Many nonverbal behaviours - smiling, blushing, shrugging - reveal our emotions. Once nonverbal behaviour, gesturing, exposes our thoughts. This book explores how we move our hands when we talk, and what it means when we do so. Susan Goldin-Meadow begins with an intriguing discovery: when explaining their answer to a task, children sometimes communicate different ideas with their hand gestures than with their spoken words. Moreover, children whose gestures do not match their speech are particularly likely to benefit from instruction in that task. Not only do gestures provide insight into the unspoken thoughts of children (one of Goldin-Meadow's central claims), but gestures reveal a child's readiness to learn and even suggest which teaching strategies might be most beneficial. In addition, Goldin-Meadow characterizes gesture when it fulfills the entire function of language (as in the case of Sign Languages of the Deaf), when it is reshaped to suit different cultures (American and Chinese), and even when it occurs in children who are blind from birth. Focusing on what we can discover about speakers - adults and children alike - by watching their hands, this book discloses the active role that gesture plays in conversation and, more fundamentally, in thinking. In general, we are unaware of gesture, which occurs as an undercurrent alongside an acknowledged verbal exchange. In this book, Susan Goldin-Meadow makes clear why we must not ignore the background conversation.