Embodied conversational agents (ECA) and speech-based human-machine interfaces can together represent more advanced and more natural human-machine interaction. Fusion of both topics is a challenging agenda in research and production spheres. The important goal of human-machine interfaces is to provide content or functionality in the form of a dialog resembling face-to-face conversations. All natural interfaces strive to exploit and use different communication strategies that provide additional meaning to the content, whether they are human-machine interfaces for controlling an application or different ECA-based human-machine interfaces directly simulating face-to-face conversation.

Coverbal Synchrony in Human-Machine Interaction presents state-of-the-art concepts of advanced environment-independent multimodal human-machine interfaces that can be used in different contexts, ranging from simple multimodal web-browsers (for example, multimodal content reader) to more complex multimodal human-machine interfaces for ambient intelligent environments (such as supportive environments for elderly and agent-guided household environments). They can also be used in different computing environments-from pervasive computing to desktop environments. Within these concepts, the contributors discuss several communication strategies, used to provide different aspects of human-machine interaction.