When commuting into Chicago on the train, I always followed the “unwritten codes of conduct”—such as, no conversations with people sitting next to you if you don’t know them. That was tough on a guy like me who has never met a stranger. I love talking to new people! Although I kept the code of silence, I realized that you can still learn something about people based on the section of the newspaper they read. So I’d watch to see what they turned to first: The business section? Sports? Politics? Current events? Their choices revealed their interests.

Our choices are always…