A Comparative Study of How People With and Without ADHD Recognise and Avoid Dark Patterns on Social MediaDark patterns are deceptive strategies that recent work in human-computer interaction (HCI) has captured throughout digital domains, including social networking sites (SNSs). While research has identified difficulties among people to recognise dark patterns effectively, few studies consider vulnerable populations and their experience in this regard, including people with attention deficit hyperactivity disorder (ADHD), who may be especially susceptible to attention-grabbing tricks. Based on an interactive web study with 135 participants, we investigate SNS users' ability to recognise and avoid dark patterns by comparing results from participants with and without ADHD. In line with prior work, we noticed overall low recognition of dark patterns with no significant differences between the two groups. Yet, ADHD individuals were able to avoid specific dark patterns more often. Our results advance previous work by understanding dark patterns in a realistic environment and offer insights into their effect on vulnerable populations.2025TMThomas Mildner et al.University of BremenCognitive Impairment & Neurodiversity (Autism, ADHD, Dyslexia)Dark Patterns RecognitionCHI
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
Listening to the Voices: Describing Ethical Caveats of Conversational User Interfaces According to Experts and Frequent UsersAdvances in natural language processing and understanding have led to a rapid growth in the popularity of conversational user interfaces (CUIs). While CUIs introduce novel benefits, they also yield risks that may exploit people's trust. Although research looking at unethical design deployed through graphical user interfaces (GUIs) established a thorough taxonomy of so-called dark patterns, there is a need for an equally in-depth understanding in the context of CUIs. Addressing this gap, we interviewed 27 participants from three cohorts: researchers, practitioners, and frequent users of CUIs. Applying thematic analysis, we develop five themes reflecting each cohort's insights about ethical design challenges and introduce the CUI Expectation Cycle, bridging system capabilities and user expectations while respecting each theme's ethical caveats. This research aims to inform future work to consider ethical constraints while adopting a human-centred approach.2024TMThomas Mildner et al.University of BremenVoice User Interface (VUI) DesignAI Ethics, Fairness & AccountabilityDark Patterns RecognitionCHI
"I Know What You Mean": Context-Aware Recognition to Enhance Speech-Based GamesRecent advances in language processing and speech recognition open up a large opportunity for video game companies to embrace voice interaction as an intuitive feature and appealing game mechanics. However, speech-based systems still remain liable to recognition errors. These add a layer of challenge on top of the game's existing obstacles, preventing players from reaching their goals and thus often resulting in player frustration. This work investigates a novel method called context-aware speech recognition, where the game environment and actions are used as supplementary information to enhance recognition in a speech-based game. In a between-subject user study (N=40), we compared our proposed method with a standard method in which recognition is based only on the voice input without taking context into account. Our results indicate that our proposed method could improve the player experience and the usability of the speech system.2024NZNima Zargham et al.University of BremenVoice User Interface (VUI) DesignGame UX & Player BehaviorCHI
Defending Against the Dark Arts: Recognising Dark Patterns in Social MediaInterest in unethical user interfaces has grown in HCI over recent years, with researchers identifying malicious design strategies referred to as "dark patterns". While such strategies have been described in numerous domains, we lack a thorough understanding of how they operate in social networking services (SNSs). Pivoting towards regulations against such practices, we address this gap by offering novel insights into the types of dark patterns deployed in SNSs and people's ability to recognise them across four widely used mobile SNS applications. Following a cognitive walkthrough, experts (N=6) could identify instances of dark patterns in all four SNSs, including co-occurrences. Based on the results, we designed a novel rating procedure for evaluating the malice of interfaces. Our evaluation shows that regular users (N=193) could differentiate between interfaces featuring dark patterns and those without. Such rating procedures could support policymakers' current moves to regulate deceptive and manipulative designs in online interfaces.2023TMThomas Mildner et al.Dark Patterns RecognitionSocial Platform Design & User BehaviorDIS
About Engaging and Governing Strategies: A Thematic Analysis of Dark Patterns in Social Networking ServicesResearch in HCI has shown a growing interest in unethical design practices across numerous domains, often referred to as ``dark patterns''. There is, however, a gap in related literature regarding social networking services (SNSs). In this context, studies emphasise a lack of users' self-determination regarding control over personal data and time spent on SNSs. We collected over 16 hours of screen recordings from Facebook's, Instagram's, TikTok's, and Twitter's mobile applications to understand how dark patterns manifest in these SNSs. For this task, we turned towards HCI experts to mitigate possible difficulties of non-expert participants in recognising dark patterns, as prior studies have noticed. Supported by the recordings, two authors of this paper conducted a thematic analysis based on previously described taxonomies, manually classifying the recorded material while delivering two key findings: We observed which instances occur in SNSs and identified two strategies – engaging and governing – with five dark patterns undiscovered before.2023TMThomas Mildner et al.University of Bremen, University of BremenDark Patterns RecognitionSocial Platform Design & User BehaviorCHI
Haptic Fidelity Framework: Defining the Factors of Realistic Haptic Feedback for Virtual RealityProviding haptic feedback in virtual reality to make the experience more realistic has become a strong focus of research in recent years. The resulting haptic feedback systems differ greatly in their technologies, feedback possibilities, and overall realism making it challenging to compare different systems. We propose the Haptic Fidelity Framework providing the means to describe, understand and compare haptic feedback systems. The framework locates a system in the spectrum of providing realistic or abstract haptic feedback using the Haptic Fidelity dimension. It comprises 14 criteria that either describe foundational or limiting factors. A second Versatility dimension captures the current trade-off between highly realistic but application-specific and more abstract but widely applicable feedback. To validate the framework, we compared the Haptic Fidelity score to the perceived feedback realism of evaluations from 38 papers and found a strong correlation suggesting the framework accurately describes the realism of haptic feedback.2022TMThomas Muender et al.University of BremenMid-Air Haptics (Ultrasonic)Vibrotactile Feedback & Skin StimulationCHI
"I Didn't Catch That, But I'll Try My Best": Anticipatory Error Handling in a Voice Controlled Game Advances in speech recognition, language processing and natural interaction have led to an increased industrial and academic interest. While the robustness and usability of such systems are steadily increasing, speech-based systems are still susceptible to recognition errors. This makes intelligent error handling of utmost importance for the success of those systems. In this work, we integrated anticipatory error handling for a voice-controlled video game where the game would perform a locally optimized action in respect to goal completion and obstacle avoidance, when a command is not recognized. We evaluated the user experience of our approach versus traditional, repetition-based error handling (N = 34). Our results indicate that implementing anticipatory error handling can improve the usability of a system, if it follows the intention of the user. Otherwise, it impairs the user experience, even when deciding for technically optimal decisions.2022NZNima Zargham et al.University of BremenVoice User Interface (VUI) DesignGame UX & Player BehaviorCHI
Serious Snacking: A Survival Analysis of how Snacking Mechanics Affect Attrition in a Mobile Serious GameMany serious games are most effective when played regularly; however, little is known about how individual game elements support player adherence over time. This work draws on evidence from existing frameworks and game design theories as well as from the design of casual games to investigate how individual game mechanics affect player attrition in a serious game. We implemented a math-learning game in which we could individually layer various game mechanics, and over the course of 3 weeks, 99 participants played one of six versions: Baseline, Rewards, Novelty, Completion, Waiting, or Blocking. We compared the game versions by analyzing the players' performance as well as behaviour. Using survival analysis, we identified that the addition of Completion and Blocking mechanics facilitated the strongest sustained engagement. These findings are congruent with existing theories of player experience and promote the development of guidelines on designing for sustained engagement in serious games.2021DADmitry Alexandrovsky et al.University of BremenSerious & Functional GamesGamification DesignCHI
Breaking The Experience: Effects of Questionnaires in VR User StudiesQuestionnaires are among the most common research tools in virtual reality (VR) evaluations and user studies. However, transitioning from virtual worlds to the physical world to respond to VR experience questionnaires can potentially lead to systematic biases. Administering questionnaires in VR (inVRQs) is becoming more common in contemporary research. This is based on the intuitive notion that inVRQs may ease participation, reduce the Break in Presence (BIP) and avoid biases. In this paper, we perform a systematic investigation into the effects of interrupting the VR experience through questionnaires using physiological data as a continuous and objective measure of presence. In a user study (n=50), we evaluated question-asking procedures using a VR shooter with two different levels of immersion. The users rated their player experience with a questionnaire either inside or outside of VR. Our results indicate a reduced BIP for the employed inVRQ without affecting the self-reported player experience.2020SPSusanne Putze et al.University of BremenImmersion & Presence ResearchCHI
Bot or not? User Perceptions of Player Substitution with Deep Player Behavior ModelsMany online games suffer when players drop off due to lost connections or quitting prematurely, which leads to match terminations or game-play imbalances. While rule-based outcome evaluations or substitutions with bots are frequently used to mitigate such disruptions, these techniques are often perceived as unsatisfactory. Deep learning methods have successfully been used in deep player behavior modelling (DPBM) to produce non-player characters or bots which show more complex behavior patterns than those modelled using traditional AI techniques. Motivated by these findings, we present an investigation of the player-perceived awareness, believability and representativeness, when substituting disconnected players with DPBM agents in an online-multiplayer action game. Both quantitative and qualitative outcomes indicate that DPBM agent substitutes perform similarly to human players and that players were unable to detect substitutions. Notably, players were in fact able to detect substitution with agents driven by more traditional heuristics.2020JPJohannes Pfau et al.University of BremenGame UX & Player BehaviorSerious & Functional GamesCHI
Examining Design Choices of Questionnaires in VR User StudiesQuestionnaires are among the most common research tools in virtual reality (VR) user studies. Transitioning from virtuality to reality for giving self-reports on VR experiences can lead to systematic biases. VR allows to embed questionnaires into the virtual environment which may ease participation and avoid biases. To provide a cohesive picture of methods and design choices for questionnaires in VR (inVRQ), we discuss 15 inVRQ studies from the literature and present a survey with 67 VR experts from academia and industry. Based on the outcomes, we conducted two user studies in which we tested different presentation and interaction methods of inVRQs and evaluated the usability and practicality of our design. We observed comparable completion times between inVRQs and questionnaires outside VR (nonVRQs) with higher enjoyment but lower usability for \inVRQs. These findings advocate the application of inVRQs and provide an overview of methods and considerations that lay the groundwork for inVRQ design.2020DADmitry Alexandrovsky et al.University of BremenImmersion & Presence ResearchUser Research Methods (Interviews, Surveys, Observation)Prototyping & User TestingCHI
Enemy Within: Long-term Motivation Effects of Deep Player Behavior Models for Dynamic Difficulty AdjustmentBalancing games and producing content that remains interesting and challenging is a main cost factor in the design and maintenance of games. Dynamic difficulty adjustments (DDA) can successfully tune challenge levels to player abilities, but when implemented with classic heuristic parameter tuning (HPT) often turns out to be very noticeable, e.g. as "rubber-banding". Deep learning techniques can be employed for deep player behavior modeling (DPBM), enabling more complex adaptivity, but effects over frequent and longer-lasting game engagements, as well as how it compares to HPT has not been empirically investigated. We present a situated study of the effects of DDA via DPBM as compared to HPT on intrinsic motivation, perceived challenge and player motivation in a real-world MMORPG. The results indicate that DPBM can lead to significant improvements in intrinsic motivation and players prefer game experience episodes featuring DPBM over experience episodes with classic difficulty management.2020JPJohannes Pfau et al.University of BremenGame UX & Player BehaviorSerious & Functional GamesGamification DesignCHI
Does It Feel Real? Using Tangibles with Different Fidelities to Build and Explore Scenes in Virtual RealityProfessionals in domains like film, theater, or architecture often rely on physical models to visualize spaces. With virtual reality (VR) new tools are available providing immersive experiences with correct perceptions of depth and scale. However, these lack the tangibility of physical models. Using tangible objects in VR can close this gap but creates the challenges of producing suitable objects and interacting with them with only the virtual objects visible. This work addresses these challenges by evaluating tangibles with three haptic fidelities: equal disc-shaped tangibles for all virtual objects, Lego-built tangibles, and 3D-printed tangibles resembling the virtual shapes. We present results from a comparative study on immersion, performance, and intuitive interaction and interviews with domain experts. The results show that 3D-printed objects perform best, but Lego offers a good trade-off between fast creation of tangibles and sufficient fidelity. The experts rate our approach as useful and would use all three versions.2019TMThomas Muender et al.University of BremenMixed Reality WorkspacesImmersion & Presence Research3D Modeling & AnimationCHI
The Role of Physical Props in VR Climbing EnvironmentsDealing with fear of falling is a challenge in sport climbing. Virtual reality (VR) research suggests that using physical and reality-based interaction increases the presence in VR. In this paper, we present a study that investigates the influence of physical props on presence, stress and anxiety in a VR climbing environment involving whole body movement. To help climbers overcoming fear of falling, we compared three different conditions: Climbing in reality at 10 m height, physical climbing in VR (with props attached to the climbing wall) and virtual climbing in VR using game controllers. From subjective reports and biosignals, our results show that climbing with props in VR increases the anxiety and sense of realism in VR for sport climbing. This suggests that VR in combination with physical props are an effective simulation setup to induce the sense of height.2019PSPeter Schulz et al.University of BremenFull-Body Interaction & Embodied InputImmersion & Presence ResearchCHI
Insert Needle Here! A Custom Display for Optimized Biopsy Needle PlacementNeedle-guiding templates are used for a variety of minimally invasive medical interventions. While physically supporting needle placement with a grid of holes, they lack integrated information where needles need to be inserted. Physicians must manually determine the correct holes based on the output of planning software - a workflow that is error-prone and lengthy. We address these issues by embedding a display into the template using electroluminescence (EL) screen printing. The EL display is connected to planning software and illuminates the correct hole. In an empirical evaluation with physicians and researchers from the medical domain, we compare the illuminated against the conventional template as used in magnetic resonance imaging (MRI) guided prostate biopsies. Our results show that the EL display significantly improves task completion time by 51 %, task load by 47 % and usability by 30 %.2018ARAnke Verena Reinschluessel et al.University of BremenFitness Tracking & Physical Activity MonitoringSurgical Assistance & Medical TrainingCHI