Presently, there are user interfaces that allow multimodal interactions. Many existing research and prototype systems introduced embodied agents, assuming that they allow a more natural conversation or dialogue between user and computer. Here we will first take a look at how in general people react to computers. We will look at some of the theories, in particular the CASA (“Computers Are Social Actors”) paradigm, and then discuss how new technology, for example ambient intelligence technology, needs to anticipate the need of humans to build up social relationships. One way to anticipate is to do research in the area of social psychology, to translate findings there to the humancomputer situation and to investigate technological possibilities to include human-human communication characteristics in the interface. For that reason we will discuss embodied conversational agents, the role they can play in human-computer interaction (in face-to-face conversation), in ambient intelligence...