Why are boys in Hainan stingy?

According to my usual observation, there are not only boys but also girls. At present, only one child is allowed in China. In Hainan, the place is not big. Children can only follow their parents or a few familiar people. They are young and everyone is used to him. They have little contact with outsiders and have no sense of getting along. They just think that the earth revolves only for him. So some Hainan children will be a little stingy.