You hear the same complaint all the time: “My memory is terrible.” Is it all in the mind, or do real changes take place in the brain with the passing of time? The answer is that the brain’s cells, the neurons, decline and die with age.However, according to Professor Arthur Shimamura of the University of California, people vary greatly in how they change mentally with age, as well as how much their mental ability declines. There are three main ways in which mental function changes.The first concerns speed, such as how quickly you can react to fast-moving incidents on the road.Drivers in their late teen react quickly but often drive too fast, while the over-60’s are more careful but react more slowly.72 This type of mental slowing results from a reduction in the efficiency with which the brain’s neurons work. 73 The fact that adults find it harder to learn musical instrument than children points to a second type of mental decline, the loss of learning ability with agE.The part of the brain which is known to control new learning is particularly sensitive to the effects of aging.The means we have to depend more on diaries and other mental aids as we get older, take longer to learn a new language and are slower to master new things at work. “Working memory” is the third brain function that is sensitive to the effects of aging.Absent-mindedness occurs at all ages because of imperfections in the working memory system. For example, you may continually lose your glasses, or find yourself walking into a room of your house only to find that you cannot remember what you came for.Such absent-mindedness also occurs more often as we get older. 74 However, evidence also shows that the principle “use it or lose it” applies to the aging brain.Professor Shimamura studied a group of university professors who were still mentally active, and compared their performance on neuropsychological tests with that of others of their age group, as well as with younger people.He found that on several tests of memory, the mentally active professors in their 60’s and early 70’s performed better than those of the same age, and as well as the younger group. 72.Memory gets worse as people grow older because _________. A.the brain starts to produce too many neuronsB.cells in the brain stop the neurons from working C.the brain’s neurons don’t work as well as beforeD.when people get old, they complain too much 73.Which of the following well-known sayings best expresses the idea of the third paragraph? A.A bird in the hand is worth two in the bushB.You can’t teach an old dog new tricks.老狗学不会新把戏。意思就是新人的学习能力更强，更快接受新事物。 C.Where there’s a will, there’s a way.D.It’s never too old to learn. 74.We can conclude from Shimamura’s test on the professors that _________. A.active minds might keep their memory betterB.memory can improve with the time passing on C.all of the old people will suffer memory lossD.the principle “use it or lose it” is obviously wrong 75.This passage is mainly about _________. A.youth and agingB.problems of getting old C.secrets of a good memoryD.aging and mental ability