What sorts of novels is Charlie reading? Why does Dr. Strauss steer Charlie away from books on psychology?

Charlie is reading history and geography books. He is also reading novels like Robinson Crusoe. In my opinion, he is told to stay away from psychology book because he wo't be able to understand them properly. According to the text, it seems as if Dr. Strauss wants to make sure he is ready.

Besides history, geography, and arithmetic, Miss Kinnian said I should start to learn a few foreign languages. Dr. Strauss gave me some more tapes to play while I sleep. I still don't understand how that conscious and unconscious mind works, but Dr. Strauss says not to worry yet. He asked me to promise that when I start learning college subjects next week I wouldn't read any books on psychology-that is, until he gives me permission.