HCI perspectives on behavior change support systems

In this thesis we have focused on the techniques and principles from the field of human computer interaction to design, implement and evaluate the Kristina coaching system. We paid special attention to the effects on user perception when feedback was presented in different formats. Kristina is a multi-­‐device coaching system. It uses data from different input devices to measure physical activity and medication intake. Overviews and feedback messages can be received on different output. Principles from the field of human computer interaction can contribute to the design and the evaluation of early stage health behavior change support systems. Without evaluation studies in the traditional clinical sense we were able to investigate the user perception of the system and whether the system was supporting the users as it was supposed to do. We have presented the results of a context mapping study and two online questionnaires. These results were input for a requirement analysis for the first prototype of the Kristina system. We have presented five user evaluation studies to investigate differences in user perception between feedback messages presented in plain text or by a virtual human. Results from the different user evaluation studies showed that feedback messages presented by a virtual human did not improve the user perception of the coaching application when short and frequent messages were received on a smartphone. Feedback messages presented by a virtual human did improve the user perception of the coaching application when weekly feedback messages were sent to a personal computer or laptop. Results from the log data of the six week user evaluation study showed trends in the effects on performance and adherence. We found differences between the control group and the text group on the number of uploads of physical activity data and the level of physical activity. Participants from the text group showed a higher number of physical activity data uploads compared to participants from the control group. The level of physical activity of the participants of the text group was higher compared to the control group. Glanceablilty, enabling users to understand information with low cognitive effort, is important when feedback messages are received on a smartphone. The use of a virtual human does not satisfy the requirements of glanceability