Mainstream messaging platforms offer a variety of features designed to enhance user privacy, such as password-protected chats and end-to-end encryption (E2EE), which primarily protect message contents. Beyond contents, a lot can be inferred about people simply by tracing who sends and receives messages, when, and how often. This paper explores user perceptions of and attitudes toward 'untraceability', defined as preventing third parties from tracing who communicates with whom, to inform the design of privacy-enhancing technologies and untraceable communication protocols. Through a vignette-based qualitative study with 189 participants, we identify a diverse set of features that users perceive to be useful for untraceable messaging, ranging from using aliases instead of real names to VPNs. Through a reflexive thematic analysis, we uncover three overarching attitudes that influence the support or rejection of untraceability in messaging platforms and that can serve as a set of new privacy personas: privacy fundamentalists, who advocate for privacy as a universal right; safety fundamentalists, who support surveillance for the sake of accountability; and optimists, who advocate for privacy in principle but also endorse exceptions in idealistic ways, such as encryption backdoors. We highlight a critical gap between the threat models assumed by users and those addressed by untraceable communication protocols. In particular, many participants understood untraceability as a form of anonymity, but interpret it as senders and receivers hiding their identities from each other, rather than from external network observers. We discuss implications for the design of strategic communication and user interfaces of untraceable messaging protocols, and propose framing untraceability as a form of 'altruistic privacy', i.e., adopting privacy-enhancing technologies to protect others, as a promising strategy to foster broader adoption.

Premenstrual syndrome (PMS) is a prevalent disorder among women, often exacerbated by a lack of peer support due to associated stigmatization.Drawing inspiration from the established benefits of group therapy, particularly the sense of belonging it fosters, we developed a multi-chatbot group motivational interviewing system.The system consists of a facilitator bot and two peer bots, and simulates a group counseling environment for PMS management using Large Language Models (LLMs).We conducted a study with 63 participants and divided them into three conditions (no intervention, 1-on-1 chatbot, group chatbots) over two menstruation cycles for evaluation.Our findings revealed that participants in the group chat condition exhibited higher levels of engagement and language convergence with the chatbots.These participants were also able to engage in social learning and demonstrated motivation in coping through interactions with the chatbots.Finally, we discuss design implications for multi-chatbot interactions in supporting mental health.

Psychotherapy, such as cognitive-behavioral therapy (CBT), is effective in treating various mental disorders. Technology-facilitated mental health therapy improves client engagement through methods like digitization or gamification. However, these innovations largely cater to individual therapy, ignoring the potential of group therapy-a treatment for multiple clients concurrently, which enables individual clients to receive various perspectives in the treatment process and also addresses the scarcity of healthcare practitioners to reduce costs. Notwithstanding its cost-effectiveness and unique social dynamics that foster peer learning and community support, group therapy, such as group CBT, faces the issue of attrition. While existing medical work has developed guidelines for therapists, such as establishing leadership and empathy to facilitate group therapy, understanding about the interactions between each stakeholder is still missing. To bridge this gap, this study examined a group CBT program called the Serigaya Methamphetamine Relapse Prevention Program (SMARPP) as a case study to understand stakeholder coordination and communication, along with factors promoting and hindering continuous engagement in group therapy. In-depth interviews with eight facilitators and six former clients from SMARPP revealed the motivators and demotivators for facilitator-facilitator, client-client, and facilitator-client communications. Our investigation uncovers the presence of discernible conflicts between clients' intrapersonal motivation as well as interpersonal motivation in the context of group therapy through the lens of self-determination theory. We discuss insights and research opportunities for the HCI community to mediate such tension and enhance stakeholder communication in future technology-assisted group therapy settings.

Timbre exploration and creation are key tasks in electronic music composition. Modern synthesizers can produce thousands of unique timbres, but this complexity hinders musicians’ ability to explore these timbres effectively. We contribute SoundTraveller, an interactive timbre exploration system aimed at fostering electronic musicians’ creative processes. SoundTraveller allows the user to explore the timbral space using two modes: evolutionary and morphing, with which they can generate hundreds of unique timbres without the need to edit individual parameters. Our user study confirmed that SoundTraveller supported participants’ exploration, decreased their cognitive load, and increased their perceived creativity. Through analysis of our interview study, we contribute design considerations for timbre exploration systems, and for exploring large aesthetic parameter spaces more generally. Finally, we discuss how systems like SoundTraveller can fit into the existing workflows of electronic music composers, and how shared agency with creative technologies can impact the creative process.

Instructors facilitating online classes have a limited ability to see and hear interactions of student groups working in parallel, which prevents them from interacting with students effectively. In this work, we explore interface design for providing an overview of parallel group discussions in online classrooms. We derive design considerations through a participatory design process and instantiate them in our visualization interface, Groupnamics. Groupnamics visualizes recent vocal activities and discussion statuses of each group in a one-page view, facilitating identification of groups where intervention may be needed. Our user study with 16 instructors confirmed that Groupnamics can successfully provide cues for when instructors should join group discussions and improvements on the perceived usefulness and ease of use over the baseline interface representing existing videoconferencing tools. Our qualitative results suggest future research directions in interface design for online parallel group discussions.