Of all the components of a good night"s sleep, dreams seem to be least within our control. In dreams, a window opens into a world where logic is suspended and dead people speak. A century ago, Freud stated that dreams were the disguised shadows of our unconscious desires and fears; by the late 1970s,neurologists(神经学家) had switched to thinking of them as just "mental noise". Now researchers suspect that dreams are part of the mind"s emotional thermostat, regulating moods while the brain stops thinking logically. And one leading authority says that these intensely powerful mental events can be not only harnessed but actually brought under conscious control, to help us sleep and feel better. "It"s your dream," says Rosalind Cartwright, chair of psychology at Chicago"s Medical Center. "If you don"t like it, change it."The link between dreams and emotions shows up among the patients in Cartwright"s clinic. Most people seem to have more bad dreams early in the night, progressing toward happier ones before awakening, suggesting that they are working through negative feelings generated during the day. (In studying divorced couples, Cartwright has found that those who don"t follow this dream progression have a much harder time getting over the hurt.) Because our conscious mind is occupied with daily life we don"t always think about the emotional significance of the day"s events—until, "it appears, we begin to dream.And this process need not be left to the unconscious. Cartwright believes one can exercise conscious control over repeated bad dreams. As soon as you awaken, identify what is upsetting about the dream. Imagine how you would like it to end instead; the next time it occurs, try to wake up just enough to control its course. With much practice people can learn to, literally, do it in their sleep.At the end of the day, there"s probably little reason to pay attention to our dreams at all unless they keep us from sleeping or we wake up in a panic. Terrorism, economic uncertainties and general feelings of insecurity have increased people"s anxiety. Those suffering from persistent nightmares should seek help from a therapist. For the rest of us, sleep—or rather dream—on it and you"ll feel better in the morning. Cartwright believed with much practice, we can learn to

A. control what dreams to dream
B. sleep well without any dreams
C. wake up in time to stop the bad dreams
D. identify what is upsetting about the dreams