71.Perry Jones might be      .

A.Gala’s classmate

B.a person in charge of Stuyvesant High School

C.Gaia’s teacher

D.a person in charge of Lauder Exchange Program

E

We sometimes think humans are the only species which can bear anxiety, but stress seems to affect the immune(免疫)system of lower animals too. In one experiment, for example, behavioral scientist Mark Lauden, at the University of Denver, gave mild electric shocks to 24 rats. Half of the animals could turn off the electricity by turning a wheel in their cage, while the other half could not. The rats in the two groups were paired so that each time one rat turned the wheel it protected both itself and its helpless partner from the shock. Lauden found that the immune reaction was below normal in the helpless rats but not in those that could turn off the electricity. What he has proved is that lack of control over an event, not the experience itself, is what weakens the immune system.

Other researchers agree. Jay Weiss, a scientist at Duke University School of Medicine, has shown that animals who are allowed to control unpleasant stimuli(刺激)don’t develop sleep disorder or changes in brain chemistry of stressed rats. But if the animals are faced with situations they have no control over, they later behave passively when faced with experiences they can control. Such findings make researchers believe that the experience or feeling of helplessness is one of the most harmful factors in stress.

One of the most surprising examples of how the mind can change the immune reaction was discovered by chance. In 1995 Robert Ader at the University of Rochester School of Medicine experimented on mice to avoid saccharin(糖精)by feeding them at the same time with the sweetener and a drug that while harming their immune systems caused stomach upsets. Connecting the saccharin with stomach pains, the mice quickly learned to avoid the sweetener. In order to get rid of this dislike for the sweetener, Ader fed the animals with saccharin again, this time without the drug, and was astonished to find that those mice that had received the highest amount of sweetener the first time died. He believed that saccharin alone weakened their immune systems enough to kill them.

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