" rat to stop the shock. Using blood samples, Helmreich then tests hormone levels in areas such as the hypothalamus and thyroid to determine differences in the psychological responses between the two animals.

Helmreich has found that differences do exist both chemically and physically between the two animals. Chemically, a change in thyroid access for the animals causes hormones to be released in different levels, thereby affecting the animals' response. Physically, the "yoked" animal tends to display signs of learned helplessness. Due to its lack of control in a stressful situation, such as the one created by the shock inducement, the "yoked" rat develops difficulties in learning new responses in new situations. Although these reactions may change according to what specific day or situation in which the rat is placed, the "yoked" rats do not generally develop positive reactions to stress and do not effectively learn to deal with new, stressful situations, Helmreich said.