How do user-defined gestures for mixed reality change when users’ hands are engaged in tasks? To address this question, we conducted a gesture elicitation study to understand user preferences and the characteristics of gestures conceptualized in three scenarios with varying levels of hand constraints, namely: "both hands free", "one hand fixed", and "both hands busy". We analyzed these gestures across multiple dimensions and compared our findings with those from prior research. Our results indicate that when both hands are occupied, users tend to favor head gestures over those involving other body parts, such as the eyes or legs. Additionally, we found that most of the proposed gestures were metaphorical, with many influenced by legacy bias. These insights enhance our understanding of how hand constraints influence gesture choices in mixed reality scenarios.

Mobile health applications for weight maintenance offer self-monitoring as a tool to empower users to achieve health goals (e.g., losing weight); yet maintaining consistent self-monitoring over time proves challenging for users. These apps use push notifications to help increase users’ app engagement and reduce long-term attrition, but they are often ignored by users due to appearing at inopportune moments. Therefore, we analyzed whether delivering push notifications based on time alone or also considering user context (e.g., current activity) affected users’ engagement in a weight maintenance app, in a 4-week in-the-wild study with 30 participants. We found no difference in participants’ overall (across the day) self-monitoring frequency between the two conditions, but in the context-based condition, participants responded faster and more frequently to notifications, and logged their data more timely (as eating/exercising occurs). Our work informs the design of notifications in weight maintenance apps to improve their efficacy in promoting self-monitoring.

Physical multi-touch spherical displays can provide a direct, hands-on, embodied interaction experience with global visualization data like ocean temperatures and currents. However, current commercially available displays may be cost-prohibitive for educational institutions and/or non-profits to acquire. Virtual globe-based visualizations like Google Earth are a potential alternative, but it is not clear how well the interactive affordances of physical spheres may transfer to the virtual. We conducted a within-subjects comparative study with 21 participants who completed similar tasks on a physical and a virtual spherical interface platform, which were designed to be as similar as possible, in order to allow us to compare the interaction experiences. Our results overall showed no significant difference be-tween usability or task time on the two platforms. In their qualitative feedback, participants noticed the differences between the physical sphere and virtual sphere in terms of effort and motor demand. Our research implies that, in resource-constrained environments, a virtual globe can be a sufficient substitute for a physical sphere from a usability perspective.

With the prevalence of risks encountered by youth online, strength-based approaches such as nudges have been recommended as potential solutions to guide teens toward safer decisions. However, most nudging interventions to date have not been designed to cater to teens' unique needs and online safety concerns. To address this gap, this study provided a comprehensive view of adolescents' feedback on online safety nudges to inform the design of more effective online safety interventions. We conducted 12 semi-structured interviews and 3 focus group sessions with 21 teens (13 - 17 years old) via Zoom to get their feedback on three types of nudge designs from two opposing perspectives (i.e., risk victim and perpetrator) and for two different online risks (i.e., Information Breaches and Cyberbullying). Based on the teens' responses, they expressed a desire that nudges need to move beyond solely warning the user to providing a clear and effective action to take in response to the risk. They also identified key differences that affect the perception of nudges in effectively addressing an online risk, they include age, risk medium, risk awareness, and perceived risk severity. Finally, the teens identified several challenges with nudges such as them being easy to ignore, disruptive, untimely, and possibly escalating the risk. To address these, teens recommended clearer and contextualized warnings, risk prevention, and nudge personalization as solutions to ensure effective nudging. Overall, we recommend online safety nudges be designed for victim guidance while providing autonomy to control their experiences, and to ensure accountability and prevention of risk perpetrators to restrict them from causing harm.