听力原文： Many people suffer from some form. of extreme anxiety. Some experience occasional attacks of panic for no apparent reason. Others go around in state of continual uneasiness. The usual way of controlling anxiety is with drugs, which cure none of the conditions described but do help patients manage their anxiety. Patients who take these drugs say that they are able to work, to sleep, and to go places they had feared to visit. But the effects of the drugs on the human body, especially on the nerve system, have been unknown. We have started a series of studies to identify the effects of the drugs on the brain and have gained some insight into the cost and benefits of the anti-anxiety drugs. They are valuable because they can reduce the effects of anticipated failure, frustration and disappointment. But their value demands a price. Two effects of the drugs are obviously harmful. They reduce a person's ability to react to changes in the environment; and more important, they keep a person from developing persistence in the face of unexpected troubles. Since it is fairly sure that people will meet problems they have not expected, this effect may make the price of anti-anxiety drugs too high. (30)