Generation gap refers to the difference in ideas, feelings, and interests between the older and younger people. It is especially considered as causing a lack of communication and understanding between the two generations. There is apparent generation gap between the young and the old nowadays. The younger generation is essentially different from the older generation. The young people live in a new age completely different from the old. They have grown up more happily and are not so dependent on adults as their parents were. They are better educated and enjoy more freedom. They easily accept new things and new ideas. They are more concerned with the present and the future, whereas the world of the older people has vanished, and they do not understand all of the problems of the modern world. They grew up in a world which was different from today's world. They often talk about 'the good old days' and tend to assert old things and ideas. They don't like to feel that their beliefs and values are being questioned and threatened. They would like the young to learn from them, but the young refuse to accept their values. They cannot understand why the young complain about the conventional things and old systems and why they want to make changes in these things to fit the needs of modern society, As a result, the old people think the young are not what they were, and most young people are unable to learn from the parents and elders who they will never be. In order to reconcile the differences, both generation should realize that the world has changed, and that new responses are necessary for many of the problems of society. Besides, some forms of organizations should be established to help the young and the old exchange their ideas and strengthen their mutual understanding so as to bridge the gap. One important reason for the difference existing between the young and the old is that ______.