Reading library books to my one-year-old son this morning, I come across a book called Baby Talk by Margaret Miller. A handsome baby smiles on the cover. Turning the first page, we read the word "Hi" typed next to a cordial looking lad. The next page, however, features the word "No!" and a stubborn-looking baby with puckered lips, looking as if he's about to administer the kiss of death. On the next page a baby plays with his lip and says, "Mine!" The remaining pages present typical baby words. "Yes," makes no appearance; instead we read the ambivalent "Okay." "Please" and "Thank you" must be too advanced for the intended audience.
A baby's first words well set the stage for how he sees the world. I find Miller's emphasizing disobedience, bad manners, and possessiveness far more alarming than any ill effects of an adolescent reading Harry Potter.