“It’s Just a Wild, Wild West”: Harnessing Public Procurement as an AI Governance MechanismPublic sector AI has the potential to harm citizens, with risks increasing as its use expands. Recent work positions public procurement as a way to shape public sector AI in line with public interests, using the state’s purchasing power to influence which AI systems are procured and under what conditions. This paper examines how this potential can be realised in practice by drawing on semi-structured interviews with UK and EU buyers, providers, and procurement experts. Our findings result in six promising procurement practices that enable the public sector to shape AI in line with public interests, alongside concrete mechanisms to support their uptake. Further, we find that AI-specific procurement approaches remain immature and systems often enter through informal channels with less scrutiny. We provide directions for both research and practice on how public procurement can be used as a governance mechanism for better aligning AI with public interests.2026AHAnna Ida Hudig et al.University of CambridgeAI Ethics, Fairness & AccountabilityPrivacy by Design & User ControlAlgorithmic Fairness & BiasCHI
Determining Perception Thresholds for Real and Virtual Inclinations While Cycling in Virtual RealityIn virtual reality (VR) experiences, mismatches between reality and virtuality are usually undesirable, as they can disrupt immersion and induce cybersickness. However, when carefully controlled, they may expand the design space of VR. This research investigates perceptual detection thresholds for mismatches between real and virtual inclinations during cycling in VR. Using a custom simulation, N=30 participants cycled through a virtual city while physical and visual inclinations were independently manipulated. Real inclinations were implemented with a tilting indoor bike, providing vestibular and proprioceptive feedback, while virtual inclinations within the simulated environment were presented visually. A multiple staircase procedure derived estimates for perceptual thresholds that approximate which mismatches in visual and physical inclination were still perceived as congruent. These thresholds reveal a window of perceived congruence before mismatches become noticeable to users. These findings advance understanding of sensory integration in VR cycling and inform applications in immersive training, exergames, and rehabilitation systems.2026JKJonas Keppel et al.University of Duisburg-EssenImmersion & Presence ResearchFitness Tracking & Physical Activity MonitoringMotion Sickness & Passenger ExperienceCHI
Certified But Imperfect: Investigating The Role of AI Certifications And System Performance on Trust in And Reliance on AI SystemsWhile regulatory frameworks call for the implementation of AI certifications, empirical knowledge about how such certifications affect interactions is still scarce. In this work, we examined how AI certifications affect users' trust and reliance. In addition, we examined whether certifications elevate user expectations and whether unmet expectations subsequently reduce trust. In a 2 (certification vs no certification) x 2 (reliability: high vs low) between-subjects online study, N = 644 participants had to identify bacterial infestation in pictures with the help of an AI. Our results show that, before interacting with the AI, participants trusted the certified system more and showed reduced vigilance. However, these effects disappeared post-interaction, where, instead of the certification, system reliability significantly affected trust and vigilance. Notably, certifications did not raise expectations per se, but instead amplified the impact of system reliability on user trust. Additional exploratory results showed that the certification supported appropriate reliance.2026MWMagdalena Wischnewski et al.Research Center for Trustworthy Data Science and SecurityExplainable AI (XAI)Privacy by Design & User ControlAI-Assisted Decision-Making & AutomationCHI
The Limits of Stakeholder Participation in Safety-Critical Contexts: Lessons from Air Traffic ControlCalls for participatory AI development often assume that stakeholders can and should substantially shape a system's design. However, this agency may be constrained by competing demands, e.g. those safety-related. We explore this tension through a case study in Air Traffic Control (ATC) system development. Interviews with ATC operators and a focus group including R&D staff uncovered that operators’ input was confined to small changes, with major decisions made through opaque processes. Safety-related considerations often limited how operator input could be incorporated. Importantly, operators acknowledged that safety should take priority but called for more transparency over decision-making processes and the factors considered thereby. Our findings highlight how general calls for stakeholder empowerment can contradict safety-critical (and other) requirements. We show the importance of engaging broad perspectives to explore conflicting demands before aligning/prioritising these in the application context. We further outline implications for participatory practice relevant for responsible AI and HCI communities.2026EKEmma Marlene Kallina et al.UA Ruhr University Duisburg-EssenAI-Assisted Decision-Making & AutomationParticipatory DesignResearch Ethics & Open ScienceCHI
Certified AI System = Trustworthy? Exploring Expert and Lay User Perceptions and Needs Regarding AI CertificationAI certification has emerged as a promising mechanism to enhance transparency, accountability, and public trust. However, end-user perspectives remain largely unexplored. This study investigates two groups with differing AI expertise. Through qualitative interviews with 30 participants (15 experts, 15 lay users), we examined how AI certification influences trust, who should conduct it, transparency needs, post-certification monitoring, and certification fraud. Results reveal key differences between the two groups. Lay users perceive AI certification more positively than experts. Both groups prefer independent certifiers, with experts being more open to certification by private companies. Experts favor post-certification monitoring tied to system updates, whereas lay users prefer annual checks. Both groups value transparency, but the specific details they require differ. Regarding fraudulent AI certification, experts emphasize technical safeguards, while lay users focus on legal enforcement. The study discusses the implications of its findings and offers several recommendations for improving AI certification schemes.2026SGSarah Abdelwahab Gaballah et al.Ruhr University BochumExplainable AI (XAI)AI Ethics, Fairness & AccountabilityPrivacy by Design & User ControlCHI
Who Controls the Conversation? User Perspectives On Generative AI (LLM) System PromptsSystem prompts---instructions that shape the behaviour of generative AI systems---strongly influence system outputs and users' experiences. They define the model's guidelines, `personality', and guardrails, taking precedence over user inputs. Despite their influence, transparency is limited: system prompts are generally not made public and most platforms instruct models to conceal them, leaving users disconnected from and unaware of a key mechanism guiding and governing their AI interactions. This paper argues that system prompts warrant explicit, user-centred design attention and, focusing on large language models (LLMs), asks: what do system prompts contain, how do end-users perceive them, and what do these perceptions offer for design and governance practice? Our results reveal user perspectives on: the benefits and risks of system prompts; the values they prefer to be associated with prompt-design; their levels of comfort with different types of prompts; and degrees of transparency and user control regarding prompt content. From these findings emerge considerations for how designers can better align system prompt mechanisms with user expectations and preferences over these mechanisms that directly shape how generative AI systems behave.2026ANAnna Neumann et al.University Duisburg-EssenHuman-LLM CollaborationExplainable AI (XAI)AI Ethics, Fairness & AccountabilityCHI
Flow on Social Media? Rarer Than You'd ThinkResearchers often attribute social media’s appeal to its ability to elicit flow experiences of deep absorption and effortless engagement. Yet prolonged use has also been linked to distraction, fatigue, and lower mood. This paradox remains poorly understood, in part because prior studies rely on habitual or one-shot reports that ask participants to directly attribute flow to social media. To address this gap, we conducted a five-day field study with 40 participants, combining objective smartphone app tracking with daily reconstructions of flow-inducing activities. Across 673 reported flow occurrences, participants rarely associated flow with social media (2\%). Instead, heavier social media use predicted fewer daily flow occurrences. We further examine this relationship through the effects of social media use on fatigue, mood, and motivation. Altogether, our findings suggest that flow and social media may not align as closely as assumed - and might even compete - underscoring the need for further research.2026MKMichael T. Knierim et al.Karlsruhe Institute of Technology (KIT)Social Platform Design & User BehaviorCyberbullying & Online HarassmentEmpathy & Emotional DesignCHI
Campus AI vs. Commercial AI: Comparing How Students and Employees Perceive their University’s LLM Chatbot vs. ChatGPTAs the use of LLM chatbots by students and researchers becomes more prevalent, universities are pressed to develop AI strategies. One strategy that many universities pursue is to customize pre-trained LLM-as-a-service (LLMaaS) chatbots. While most studies on LLMaaS chatbots prioritize technical adaptations, these systems are often mainly characterized by user-salient front-end customizations, e.g., interface changes. Yet, no existing studies have examined how users perceive such systems compared to commercial LLM chatbots. In a field study, we investigate how students and employees (N = 526) at a German university perceive and use their institution's customized LLMaaS chatbot compared to ChatGPT. Participants using both systems (n = 116) reported greater trust, higher perceived privacy, and less perceived hallucinations with their university's customized LLMaaS chatbot compared to ChatGPT. We discuss implications for research on users' trustworthiness assessment process, and offer guidance for the design and deployment of LLMaaS chatbots.2026LHLeon Hannig et al.University of Duisburg-EssenHuman-LLM CollaborationExplainable AI (XAI)AI-Assisted Decision-Making & AutomationCHI
Simulating Multiple Road User Perspectives on Autonomous Vehicle BehaviorsThis work presents a system and a study in which we have multiple road users interact simultaneously with an autonomous vehicle (AV) in a virtual reality (VR) environment. We go beyond studying dyadic interactions (e.g., AV-pedestrian or AV-driver) to involve a pedestrian, a human driver, and an AV passenger all jointly interacting with an AV in the same VR scenario. We probed multiple user perspectives with two different prototypes of AV behavior strategies in ambiguous stop-sign intersections. An efficient AV attempts to enter the intersection as soon as it can without collision, while a prosocial AV waits for other road users to pass before proceeding. We recruited 16 three-person groups (N=48), where half interacted with the first AV type and the other half interacted with the second AV type in four different traffic configurations. Our investigation demonstrates that road users in different roles can have diverging preferences and trust levels in the same AV behavior when making joint decisions. Finally, we discuss how our methods and findings can be used to guide further explorations for AV interaction research with multiple agents in different roles.2025JJJiHyun Jeong et al.Automated Driving Interface & Takeover DesignExternal HMI (eHMI) — Communication with Pedestrians & CyclistsTeleoperated DrivingAutoUI
Shocking Realities: VR Horror Games as a Tool for Raising Wheelchair Accessibility AwarenessWheelchair users face numerous challenges in their daily lives, such as narrow hallways, stairs, or misplaced elevator buttons. While accessible design is important for addressing these issues in the long term, societal understanding and sensitization remain crucial for overcoming these daily obstacles. Our research aims to foster such awareness through virtual reality game design. In contrast to prior works, we intentionally avoid the didactic style typical of serious or persuasive games. Instead, we embed common wheelchair challenges within naturally fitting horror game mechanics. Insights from our playtest (N = 11) highlight the synergy between horror elements (e.g., loss of control, slowdown) and manual wheelchair locomotion challenges. Most importantly, this approach helped participants recognize the daily struggles faced by wheelchair users, demonstrating the potential of our method in promoting a more inclusive and understanding society.2025AKAndrey Krekhov et al.Accessible GamingUniversal & Inclusive DesignSerious & Functional GamesDIS
Situated Artifacts Amplify Engagement in Physical ActivityIn the context of rising sedentary lifestyles, this paper investigates the efficacy of "Situated Artifacts" in promoting physical activity. We designed two artifacts that display users' physical activity data within their homes - one physical and one digital. We conducted a 9-week, counterbalanced, within-subject field study with N=24 participants to assess the impact of these artifacts on physical activity, reflection, and motivation. We collected quantitative data on physical activity and administered daily and weekly questionnaires, employing individual Likert items and standardized instruments, as well as conducted interviews post-prototype usage. Our findings indicate that while both artifacts act as reminders for physical activity, the physical artifact was superior in terms of user engagement. The study revealed that this can be attributed to the higher perceived presence and, thereby, enhanced social interaction, which acts as a motivational source for activity. In this sense, situated artifacts gently nudge toward sustainable health behavior change.2025JKJonas Keppel et al.Fitness Tracking & Physical Activity MonitoringSleep & Stress MonitoringDIS
How To Draw Commands? An Elicitation Study for Sketching on SpreadsheetsSketching is one of the oldest techniques humans use to express themselves. We sketch to visualize concepts, externalize memory, and communicate ideas. However, we barely use sketching to interact with computers. Given how naturally sketching comes to humans, we believe untapped potential exists in being able to simply draw commands onto a user interface. In this paper, we present results of an elicitation study about expressing common operations in spreadsheets through sketching. Spreadsheets are an interesting class of applications because they are widely used, support complex data and operations, and are available on touch-enabled devices. Our results show that despite considerable variation in syntactic details, participants gravitate towards recurring patterns (\eg\ enclosures and arrows, examples and cross-references, and temporal sequences of strokes). The sketch patterns we identified can be a first step towards developing interpreters of sketched commands, and thus enable new means of interacting with spreadsheets and other applications.2025MHMarc Hesenius et al.University of Duisburg-EssenPrototyping & User TestingComputational Methods in HCICHI
A Pandemic for the Good of Digital Literacy? An Empirical Investigation of Newly Improved Digital Skills during COVID-19 LockdownsThis research explores whether the rapid digital transformation due to COVID-19 managed to close or exacerbate the digital divide concerning users’ digital skills. We conducted a pre-registered survey with N = 1,143 German Internet users. Our findings suggest the latter: younger, male, and higher educated users were more likely to improve their digital skills than older, female, and less educated ones. According to their accounts, the pandemic helped Internet users improve their skills in communicating with others by using video conference software and reflecting critically upon information they found online. These improved digital skills exacerbated not only positive (e.g., feeling informed and safe) but also negative (e.g., feeling lonely) effects of digital media use during the pandemic. We discuss this research's theoretical and practical implications regarding the impact of challenges, such as technological disruption and health crises, on humans’ digital skills, capabilities, and future potential, focusing on the second-level digital divide.2025GNGerman Neubaum et al.University of Duisburg-EssenUser Research Methods (Interviews, Surveys, Observation)Sustainable HCICHI
Long-Term Effects of User Expertise and Application Design on Collision Anxiety in VR GamesVirtual reality (VR) applications achieve their high immersive potential by detaching the user from the real world, replacing it through a virtual environment. This detachment also blocks real-world orientation cues, which might cause fear of colliding with the real environment and negatively impact the player experience. However, since collision anxiety (CA) is a relatively young concept, it is unclear how factors like users’ VR expertise or specific game design choices may affect it. We defined expected CA profiles for five commercial VR games and conducted a longitudinal study examining how growing VR expertise and VR game design influence the users’ CA. After six weeks and a total of 154 VR sessions, results indicate that CA differs between applications and generally decreases as VR expertise increases. Based on our results, we propose design implications, providing researchers and designers with guidelines on when to expect and how to avoid fear of colliding.2025PRPatrizia Ring et al.Faculty of Computer Science / Department of Human-centered Computing and Cognitive Science (HCCS) / Entertainment Computing GroupImmersion & Presence ResearchGame UX & Player BehaviorCHI
Virtual Visits, Real Emotions: Designing Social VR Experiences for Imprisoned Fathers and their ChildrenThe imprisonment of parents has severe consequences for their relationship to their children. Thus, ensuring valuable contact between them is crucial for parent’s social rehabilitation and children’s development and well-being. However, visits are often not child-friendly and lack interaction. We see social VR as a means to address these issues. In this paper, we share findings of a user-centered design process of a virtual reality application that allows imprisoned parents to meet their children. Our pilot study with four dyads of children and imprisoned fathers revealed that both appreciated the virtual visits, felt close to each other, and had a positive emotional experience, although fathers missed physical contact. Children preferred VR’s playful and interactive nature compared to regular visits. Our research presents virtual visits as a suitable alternative to ensure valuable social interaction between prisoners and their children and contribute to the potential of immersive virtual social experiences for sensitive use cases.2025LGLinda Graf et al.University of Duisburg-Essen, Faculty of Computer Science / Department of Human-centered Computing and Cognitive Science (HCCS) / Entertainment Computing Group/Social & Collaborative VRImmersion & Presence ResearchIdentity & Avatars in XRCHI
Spatial Haptics: A Sensory Substitution Method for Distal Object Detection Using Tactile CuesWe present a sensory substitution-based method for representing locations of remote objects in 3D space via haptics. By imitating auditory localization processes, we enable vibrotactile localization abilities similar to those of some spiders, elephants, and other species. We evaluated this concept in virtual reality by modulating the vibration amplitude of two controllers depending on relative locations to a target. We developed two implementations applying this method using either ear or hand locations. A proof-of-concept study assessed localization performance and user experience, achieving under 30° differentiation between horizontal targets with no prior training. This unique approach enables localization by using only two actuators, requires low computational power, and could potentially assist users in gaining spatial awareness in challenging environments. We compare the implementations and discuss the use of hands as ears in motion, a novel technique not previously explored in the sensory substitution literature.2025IWIddo Yehoshua Wald et al.University of Bremen, Digital Media LabVibrotactile Feedback & Skin StimulationFull-Body Interaction & Embodied InputCHI
OptiBasePen: Mobile Base+Pen Input on Passive Surfaces by Sensing Relative Base Motion Plus Close-Range Pen PositionDigital pen input devices based on absolute pen position sensing, such as Wacom Pens, support high-fidelity pen input. However, they require specialized sensing surfaces like drawing tablets, which can have a large desk footprint, constrain the possible input area, and limit mobility. In contrast, digital pens with integrated relative sensing enable mobile use on passive surfaces, but suffer from motion artifacts or require surface contact at all times, deviating from natural pen affordances. We present OptiBasePen, a device for mobile pen input on ordinary surfaces. Our prototype consists of two parts: the "base" on which the hand rests and the pen for fine-grained input. The base features a high-precision mouse sensor to sense its own relative motion, and two infrared image sensors to track the absolute pen tip position within the base's frame of reference. This enables pen input on ordinary surfaces without external cameras while also avoiding drift from pen micro-movements. In this work, we present our prototype as well as the general base+pen concept, which combines relative and absolute sensing.2024AFAndreas Rene Fender et al.Circuit Making & Hardware PrototypingKnowledge Worker Tools & WorkflowsUIST
Understanding the Impact of the Reality-Virtuality Continuum on Visual Search using Physiological MeasuresWhile Mixed Reality allows the seamless blending of digital content in their surroundings, it is not clear if such a fusion of digital and physical information impacts users' perceptual and cognitive resources differently. While the fusion of real and virtual objects provides numerous opportunities to present additional information, it also introduces undesirable side effects, such as split attention and increased visual complexity. We conducted a visual search study in three manifestations of mixed reality to understand the effects of the environment on visual search behavior. We conducted a multimodal evaluation using EEG and eye-tracking correlates of search efficiency, distractor suppression, attention allocation, and behavioral measures. We found that, independently of the perceptual load, Augmented Reality environments reduce users' capacity to identify target information and suppress irrelevant stimuli. Participants reported AR as more demanding and distracting. We discuss design implications for MR interfaces based on physiological inputs for adaptive interactions.2024FCFrancesco Chiossi et al.Eye Tracking & Gaze InteractionBrain-Computer Interface (BCI) & NeurofeedbackAR Navigation & Context AwarenessMobileHCI
Understanding User Acceptance of Electrical Muscle Stimulation in Human-Computer InteractionElectrical Muscle Stimulation (EMS) has unique capabilities that can manipulate users' actions or perceptions, such as actuating user movement while walking, changing the perceived texture of food, and guiding movements for a user learning an instrument. These applications highlight the potential utility of EMS, but such benefits may be lost if users reject EMS. To investigate user acceptance of EMS, we conducted an online survey (N=101). We compared eight scenarios, six from HCI research applications and two from the sports and health domain. To gain further insights, we conducted in-depth interviews with a subset of the survey respondents (N=10). The results point to the challenges and potential of EMS regarding social and technological acceptance, showing that there is greater acceptance of applications that manipulate action than those that manipulate perception. The interviews revealed safety concerns and user expectations for the design and functionality of future EMS applications.2024SFSarah Faltaous et al.University Duisburg-EssenElectrical Muscle Stimulation (EMS)CHI
Kinetic Signatures: A Systematic Investigation of Movement-Based User Identification in Virtual RealityBehavioral Biometrics in Virtual Reality (VR) enable implicit user identification by leveraging the motion data of users' heads and hands from their interactions in VR. This spatiotemporal data forms a Kinetic Signature, which is a user-dependent behavioral biometric trait. Although kinetic signatures have been widely used in recent research, the factors contributing to their degree of identifiability remain mostly unexplored. Drawing from existing literature, this work systematically examines the influence of static and dynamic components in human motion. We conducted a user study (N = 24) with two sessions to reidentify users across different VR sports and exercises after one week. We found that the identifiability of a kinetic signature depends on its inherent static and dynamic factors, with the best combination allowing for 90.91 % identification accuracy after one week had passed. Therefore, this work lays a foundation for designing and refining movement-based identification protocols in immersive environments.2024JLJonathan Liebers et al.University of Duisburg-EssenEye Tracking & Gaze InteractionHuman Pose & Activity RecognitionSocial & Collaborative VRCHI