David McNeill, a pioneer in the ongoing study of the relationship between gesture and language, here argues that gestures are active participants in both speaking and thinking. He posits that gestures are key ingredients in an “imagery-language dialectic” that fuels speech and thought. The smallest unit of this dialectic is the growth point, a snapshot of an utterance at its beginning psychological stage. In the central growth point comes from a Tweety Bird cartoon. Over the course of twenty-five years, the McNeill Lab showed this cartoon to numerous subjects who spoke a variety of languages, and a fascinating pattern emerged. The shape and timing of gestures depends not only on what speakers see but on what they take to be distinctive; this, in turn, depends on the context.  Those who remembered the same context saw the same distinctions and used similar gestures; those who forgot the context understood something different and changed gestures or used none at all. Thus, the gesture becomes part of the growth point—the building block of language and thought. is an ambitious project in the ongoing study of how we communicate and how language is connected to thought.