Here is a study I can kind of understand. Turns out according to some researchers at Southwest University, only children can grow up into more selfish adults. The gave some of the subjects MRI scans and those revealed that those who grew up as an only child were more creative and less agreeable than those with siblings because of the difference in the structure of their brain. The “onlies” had extra grey matter in their brains in the part which is associated with flexibility, imagination, and planning. Click here for more.