People have a deeply rooted need to experience control and be effective in interactions with their environments. At present times, we are surrounded by intelligent systems that take decisions and perform actions for us. This should make life easier, but there is a risk that users experience less control and reject the system. The central question in this thesis is whether we can design intelligent systems that have a degree of autonomy, while users maintain a sense of control. We try to achieve this by giving the intelligent system an 'expressive interface’: the part that provides information to the user about the internal state, intentions and actions of the system. We examine this question both in the home and the work environment.We find the notion of a ‘system personality’ useful as a guiding principle for designing interactions with intelligent systems, for domestic robots as well as in building automation. Although the desired system personality varies per application, in both domains a recognizable system personality can be designed through expressive interfaces using motion, light, sound, and social cues. The various studies show that the level of automation and the expressive interface can influence the perceived system personality, the perceived level of control, and user’s satisfaction with the system. This thesis shows the potential of the expressive interface as an instrument to help users understand what is going on inside the system and to experience control, which might be essential for the successful adoption of the intelligent systems of the future.<br/
