Someone old enough, but still insufficiently intellectually developed to know that the universe does not revolve around them. This person believes that everything is all about THEM, they fail to take responsibility for themselves, their errors, and the way other people respond to their sometimes painfully self-centered behavior and thinking.
Paul: Hey, Chelsea, give me that piece of pie.
Chelsea: But Dad, this is the last piece.
Paul: Go in and get yourself something else then.
Paul takes pie away from his daugher, she slumps back into the house.
Bek: (Aside to Kathryn) Paul is such a meanderthal - that poor kid loves banana cream pie!