The period of adolescence, i.e., the period between childhood and adulthood, may be long or short, depending on social expectations and on society's definition as to what constitutes maturity and adulthood. In primitive societies adolescence is frequently a relatively short period of time, while in industrial societies with patterns of prolonged education coupled with laws against child labor, the period of adolescence is much longer and may include most of the second decade of one's life. Furthermore, the length of the adolescent period and the definition of adulthood status may change in a given society as social and economic conditions change. Examples of this type of change are the disappearance of the frontier in the latter part of the nineteenth century in the United States, and more universally, the industrialization of an agricultural society. In modern society, ceremonies for adolescence have lost their formal recognition and symbolic significance and there no longer is agreement as to what constitutes initiation ceremonies. Social ones have been replaced by a sequence of steps that lead to increased recognition and social status. For example, grade school graduation, high school graduation and college graduation constitute such a sequence, and while each step implies certain behavioral changes and social recognition, the significance of each depends on the socio-economic status and the educational ambition of the individual. Ceremonies for adolescence have also been replaced by legal definitions of status roles, rights, privileges and responsibilities. It is during the nine years from the twelfth birthday to the twenty-first that the protective and restrictive aspects of childhood and minor status are removed and adult privileges and responsibilities axe granted. The twelve-year-old is no longer considered a child and has to pay full fare for train, airplane, theater and movie tickets. Basically, the individual at this age loses childhood privileges without gaining significant adult rights. At the age of sixteen the adolescent is granted certain adult rights which increases his social status by providing him with more freedom and choices. He now can obtain a driver's license: he can leave public schools and he can work without the restrictions of child labor laws. At the age of eighteen the law provides adult responsibilities as well as rights: the young man can now be a soldier, but he also can marry without parental permission. At the age of twenty-one the individual obtains his full legal rights as an adult. He now can vote, he can buy liquor, he can enter into financial contracts, and he is entitled to run for public office. No additional basic rights are acquired as a function of age after majority status has been attained. None of these legal provisions determine at what point adulthood has been reached but they do point to the prolonged period of adolescence. The period of adolescence is much longer in industrial societies because ______.