资料题：According to the passage, twins（　）。

Each child has his individual pattern of social, as well as physical, development.Some of it depends on his home life and his relationships with the people who love him.Children in large families learn how t get along with others through normal brother-sister play and tussles.An only child, on the other hand, may have to learn his lessons in social living through hard experiences on the playground or in the classroom.Twins who always have one another to lean on may be slow in responding to others because they do not need anyone else.A child who is constantly scolded and made to feel he does everything wrong may have a difficult time developing socially.He may be so afraid of displeasing the adults around him that he keeps to himself ( where he can't get into trouble), or he may take the opposite route and go out of his way to create trouble.Like the isolated child, he too may return to infantile pleasures, developing habits that will satisfy him, but create barriers toward social contact.