单选题
What Is Your Dog Thinking?
A. Your cute companion rests by your side, but is she dreaming of you? Does she feel guilty about stealing your steak off the kitchen counter and eating it for dinner? What is she trying to say with that annoying bark? Does she smile to you today? After decades of research, neuroscientists (神经系统学家)have begun to answer such questions, giving us access to the once-secret inner lives of our cute companions and even translating their barks and wags so mere humans can understand them. At the forefront of this effort is Stanley Coren, a behaviorist from the University of British Columbia, who draws on decades of research to explore the psychological motivations behind dogs' everyday behaviors.
B. Dogs have the same brain structures that produce emotions in humans. They have the same hormones (荷尔蒙)and undergo the same chemical changes that humans do during emotional states. Dogs even have what in humans is involved with love and affection.However, it is important not to go overboard: The mind of a dog is roughly equivalent to that of a human who is 2 to 2 1/2 years old. A child that age clearly has emotions, but not all possible emotions, since many emerge later in the path to adulthood.
C. Dogs go through their developmental stages much more quickly than humans do, attaining their full emotional range by the time they are 4 to 6 months old. A dog has the basic emotions: joy, fear, anger, disgust, excitement, contentment, distress, and even love. A dog does not have, and will not develop, more complex emotions, like guilt, pride, contempt, and shame, however. You might argue that your dog has shown evidence of feeling guilty. In the usual case, you come home and your dog starts avoiding you and showing discomfort and you then find his smelly brown deposit on your kitchen floor. It is natural to conclude that the dog's actions show a sense of guilt about its ill behavior.
However, this is simply the more basic emotion of fear. The dog has learned that when you appear and his droppings are visible on the floor, bad things happen to him. He will also never feel shame, so feel free to dress him in that ridiculous party costume.
D. Many people believe that dogs have dreams. Most dog owners have noticed that at various times during sleep, some dogs may quiver, suddenly move a leg, even utter angry sounds or snap at a sleep-created evil image, giving the impression that they are dreaming about something. At the structural level, the brains of dogs are similar to those of humans. In addition, during sleep the brain-wave patterns of dogs are similar to people's, and they exhibit the same stages of electrical activity that are observed in humans—all of which is consistent with the idea that dogs are dreaming.
E. Actually, it would be surprising if dogs didn't dream, since recent evidence suggests that animals simpler and less intelligent than dogs seem to do so. Neuroscientists Matthew Wilson and Kenway Louie of Massachusetts Institute of Technology have evidence that the brains of sleeping rats function in a way that definitely suggests dreaming. Much of the dreaming you do at night is associated with the activities you engaged in that day. The same seems to be the case in rats.
F. From studies of electrical recordings of the rats made while the rats were awake and learning a maze, Wilson and Louie found that some electrical patterns were quite specific and could be identified, depending on what the rat was doing. Later, when the rats were asleep and their brain waves indicated that they had entered the stage in which humans normally dream, these same electrical patterns appeared. The patterns were so clear and specific that the researchers were able to tell where in the maze the rat would be if it were awake, and whether it would be moving or standing still. Since a dog's brain is more complex than a rat's and shows the same electrical sequences, it is reasonable to assume that dogs dream as well.
G. There is also evidence that they dream about common dog activities. The human brain stem contains a special structure that keeps us from acting out our dreams. When scientists removed or inactivated this same part of the brain in dogs, they observed that the dogs began to move around, even though electrical recordings of the dogs' brains indicated that they were still fast asleep. The animals started to move only when the brain entered that stage of sleep associated with dreaming. During the course of a dream episode, the dogs actually began to execute the actions they were performing in their dreams. There is also an odd fact that small dogs have more dreams than big dogs do.
H. In the minds of most people, the equivalent of a dog's smiling is when he is wagging his tail. But there is actually one facial expression that comes close to what we mean by smiling in humans. In this expression, slightly opened jaws reveal the dog's tongue hanging over his front teeth. Frequently the eyes take on a teardrop shape at the same time, as if being pulled upward slightly at the outer comers. It is a casual expression that is usually seen when the dog is relaxed, playing, or interacting socially, especially with people.
I. Dogs are also capable of laughing, and they typically do so when they are playing. The laughter begins with the doggy equivalent of smiling but also includes a sound that is much like heavy breathing. Several years ago, animal behaviorist Patricia Simonet at Sierra Nevada College recorded those sounds while dogs played. In one experiment, Simonetnoticed that puppies ran around for joy when they heard recordings of these sounds; in another, she was able to show that these same sounds helped to calm dogs in an animal shelter.