In the past decade, the field of Tangible Interaction (TI) has gained significant interest. As a result, numerous systems, theories and frameworks have been developed with this vision in mind. This has led to various instantiations of TI that seem developed to make digital information tangible, rather than to optimally use and combine all important qualities of TI. We believe that TI has more to offer than what has been used advantageously so far. Therefore, this paper reflects on the foundations of TI and identifies three qualities of control and representation in TI based on existing systems, theories and frameworks.

This article presents an experimental study of privacy-related attitudes and behaviors regarding a music recommender service based on two types of user modeling: personality traits and musical preferences. Contrary to prior expectations and attitudes reported by participants, personality traits are frequently disclosed to the system and other users, indicating that embedded modeling of user personality does not represent an acceptance barrier. Discrepancies between privacy attitudes and behaviors have been reported before in the context of e-commerce applications, but the corresponding studies could not exclude several conflicting hypotheses, such as participants expressing attitudes outside the context of specific privacy dilemmas and contact with researchers, which may have mitigated perceived privacy risks. Arguably, these are fundamental problems in empirical investigations into privacy that apply to most published works relating to privacy and user modeling. Measures to control these factors in this study are discussed, and methodological suggestions for future research are presented.Keywords: privacy; personalization; music recommender; user profile daptive systems and personalized systems in particular rely on having appropriate and sufficient information about their users to operate optimally. This could, for example, include information about the identity of the user, earlier usage of a service, the user's preferences and dislikes, and many other types of data (Kobsa, 2001). The collection and processing of such information can conflict with privacy concerns (Kobsa, 2002). More specifically, it has been suggested that privacy-related concerns are contingent on the kind of information collected (Ackerman, Cranor, & Reagle, 1999;Adams & Sasse, 2001;Bellotti & Sellen, 1993), the degree of control users have over disclosure (Bellotti & Sellen, 1993;Olivero & Lunt, 2004), the degree of accessibility (Adams & Sasse, 2001;Bellotti & Sellen, 1993), or the way the information is used (Adams & Sasse, 2001;Bellotti & Sellen, 1993). Information may be collected by the user's explicit and intentional input, or information may be collected implicitly by monitoring the users as they go about their own tasks or activities. Implicit collection of information is an essential element of scenarios relating to Ambient Intelligence (Aarts, Harwig, & Schuurmans, 2001) and can lead to privacy issues because of a lack of awareness and control by the people concerned (Cranor, 2004;Kobsa & Schreck, 2003;Nguyen & Mynatt, 2002).In the context of this study, the term privacy refers to a boundary control process in which individuals regulate when, how, and to what extent information about them is communicated to others. This interpretation is based on the definitions by Westin (1967) and Altman (1975). In this study, the emphasis is on information privacy rather than interpersonal or social privacy. Information privacy refers to the claim by individuals that data about themselves should generally not be made available to other indivi...

We present an empirical study regarding the relative importance of complying with privacy related guidelines in the context of a Health Monitoring System. Participants were confronted with text scenarios describing privacy related aspects of a health monitoring service for daily use at home. Participants assessed the relative importance to them of simplified variants of the OECD (Organization of Economic Cooperation and Development) guidelines for the protection of personal data. The guidelines that relate to Insight and Openness were most valued. The guidelines relating to Modification and Data Quality were valued least by most participants in this context. Methodological challenges were encountered on the way, which reveal the complexity of conducting empirical investigations of privacy aspects of human-computer interaction.

This article focuses on the conceptual relation between the user's input and a system's output in interaction with smart tangible objects. Understanding this input-output relation (IO relation) is a prerequisite for the design of meaningful interaction. A meaningful IO relation allows the user to know what to do with a system to achieve a certain goal and to evaluate the outcome. The work discussed in this article followed a design research process in which four concepts were developed and prototyped. An evaluation was performed using these prototypes to investigate the effect of highly different IO relations on the user's understanding of the interaction. The evaluation revealed two types of IO relations differing in functionality and the number of mappings between the user and system actions. These two types of relations are described by two IO models that provide an overview of these mappings. Furthermore, they illustrate the role of the user and the influence of the system in the process of understanding the interaction. The analysis of the two types of IO models illustrates the value of understanding IO relations for the design of smart tangible objects.

Abstract. Privacy is a major concern for the design and user acceptance of pervasive technology. Investigating privacy poses several methodological challenges. A popular approach involves surveying reactions of people to scenarios that highlight privacy issues. This paper examines the validity of this approach. It reports an experiment that compared people's ability to correctly judge compliance to privacy principles when scenarios are presented in video versus textual form. It was found that such privacy-related concepts are hard to understand, leading to a large number of erroneous judgments regardless of medium and that interpretation varied across media. Comprehension in such studies can be improved, if a text scenario is preceded by a video-based version.