I Can Read Your Mind!!!

What follows is a well-traveled card trick / mindreading illusion that keeps popping up online, most recently in the form of a PowerPoint presentation purporting to be (though it almost certainly is not) the work of master stage magician David Copperfield.

The illusion can be startling — until you figure out how it works, that is, at which point you may find yourself wondering how anyone could possibly fall for such a simple, obvious deception.