What makes one person more intelligent than another? What makes one person a genius, like the brilliant Albert Einstein, and another person a fool? Are people born intelligent or stupid, or is intelligence the result of where and how you live? These are very old question and the answers to them are still not clear. We know, however, that just being born with a good mind is not enough. In some ways, the mind is like a leg or an arm muscle. It needs exercise. Mental (done with the mind) exercise is particularly important for young children. (78) Many child psychologists (心理学家) think that parents should play with their children more often and give them problems to think about. (79)The children are then more likely to grow up bright and intelligent. If, on the other hand, children are left alone a great deal with nothing to do, they are more likely to become dull and unintelligent. Parents should also be careful what they say to young children. According to some psychologists, if parents are always telling a child that he or she is a fool or an idiot, then the child is more likely to keep doing silly and foolish things. So it is probably better for parents to say very positive (helpful) things to their children, such as 'That was a very clever thing you did.' or' You are such a smart child.' The words 'intelligent' and 'brilliant' in the first paragraph probably mean ______ while 'dull' in the second paragraph means ______.