Human Spoken Interaction as a Complex Adaptive System explains how human spoken communication functions, combining two separate complex adaptive systems: the universal ‘interaction engine’ and language(s), which now number around 7,000. Siegel and Seedhouse offer a comprehensive overview of how the components and processes of the interaction engine work together to enable us to understand each other, whatever the language. Through combining Complexity Science and Conversation Analysis, this book explains how to simultaneously analyse spoken interaction on micro and macro scales. Detailed analyses of L2 learners reveal them to be simultaneously expert in using the interaction engine and inexpert in using the specific language. The study shows that the basic characteristics of the interaction engine are the same as for other life-related complex systems and that it is possible to access the perspectives of participants inside this complex adaptive system as it is evolving.