You can’t see your sleeping pet’s brain waves, but its behavior can tell you when your cat might be dreaming. If you watch closely, you’ll see that as she falls asleep, her breathing becomes slow and regular with her body still. She has entered the first stage of sleep, called slow-wave sleep. After about 15 minutes you’ll notice a change in her breathing, Her eyes move under her closed lids, her paws twitch (抽动) and she flicks (轻拂) an ear. She has entered dreaming. Although she twitches and makes little grunting noises, messages from her brain to the large muscles in her legs are blocked, so she can’t run about. She is in a state of “sleep paralysis (麻痹)”.
Michel Jouvet, a French scientist, interrupted their sleep paralysis. Even though they were completely asleep, the dreaming cats began to run for balls that Jouvet couldn’t see and arched (成弓形) their backs at unseen enemies. He figured he was watching them act out their dreams! Obviously, the dreaming cats seemed to be practising important cat skills: following, catching, and fighting.
In another study, Matt Wilson recorded rats brain waves while they learned mazes (迷宫). One day, he left the brain-wave-recording machine on while the rats fell asleep. The pattern of brain waves in the sleeping rats matched the pattern from the maze so closely that Wilson could figure out exactly which part of the maze each rat was dreaming about!
Many researchers now think that in both people and animals, one purpose of dreams is to practise important skills and figure out recent learning. This may explain why so many people dream about fighting and escaping, skills that were probably important to our ancestors, and why dreaming affects our ability to learn.
Do all animals dream? From looking at the brain waves of sleeping animals, how often animals dream seems to be tied to body size. Cats dream about every 15 minutes, mice every 9 minutes, and elephants every 2 hours. And though cows and horses usually sleep standing up, they only dream when lying down.
12. What does Michel Jouvet find in his study?
A.The dreaming cats are practising their important skills. |
B.The dreaming cats are in a state of body paralysis. |
C.The eyes of dreaming cats move while bodies are still. |
D.The dreaming cats suddenly wake up and run for the ball. |
13. What can you learn from the passage?
A.Dreaming a lot can help humans learn more. |
B.Learning mazes is the basic skill for cats to learn. |
C.Fighting and escaping are not important skills for ancestors. |
D.Rats also dream to work out their recent learning. |
14. Which animal may dream most frequently?
A.Dogs. | B.Rats. |
C.Cows. | D.Elephants. |
15. How does the author develop this passage?
A.By making comparisons. | B.By using figures. |
C.By telling stories. | D.By showing facts. |