Intuitive use is a notoriously vague concept. Several research groups have been developing a wealth of definitions and ways of measuring intuitive use that show only few commonalities. Here we review previous approaches combined with newer theoretical developments in psychology. From this review we propose that high effectiveness, low cognitive effort and a strong metacognitive feeling of fluency are the defining characteristics of intuitive use whereas many other measures are typical correlates of these defining characteristics. Distinguishing between defining characteristics and typical correlates allows researchers and practitioners to refer to a common measurement definition of intuitive use while maintaining their flexibility to adapt measures according to their needs.

Online privacy policies should enable users to make informed decisions. Current text policies, however, lack usability: users often miss crucial information and consent to them without reading. Visual representation formats may increase comprehension, but are rarely used in practice. In an iterative design process we gathered qualitative feedback on typical policy contents and on existing and newly designed representation formats. We developed design guidelines and a Visual Interactive Privacy Policy based on the Privacy Policy Nutrition Label enriched with control options and further interactive elements. In an empirical evaluation, both visual representations received higher ratings of attractiveness, stimulation, novelty and transparency compared to a standard policy long text. Interactivity improved time spent with the policy. There were no effects on conversion rate, perceived control or perceived trust, efficiency and perspicuity. More research is needed, especially with regard to the cost-benefit ratio of visual privacy policies.

Cognitive aids - artefacts that support a user in the completion of a task at the time - have raised great interest to support healthcare staff during medical emergencies. However, the mechanisms of how cognitive aids support or affect staff remain understudied. We describe the iterative development of a tablet-based cognitive aid application to support in-hospital resuscitation team leaders. We report a summative evaluation of two different versions of the application. Finally, we outline the limitations of current explanations of how cognitive aids work and suggest an approach based on embodied cognition. We discuss how cognitive aids alter the task of the team leader (distributed cognition), the importance of the present team situation (socially situated), and the result of the interaction between mind and environment (sensorimotor coupling). Understanding and considering the implications of introducing cognitive aids may help to increase acceptance and effectiveness of cognitive aids and eventually improve patient safety.

Pursuing the goal of a healthy diet may be challenging, especially when self-control resources are low. Yet many persuasive user interfaces fostering healthy choices are designed for situations with ample self-control, e.g. showing nutritional information to support reflective decision making. In this paper we propose that under low self-control, persuasive user interfaces need to rely on simple heuristic decision making to be successful. We report an experiment that tested this assumption in a 2 (low vs. high self-control) x 2 (calorie vs. heuristic information) design. The results reveal a significant interaction effect. Participants with low self-control resources chose the healthy snack more often when snacks were labelled with heuristic information than when they were labelled with calorie information. Both strategies were about equally successful for participants with high self-control. Exploiting situations of low self-control with heuristic information is a new and promising approach to designing persuasive technology for healthy eating.

Virtual Reality can impose cognitive demands on users and influence their task performance. These cognitive demands, however, have been difficult to measure precisely without inducing breaks of presence. Based on findings in psychological science on how motion trajectories reflect underlying cognitive processes, we investigated entropy (i.e. the degree of movement irregularity) as an unobtrusive measure of mental workload. Entropy values were obtained from a time-series history of controller movement data. Mental workload is considered high over a given time interval, when the measured entropy is high as well. By manipulating the difficulty of a simple rhythm game we could show that the results are comparable to the results of the NASA-TLX questionnaire, which is currently used as the gold standard in VR for measuring mental workload. Thus, our results pave the way for further investigating the entropy of controller movements as a precise measurement of mental workload in VR.

There is a widely-held belief in the TEI and games communities that using tangible props enhances the player performance and gaming experience. Building on prior research in gaming, we studied people playing a video game using a gestural interface without props, with an incomplete or a complete tangible prop. The interaction with the tangibles was judged to be more natural, led to higher flow experience and was preferred, but there were no differences regarding performance, enjoyment, autonomy, presence and mental effort. There was a tendency that especially the incomplete tangible prop was judged as less intuitive and people felt less competent in gameplay. In contrast to prior research, the results show that tangible interaction is not always more beneficial than gestural interaction and that, especially for incomplete tangibles, any beneficial effects may be domain-dependent.

Conceptual Metaphor Theory is able to predict how physical object properties can trigger associated abstract content. Based on prior research on texture metaphors, we hypothesised that even incidental sensations of texture can influence the subjective evaluation of user experience and the interpretation of an ambiguous social situation. In three studies users interacted with smooth and rough versions of cases of mobile devices (Study 1), trackpads (Study 2) and tangibles for interactive gameplay (Study 3). Despite convincing evidence collected in earlier studies, the results confirmed none of the hypotheses in any of the three studies. Possible reasons and their relevance for the use of metaphors in HCI and tangible interfaces are discussed and conclusions for further applications of rough/smooth metaphors are drawn.