How do we do what we do? How do we play tennis, have conversations, or go shopping? At a finer grain, how do we recognize familiar objects such as bouncing balls, words, smiles, faces, jokes? Carry out actions such as returning a serve, pronouncing a word, selecting a book off the shelf? Cognitive scientists are interested in explaining how these kinds of extraordinarily sophisticated behaviors come about. They aim to describe cognition: the underlying mechanisms, states and processes. For decades, cognitive science has been dominated by one broad approach. That approach takes cognition to be the operation of a special mental computer, located in the brain. Sensory organs deliver up to the mental computer representations of the state of its environment. The system computes a specification of an appropriate action. The body carries this action out.