Has the following ever happened to you? You are in a room full of people. Every one is talking and it is a big jumble. Then someone, somewhere in the room, says something of interest to you—like the name of the movie you saw last night, or the town you grew up in – or better yet, YOUR name– and all of a sudden, that person’s voice becomes more clear, more prominent. It is as though your ear is a camera with a zoom lens, and you have just zoomed in and focused.