One of the reasons Americans tend to be more outgoing is because of school structure. In Chinese and Japanese schools, students are in the same homeroom for many years and the teacher shifts grades to stay with the same students. In American schools, students have different classmates and teachers every year, so the raw number of people they encounter at school and maintain ties with is magnitudes higher. The social complexity that the average American has to manage from a young age is a level that a Chinese or Japanese may never have to handle in their entire lives.(Zhu Su)