Sometimes, these individual pieces can break loose from their moorings and move to another place in an utterance. Second, there is a framework, or scaffolding, in which sounds can move around. Only sounds that belong to similar positions in this framework can exchange with each other. Finally, basic word forms are represented separately from their endings, or affixes, which are attached to them in this framework. Spoonerisms like these, and other slips of the tongue, can tell us about the planning steps that go on in our heads when we speak.
Tongue twisters are another source of data.
As we learn more about the way we plan our speech, we will be better equipped to find ways to help others who have trouble speaking because of a stroke, head wound, or developmental problem. It is difficult to develop methods to help others when we know s o little about the way the normal speech process works, and what can go wrong.