If you do not use your arms or your legs for some time

If you do not use your arms or your legs for some time
If you do not use your arms or legs for a long time,they become weak.When you start using them again,they slowly become strong again.Everybody knows that.But many people do not know that memory works in the same way.
　　When someone says that he has a good memory,he really means that he keeps his memory in practice by using it.When someone else says that his memory is poor,he really means that he does not give it a chance to become strong.
　　If a friend says that his arms and legs are weak,we know that it is his own fault(过错).But if he tells us that he has a poor memory,many of us think that his parents are to blame (负责),and few of us know that it is just his own fault.
　　Have you ever noticed that some people who can’t read or write usually have better memories?This is because they can’t read or write and they have to remember things with their mind – they can’t write them down in a little notebook.They have to remember days,names,songs and stories,so they are always exercising their memories.
　　So if you want to have a good memory,learn from those people:practice remembering.
2.How will they become if you do not use your arms or legs for some time?
3.What should you do if you want to have a good memory?
4.Why can't some people read or write but they usually have better memories?