Airs Thursday, November 24, at 7 p.m. Two words: Thank you. They sound simple enough. But there is always more to a topic, phrase, or ritual than one might think. Margaret Visser, the author of Much Depends on Dinner, is best known for her books about the history, anthropology, and mythology of everyday life. Now she has turned her scholarly eye towards gratitude. The result is a book called The Gift of Thanks: The Roots, Persistence and Paradoxical Meanings of a Social Ritual. It's published by Harper Collins.