Longitudinal studies have traditionally been seen as too cumbersome and labor-intensive to be of much use in research on Human-Computer Interaction (HCI). However, recent trends in market, legislation, and the research questions we address, have highlighted the importance of studying prolonged use, while technology itself has made longitudinal research more accessible to researchers across different application domains. Aimed as an educational resource for graduate students and researchers in HCI, this book brings together a collection of chapters, addressing theoretical and methodological considerations, and presenting case studies of longitudinal HCI research. Among others, the authors: - discuss the theoretical underpinnings of longitudinal HCI research, such as when a longitudinal study is appropriate, what research questions can be addressed and what challenges are entailed in different longitudinal research designs reflect on methodological challenges in longitudinal data collection and analysis, such as how to maintain participant adherence and data reliability when employing the Experience Sampling Method in longitudinal settings, or how to cope with data collection fatigue and data safety in applications of autoethnography and autobiographical design, which may span from months to several years present a number of case studies covering different topics of longitudinal HCI research, from "slow technology", to selftracking, to midair haptic feedback, and crowdsourcing.

Evangelos Karapanos is Associate Professor at the Department of Communication & Internet Studies of the Cyprus University of Technology. He is a long advocate for more longitudinal studies in HCI research, starting with his early work on "User Experience over time", and more recently with his work on the "23 ways to nudge" framework, that found that only 36% of the studies of nudging in HCI had a duration longer than a day.Jens Gerken is Professor of Media Informatics and Human-Computer Interaction at the Westfälische Hochschule in Gelsenkirchen, Germany. His interest and expertise about longitudinal research dates back more than 10 years and includes work aiming for a common taxonomy on longitudinal research designs as well as the design of tools and methods to apply longitudinal research. Jesper Kjeldskov is Professor in Human-Computer Interaction and Head of Department of Computer Science at Aalborg University, Denmark. His work on research methods in Mobile HCI has been influential in the discussion of strengths and weaknesses of lab and field studies, and has advocated a mixed methods approach and extending the duration of studies from "snapshots of use" to longitudinal technology deployments in real world settings. Mikael B. Skov is Professor in Human-Computer Interaction and research leader in the Human-Centred Computing Group at the Department of Computer Science at Aalborg University, Denmark. His work on research methods in studying and evaluating technology in real life or in-situ has been influential within HCI research, and has focused on various application domains among others mobility and smart homes.