Speech Planning and Dynamics

What do we do when we are about to utter speech? On which linguistic units do we rely? How do these units evolve from childhood to adulthood, or across time for a given language? How do we assemble these units under the influences of syntactic, phonological and prosodic rules? Do we plan the whole sequence at once? Do we plan the movements of the tongue, jaw, and lips underlying speech in the same way that we plan other movements? What tools have scientists developed to investigate these questio