Sleeping is a big issue for most parents how to deal with it. There's not a lot of good scientific evidence on it. Anglo, Northern European, English society is really the only society that puts children in dark rooms by themselves to try to go to sleep. A couple hundred years ago, this isn't in my book, but I heard this since my book came out. The gin epidemic in London in the 1700s where people were going to bad drug and started rolling out of their children and crushing them.