When we realize we've said something in error and we pause to go back to correct it, we stop gesturing a couple of hundred milliseconds before we stop speaking. Such sequences suggest the startling notion that our hands "know" what we're going to say before our conscious minds do, and in fact this is often the case. Gesture can mentally prime a word so that the right term comes to our lips. When people are prevented from gesturing, they talk less fluently; their speech becomes halting because their hands are no longer able to supply them with the next word, and the next. Not being able to gesture has other deleterious effects: without gesture to help our mental processes along, we remember less useful information, we solve problems less well, and we are less able to explain our thinking. Far from tagging along as speech's clumsy companion, gesture represents the leading edge of our thought.