Human-Computer Interaction at TU Darmstadt
We are a collective of the following labs:
Telecooperation Lab |
HCI Lab |
Urban Interaction Lab |
PEASEC |
FAI |
SEEMOO
ABSTRACT - With the increasing spread of AR head-mounted displays for everyday use, interaction with information becomes ubiquitous, even while walking, requiring constant attention shifts between walking and virtual interaction; thus, we systematically investigate the effects of different AR anchors (hand, head, torso) and task difficulties on user experience and performance through a dual-task paradigm with 26 participants, assessing virtual and walking performance as well as mental and physical load, finding that head-anchored AR content least affected walking while enabling fast and accurate interaction, whereas hand-anchored content increased reaction times and workload.
ABSTRACT - Generative AI in Virtual Reality offers the potential for collaborative object-building, yet challenges remain in aligning AI contributions with user expectations. In particular, users often struggle to understand and collaborate with AI when its actions are not transparently represented. This paper thus explores the co-creative object-building process through a Wizard-of-Oz study, focusing on how AI can effectively convey its intent to users during object customization in Virtual Reality. Inspired by human-to-human collaboration, we focus on three representation modes: the presence of an embodied avatar, whether the AI’s contributions are visualized immediately or incrementally, and whether the areas modified are highlighted in advance. The findings provide insights into how these factors affect user perception and interaction with object-generating AI tools in Virtual Reality as well as satisfaction and ownership of the created objects. The results offer design implications for co-creative world-building systems, aiming to foster more effective and satisfying collaborations between humans and AI in Virtual Reality.
ABSTRACT - Youth are particularly likely to encounter hateful internet content, which can severely impact their well-being. While most social media provide reporting mechanisms, in several countries, severe hateful content can alternatively be reported to law enforcement or dedicated reporting centers. However, in Germany, many youth never resort to reporting. While research in human-computer interaction has investigated adults’ views on platform-based reporting, youth perspectives and platform-independent alternatives have received little attention. By involving a diverse group of 47 German adolescents and young adults in eight focus group interviews, we investigate how youth-sensitive reporting systems for hateful content can be designed. We explore German youth’s reporting barriers, finding that on platforms, they feel particularly discouraged by deficient rule enforcement and feedback, while platform-independent alternatives are rather unknown and perceived as time-consuming and disruptive. We further elicit their requirements for platform-independent reporting tools and contribute with heuristics for designing youth-sensitive and inclusive reporting systems.
ABSTRACT - In light of the increasing vulnerability of citizens against cyberattacks, we conducted three representative surveys with German citizens in 2021 (N=1,093), 2023 (N=1,011), and 2024 (N=1,004) to examine their cyber threat awareness, use of protective security measures, and preferred information channels. While our findings attest large proportions of the German population a high level of cyber threat awareness, many citizens feel inadequately informed about coping with cyberattacks and show little confidence in German security authorities to protect citizens and infrastructures. While age correlated with citizens’ awareness and behavior, we only saw minor temporal differences between datasets. Finally, we provide design and policy implications for enhancing citizens’ awareness of cyber threats and implementing security measures.
ABSTRACT - Research in Augmented Reality (AR) and Virtual Reality (VR) has mostly viewed them in isolation. Yet, when used together in practical settings, AR and VR each offer unique strengths, necessitating multiple transitions to harness their advantages. This paper investigates potential challenges in Cross-Reality (CR) transitions to inform future application design. We implemented a CR system featuring a 3D modeling task that requires users to switch between PC, AR, and VR. Using a talk-aloud study (n=12) and thematic analysis, we revealed that frictions primarily arose when transitions conflicted with users’ Spatial Mental Model (SMM). Furthermore, we found five transition archetypes employed to enhance productivity once an SMM was established. Our findings uncover that transitions have to focus on establishing and upholding the SMM of users across realities by communicating differences between them.
ABSTRACT - Using smartphone apps during crises is well-established, proving critical for efficient crisis response; however, such apps become futile without an Internet connection, a common issue during crises. The ongoing 6G standardization explores the capability to provide local cellular connectivity for areas cut off from the Internet in crises. This paper introduces to the HCI community the concept of cellular island connectivity in isolated areas, promising a seamless transition from normal operation to island operation with local-only cellular connectivity. It presents findings from a survey (𝑁 = 857) among adult smartphone users from major German cities regarding their smartphone usage preferences in this model. Results show a shift in app demand, with users favoring general-purpose apps over dedicated crisis apps in specific scenarios. We prioritize smartphone services based on their criticality, distinguishing between apps essential for crisis response and those supporting routines. Our findings provide operators, developers, and authorities insights into making user-centric design decisions for implementing island-ready 6G communication.
ABSTRACT - With the recent advancements in Large Language Models (LLMs), web developers increasingly apply their code-generation capabilities to website design; however, since these models are trained on existing designerly knowledge, they may inadvertently replicate bad or even illegal practices, especially deceptive designs (DD). This paper examines whether users can accidentally create DD for a fictitious webshop using GPT-4. We recruited 20 participants, asking them to use ChatGPT to generate functionalities (product overview or checkout) and then modify these using neutral prompts to meet a business goal (e.g., “increase the likelihood of us selling our product”). We found that all 20 generated websites contained at least one DD pattern (mean: 5, max: 9), with GPT-4 providing no warnings. When reflecting on the designs, only 4 participants expressed concerns, while most considered the outcomes satisfactory and not morally problematic, despite the potential ethical and legal implications for end-users and those adopting ChatGPT’s recommendations.
ABSTRACT - Dark Patterns are deceptive designs that influence a user's interactions with an interface to benefit someone other than the user. Prior work has identified dark patterns in WIMP interfaces and ubicomp environments, but how dark patterns can manifest in Augmented and Virtual Reality (collectively XR) requires more attention. We therefore conducted ten co-design workshops with 20 experts in XR and deceptive design. Our participants co-designed 42 scenarios containing dark patterns, based on application archetypes presented in recent HCI/XR literature. In the co-designed scenarios, we identified ten novel dark patterns in addition to 39 existing ones, as well as ten examples in which specific characteristics associated with XR potentially amplified the effect dark patterns could have on users. Based on our findings and prior work, we present a classification of XR-specific properties that facilitate dark patterns: perception, spatiality, physical/virtual barriers, and XR device sensing. We also present the experts’ assessments of the likelihood and severity of the co-designed scenarios and highlight key aspects they considered for this evaluation, for example, technological feasibility, ease of upscaling and distributing malicious implementations, and the application's context of use. Finally, we discuss means to mitigate XR dark patterns and support regulatory bodies to reduce potential harms.
ABSTRACT - Perceptual manipulations (PMs) like redirected walking (RDW) are frequently applied in Virtual Reality (VR) to overcome technological limitations; these PMs manipulate the user’s visual perceptions (e.g., rotational gains), which is currently challenging in Augmented Reality (AR). We propose SwitchAR, a PM for video pass-through AR leveraging change and inattentional blindness to imperceptibly switch between the camera stream of the real environment and a 3D reconstruction, enabling VR redirection techniques in what users still perceive as AR. We present our pipeline consisting of (1) Reconstruction, (2) Switch (AR -> VR), (3) PM, and (4) Switch (VR -> AR), together with a prototype implementing this pipeline, establishing SwitchAR as a fundamental basis for enabling AR PMs.
ABSTRACT - Many EU data collectors rely on informed consent for data processing, requiring users to consent after being informed, which necessitates users having at least partially correct assumptions about the software's functionality. The introduction of Germany’s contact tracing app, the Corona-Warn-App (CWA), provides a case to explore whether potential users can be sufficiently informed with reasonable effort by software publishers. Through interviews (N=20) and a survey (N=352), we captured CWA users’ and non-users’ mental models of data collection and processing, finding that participants had misconceptions. We argue that user consent often lacks the required level of informedness and may need to be replaced by a more rigorous privacy-by-design principle.
ABSTRACT - Computer Emergency Response Teams (CERTs) have been established in the public sector globally to provide advisory, preventive and reactive cybersecurity services for government agencies, citizens, and businesses. Nevertheless, their responsibility of monitoring, analyzing, and communicating cyber threats and security vulnerabilities have become increasingly challenging due to the growing volume and varying quality of information disseminated through public and social channels. Based on a design case study conducted from 2021 to 2023, this paper combines three iterations of expert interviews (N=25), design workshops (N=4) and cognitive walkthroughs (N=25) to design an automated, cross-platform and real-time cybersecurity dashboard. By adopting the notion of cyber situational awareness, the study further extracts user requirements and design heuristics for enhanced threat intelligence and mission awareness in CERTs, discussing the aspects of source integration, data management, customizable visualization, relationship awareness, information assessment, software integration, (inter-)organizational collaboration, and communication of stakeholder warnings.
ABSTRACT - Misinformation poses a recurrent challenge for video-sharing platforms (VSPs) like TikTok. Obtaining user perspectives on digital interventions addressing the need for transparency (e.g., through indicators) is essential. This article offers a thorough examination of the comprehensibility, usefulness, and limitations of an indicator-based intervention from an adolescents’ perspective. This study (𝑁 = 39; aged 13-16 years) comprised two qualitative steps: (1) focus group discussions and (2) think-aloud sessions, where participants engaged with a smartphone-app for TikTok. The results offer new insights into how video-based indicators can assist adolescents' assessments. The intervention received positive feedback, especially for its transparency, and could be applicable to new content. This paper sheds light on how adolescents are expected to be experts while also being prone to video-based misinformation, with limited understanding of an interventions's limitations. by adopting teenagers' perspectives, we contribute to HCI research and provide new insights into the chances and limitations of interventions for VSPs.
ABSTRACT - Amidst the ongoing anti-military protests in Myanmar since 2021, there is a noticeable research gap on ICT-supported activism. Generally, ICTs play an important role during political crises in conjunction with activists’ practices on the ground. Inspired by Resource Mobilization Theory, I conducted qualitative interviews (N=16) and a qualitative online survey (N=34), which demonstrate the intersection between analog and digital domains, showcasing the ingenuity of the activists, and the rapid adoption of ICTs in a country that has experienced a digital revolution within the last few years. As not all people were able to protest on-the-ground, they acted as keyboard fighters to organize protests, to share information, and to support the civil disobedience movement in Myanmar. The study identifies, inter alia, the need for better offline applications with wider coverage in times of internet shutdowns, applications that cannot be easily identified during physical controls, and providing free and secure VPN access.
ABSTRACT - Advancements in haptics for Virtual Reality (VR) increased the quality of immersive content. Particularly, recent efforts to provide realistic temperature sensations have gained traction, but most often require very specialized or large complex devices to create precise thermal actuations. However, being largely detached from the real world, such a precise correspondence between the physical location of thermal stimuli and the shown visuals in VR might not be necessary for an authentic experience. In this work, we contribute the findings of a controlled experiment with 20 participants, investigating the spatial localization accuracy of thermal stimuli while having matching and non-matching visual cues of a virtual heat source in VR. Although participants were highly confident in their localization decisions, their ability to accurately pinpoint thermal stimuli was notably deficient.
ABSTRACT - Source confusion occurs when individuals attribute a memory to the wrong source (e.g., confusing a picture with an experienced event). Virtual Reality (VR) represents a new source of memories particularly prone to being confused with reality. While previous research identified causes of source confusion between reality and other sources (e.g., imagination, pictures), there is currently no understanding of what characteristics specific to VR (e.g., immersion, presence) could influence source confusion. Through a laboratory study (n=29), we 1) confirm the existence of VR source confusion with current technology, and 2) present a quantitative and qualitative exploration of factors influencing VR source confusion. Building on the Source Monitoring Framework, we identify VR characteristics and assumptions about VR capabilities (e.g., poor rendering) that are used to distinguish virtual from real memories. From these insights, we reflect on how the increasing realism of VR could leave users vulnerable to memory errors and perceptual manipulations.
ABSTRACT - Extended Reality (XR) allows in-situ previewing of designs to be manufactured through Personal Fabrication (PF). These in-situ interactions exhibit advantages for PF, like incorporating the environment into the design process. However, design-for-fabrication in XR often happens through either highly complex 3D-modeling or is reduced to rudimentary adaptations of crowd-sourced models. We present pARam, a tool combining parametric designs (PDs) and XR, enabling in-situ configuration of artifacts for PF. In contrast to modeling- or search-focused approaches, pARam supports customization through embodied and practical inputs (e.g., gestures, recommendations) and evaluation (e.g., lighting estimation) without demanding complex 3D-modeling skills. We implemented pARam for HoloLens 2 and evaluated it (n=20), comparing XR and desktop conditions. Users succeeded in choosing context-related parameters and took their environment into account for their configuration using pARam. We reflect on the prospects and challenges of PDs in XR to streamline complex design methods for PF while retaining suitable expressivity.
ABSTRACT - Hybrid board games (HBGs) augment their analog origins digitally (e.g., through apps) and are an increasingly popular pastime activity. Continuous world and character development and customization, known to facilitate engagement in video games, remain rare in HBGs. If present, they happen digitally or imaginarily, often leaving physical aspects generic. We developed DungeonMaker, a fabrication-augmented HBG bridging physical and digital game elements: 1) the setup narrates a story and projects a digital game board onto a laser cutter; 2) DungeonMaker assesses player-crafted artifacts; 3) DungeonMaker's modified laser head senses and moves player- and non-player figures, and 4) can physically damage figures. An evaluation (n=4x3) indicated that DungeonMaker provides an engaging experience, may support players' connection to their figures, and potentially spark novices' interest in fabrication. DungeonMaker provides a rich constellation to play HBGs by blending aspects of craft and automation to couple the physical and digital elements of an HBG tightly.
ABSTRACT - Legal frameworks rely on users to make an informed decision about data collection, e.g., by accepting or declining the use of tracking technologies. In practice, however, users hardly interact with tracking consent notices on a deliberate website per website level, but usually accept or decline optional tracking technologies altogether in a habituated behavior. We explored the potential of three different nudge types (color highlighting, social cue, timer) and default settings to interrupt this auto-response in an experimental between-subject design with 167 participants. We did not find statistically significant differences regarding the buttons clicked. Our results showed that opt-in default settings significantly decrease tracking technology use acceptance rates. These results are a first step towards understanding the effects of different nudging concepts on users’ interaction with tracking consent notices.
ABSTRACT - Personalized privacy assistants (PPAs) communicate privacy-related decisions of their users to Internet of Things (IoT) devices. There are different ways to implement PPAs by varying the degree of autonomy or decision model. This paper investigates user perceptions of PPA autonomy models and privacy profiles -- archetypes of individual privacy needs -- as a basis for PPA decisions in private environments (e.g., a friend's home). We first explore how privacy profiles can be assigned to users and propose an assignment method. Next, we investigate user perceptions in 18 usage scenarios with varying contexts, data types and number of decisions in a study with 1126 participants. We found considerable differences between the profiles in settings with few decisions. If the number of decisions gets high ($>$ 1/h), participants exclusively preferred fully autonomous PPAs. Finally, we discuss implications and recommendations for designing scalable PPAs that serve as privacy interfaces for future IoT devices.
ABSTRACT - Electrodermal activity (EDA) reflects changes in skin conductance, closely tied to human psychological states. EDA sensors can assess stress, cognitive workload, arousal, and activity related to the parasympathetic nervous system used in various human-computer interaction applications. Yet, current limitations involve the complex attachment and proper skin contact with EDA sensors. This paper explores the concept of 3D printing electrodes for EDA measurements, potentially integrating sensors into arbitrary 3D printed objects, alleviating the need for complex assembly and attachment. We examine the adaptation of conventional EDA circuits for 3D-printed electrodes, assessing different electrode shapes and their impact on the sensing accuracy. A user study (N=6) revealed that 3D-printed electrodes can measure EDA with similar accuracy while recommending larger contact areas for improved precision. We discuss design implications to facilitate EDA sensor integration into 3D-printed devices, fostering a diverse integration into everyday items using consumer-grade 3D printers for physiological interface prototyping.
ABSTRACT - Whole-body movements enhance the presence and enjoyment of Virtual Reality (VR) experiences. However, using large gestures is often uncomfortable and impossible in confined spaces (e.g., public transport). We introduce FingerMapper, mapping small-scale finger motions onto virtual arms and hands to enable whole-body virtual movements in VR. In a first target selection study (n=13) comparing FingerMapper to hand tracking and ray-casting, we found that FingerMapper can significantly reduce physical motions and fatigue while having a similar degree of precision. In a consecutive study (n=13), we compared FingerMapper to hand tracking inside a confined space (the front passenger seat of a car). The results showed participants had significantly higher perceived safety and fewer collisions with FingerMapper while preserving a similar degree of presence and enjoyment as hand tracking. Finally, we present three example applications demonstrating how FingerMapper could be applied for locomotion and interaction for VR in confined spaces.
ABSTRACT - Mid-air gestures, widely used in today's Augmented Reality applications, are prone to the "gorilla arm" effect, leading to discomfort with prolonged interactions. While prior work has proposed metrics to quantify this effect and means to improve comfort and ergonomics, these works usually only consider simplistic, one-dimensional AR interactions, like reaching for a point or pushing a button. However, interacting with AR environments also involves far more complex tasks, such as rotational knobs, potentially impacting ergonomics. This paper advances the understanding of the ergonomics of rotational mid-air interactions in AR. For this, we contribute the results of a controlled experiment exposing the participants to a rotational task in the interaction space defined by their arms' reach. Based on the results, we discuss how novel future mid-air gesture modalities benefit from our findings concerning ergonomic-aware rotational interaction.
ABSTRACT - Modern smartphones support FIDO2 passwordless authentication using either external security keys or internal biometric authentication, but it is unclear whether users appreciate and accept these new forms of web authentication for their own accounts. We present the first lab study (N=87) comparing platform and roaming authentication on smartphones, determining the practical strengths and weaknesses of FIDO2 as perceived by users in a mobile scenario. Most participants were willing to adopt passwordless authentication during our in-person user study, but closer analysis shows that participants prioritize usability, security, and availability differently depending on the account type. We identify remaining adoption barriers that prevent FIDO2 from succeeding password authentication, such as missing support for contemporary usage patterns, including account delegation and usage on multiple clients.
ABSTRACT - Human memory has notable limitations (e.g., forgetting) which have necessitated a variety of memory aids (e.g., calendars). As we grow closer to mass adoption of everyday Extended Reality (XR), which is frequently leveraging perceptual limitations (e.g., redirected walking), it becomes pertinent to consider how XR could leverage memory limitations (forgetting, distorting, persistence) to induce memory manipulations. As memories highly impact our self-perception, social interactions, and behaviors, there is a pressing need to understand XR Memory Manipulations (XRMMs). We ran three speculative design workshops (n=12), with XR and memory researchers creating 48 XRMM scenarios. Through thematic analysis, we define XRMMs, present a framework of their core components and reveal three classes (at encoding, pre-retrieval, at retrieval). Each class differs in terms of technology (AR/VR) and impact on memory (influencing quality of memories, inducing forgetting, distorting memories). We raise ethical concerns and discuss opportunities of perceptual and memory manipulations in XR.
ABSTRACT - Sketching in virtual 3D environments has enabled new forms of artistic expression and a variety of novel design use-cases. However, the lack of haptic feedback proves to be one of the main challenges in this field. While prior work has investigated vibrotactile and force-feedback devices, this paper proposes the addition of thermal feedback. We present ThermalPen, a novel pen for 3D sketching that associates the texture and colour of strokes with different thermal properties. For example, a fire texture elicits an increase in temperature, while an ice texture causes a temperature drop in the pen. Our goal with ThermalPen is to enhance the 3D sketching experience and allow users to use this tool to increase their creativity while sketching. We plan on evaluating the influence of thermal feedback on the 3D sketching experience, with a focus on user creativity in the future.
ABSTRACT - From carrying grocery bags to holding onto handles on the bus, there are a variety of situations where one or both hands are busy, hindering the vision of ubiquitous interaction with technology. Voice commands, as a popular hands-free alternative, struggle with ambient noise and privacy issues. As an alternative approach, research explored movements of various body parts (e.g., head, arms) as input modalities, with foot-based techniques proving particularly suitable for hands-free interaction. Whereas previous research only considered the movement of the foot as a whole, in this work, we argue that our toes offer further degrees of freedom that can be leveraged for interaction. To explore the viability of toe-based interaction, we contribute the results of a controlled experiment with 18 participants assessing the impact of five factors on the accuracy, efficiency and user experience of such interfaces. Based on the findings, we provide design recommendations for future toe-based interfaces.
ABSTRACT - When we get lost in Virtual Reality (VR) or want to return to a previous location, we use the same methods of locomotion for the way back as for the way forward. This is time-consuming and requires additional physical orientation changes, increasing the risk of getting tangled in the headsets' cables. In this paper, we propose the use of undo actions to revert locomotion steps in VR. We explore eight different variations of undo actions as extensions of point&teleport, based on the possibility to undo position and orientation changes together with two different visualizations of the undo step (discrete and continuous). We contribute the results of a controlled experiment with 24 participants investigating the efficiency and orientation of the undo techniques in a radial maze task. We found that the combination of position and orientation undo together with a discrete visualization resulted in the highest efficiency without increasing orientation errors.
ABSTRACT - Two-factor authentication (2FA) is a recommended or imposed authentication mechanism for valuable online assets. However, 2FA mechanisms usually exhibit user experience issues that create user friction and even lead to poor acceptance, hampering the wider spread of 2FA. In this article, we investigate user perceptions of 2FA through in-depth interviews with 42 participants, revealing key requirements that are not well met today despite recently emerged 2FA solutions. First, we investigate past experiences with authentication mechanisms emphasizing problems and aspects that hamper good user experience. Second, we investigate the different authentication factors more closely. Our results reveal particularly interesting preferences regarding the authentication factor “ownership” in terms of properties, physical realizations, and interaction. These findings suggest a path toward 2FA mechanisms with considerably better user experience, promising to improve the acceptance and hence, the proliferation of 2FA for the benefit of security in the digital world.
ABSTRACT - Creating highly realistic Virtual Reality (VR) bicycle experiences can be time-consuming and expensive. Moreover, it is unclear what hardware parts are necessary to design a bicycle simulator and whether a bicycle is needed at all. In this paper, we investigated cycling fidelity and control of VR bicycle simulators. For this, we developed and evaluated three cycling simulators: (1) cycling without a bicycle (bikeless), (2) cycling on a fixed (stationary) and (3) moving bicycle (tandem) with four levels of control (no control, steering, pedaling, and steering + pedaling). To evaluate all combinations of fidelity and control, we conducted a controlled experiment (N = 24) in indoor and outdoor settings. We found that the bikeless setup provides the highest feeling of safety, while the tandem leads to the highest realism without increasing motion sickness. Moreover, we discovered that bicycles are not essential for cycling in VR.
ABSTRACT - Perceptual manipulations (PMs) in Virtual Reality (VR) can steer users’ actions (e.g., redirection techniques) and amplify haptic perceptions (e.g., weight). However, their ability to amplify or induce negative perceptions such as physical pain is not well understood. In this work, we explore if PMs can be leveraged to induce the perception of pain, without modifying the physical stimulus. We implemented a VR experience combined with a haptic prototype, simulating the dislocation of a finger. A user study (n=18) compared three conditions (visual-only, haptic-only and combined) on the perception of physical pain and physical discomfort. We observed that using PMs with a haptic device resulted in a significantly higher perception of physical discomfort and an increase in the perception of pain compared to the unmodified sensation (haptic-only). Finally, we discuss how perception of pain can be leveraged in future VR applications and reflect on ethical concerns.
ABSTRACT - Cycling is emerging as a relevant alternative to cars. However, the more people commute by bicycle, the higher the number of cyclists who use their smartphones on the go and endanger road safety. To better understand input while cycling, in this paper, we present the design and evaluation of three text input methods for cyclists: (1) touch input using smartphones, (2) midair input using a Microsoft Hololens 2, and (3) a set of ten physical buttons placed on both sides of the handlebar. We conducted a controlled indoor experiment (N = 12) on a bicycle simulator to evaluate these input methods. We found that text input via touch input was faster and less mentally demanding than input with midair gestures and physical buttons. However, the midair gestures were the least error-prone, and the physical buttons facilitated keeping both hands on the handlebars and were more intuitive and less distracting.
