What is the main idea of the lecture?

Questions 4 through 8. Listen to part of a lecture in an anthropology class.
Research on the play of young children has revealed that children have a culture of their own. Where do we find this culture? We find it in the sandbox and at the daycare center. We find it in the schoolyard. We find it wherever two or more children are together and reveal their private code of rules in their play.
Games and play are the realities of child culture. At the age of three, children are initiated into the secrets of child culture. Younger children eagerly pick up the rules of play from older children. Older children are the leaders of play activities because, of course, older children are experienced players. At age three, the ability to learn is enormous. There are so many skills to be mastered, including body language, spoken language, humor, songs, and so on. All of these are like keys that open the door to the fellowship of child culture. It’s a culture preserved in an oral tradition of songs and rhymes.
In preschool, children are extremely active. They have good control of their bodies, and they enjoy activity for its own sake. They love opportunities to run, climb, and jump. The play of preschool children has a broad range. Traditional games like hopscotch and ring around the rosy are an important part of their play. Just as important, however, are the open games, which are mostly created by the children themselves. These open games can be changed at will—kind of like improvisation on a theme.
In primary school, children are extreme in their physical activities and tend to express their emotions freely. Around the age of five, children start caring about the rules, and the games of five-year-olds tend to be more structured than the games of preschool children. Games are spontaneous and creative, but they also contain the rules, norms, and values of the group. At age six or seven, children like organized games in small groups, but they can be overly concerned with rules, or get carried away by team spirit. There are frequent quarrels, and many children indulge in punching, shoving, and wrestling.
4. What is the main idea of the lecture?
5. Listen again to part of the lecture. Then answer the question. "At the age of three, children are initiated into the secrets of child culture. Younger children eagerly pick up the rules of play from older children. Older children are the leaders of play activities because, of course, older children are experienced players."
What does the professor imply about child culture?
6. Why does the professor say this:
"There are so many skills to be mastered, including body language, spoken language, humor, songs, and so on. All of these are like keys that open the door to the fellowship of child culture."
7. What characterizes the play of preschool children?
8. How are the games of older children different from those of younger children?