Psychologists Paul Ekman, Robert W. Levenson and Wallace Friesen enrolled professional actors in their experiment because they have been trained both to recall emotions from the past and not to be self conscious or embarrassed when asked to pose. After they were hooked up to equipment that electronically recorded the activity of their involuntary nervous systems, the actors were not told how to feel. But they were, instructed to move muscles in their faces to create smile, frowns, and expressions of anger, fear, sadness, happiness, disgust and surprise.
Two major findings came out of the study, published in Science magazine. One is that heart rate and skin temperature--both under the control of the autonomic nervous system--vary according to facial expression. This suggests some form. of communication between the brain's motor cortex(皮层), which governs voluntary movements, and areas in the brain's hypothalamus(下丘脑) that, instead, deal with unconscious bodily reactions to stimuli.
The other finding is that, contrary to what had been expected, the facial expressions that convey anger, fear, sadness and disgust each produce a different, but typical pattern of response from the involuntary nervous system. Though the psychologists have not yet detected correspondingly specific patterns for the other emotions they studied, they expect to identify them eventually.
As importantly, says Ekman, the new discoveries may, in time, have practical consequences because they "open the door to exploring how emotions cause physical disorders, and offer the possibility of using facial expressions therapeutically(治疗地)."
Scientists discovered that people's emotions are______.

A. controlled by their facial expression
B. influenced by their facial expression
C. identical with their facial expression
D. contrary to their facial expression