This video demonstrates how looking at someone's mouth movements affects the way we hear what they are saying. The man in the video is saying "bah, bah, bah," but when the same audio recording is played while he mouths out "fah, fah, fah," it sounds like he is saying "fah, fah, fah."
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects