Dr. Peter Marshall, a child psychologist and author of “Now I Know Why Tigers Eat Their Young” says: “Privacy’s important for teens partly because they need to separate. It’s tempting to think that they’re just goofing off, but they spend a large part of their time just thinking about things, trying to figure out who they are, who they want to become. There’s a lot of work for them to do, and they need some space to do it.”