Kasper Hornbæk

University of Copenhagen · Department of Computer Science

In virtual reality (VR), interactions may fail when users encounter new, unknown, or unexpected objects. We propose using feedforward in VR to help users interact with objects by revealing how such objects work. Feedforward lets users know what to do and how to do it by showing the available actions and outcomes before an interaction. In this paper...

Body ownership illusions (BOIs) occur when participants experience that their actual body is replaced by a body shown in virtual reality (VR). Based on a systematic review of the cumulative evidence on BOIs from 111 research papers published in 2010 to 2021, this article summarizes the findings of empirical studies of BOIs. Following the PRISMA gui...

One of the most fundamental interactions –pointing– is well understood on flat surfaces. However, pointing performance on tangible surfaces with physical targets is still limited for Tangible User Interfaces (TUIs). We investigate the effect of a target’s physical width, height, and distance on user pointing performance. We conducted a study using...

Transfer functions with a high translational gain can increase the range of walking in virtual reality. These functions determine how much virtual movements are amplified compared to the corresponding physical movements. However, it is unclear how the design of these functions influences the user’s gait and experience when walking with high gain va...

Mid-air haptic stimulation can enrich user experience during human-computer interaction. However, the design space of such stimuli is large due to the number and range of stimulation parameters. It therefore remains difficult for designers to select a stimulus to induce an intended experience. We derive a mapping for mid-air experiences based on tw...

Sense of control is increasingly used as a measure of quality in human-computer interaction. Control has been investigated mainly at a high level, using subjective questionnaire data, but also at a low level, using objective data on participants’ sense of agency. However, it remains unclear how differences in higher level, experienced control refle...

Human-computer integration is an emerging area in which the boundary between humans and technology is blurred as users and computers work collaboratively and share agency to execute tasks. The sense of agency (SoA) is an experience that arises by a combination of a voluntary motor action and sensory evidence whether the corresponding body movements...

The time we each spend using smartphones is increasing. So is the extent of discussions on whether that time is well spent and whether it results in positive experiences and ultimately improves well-being. However, research on this question rarely links the time spent on smartphones, the specific applications used, the motivation for using them and...

This essay addresses a foundational topic in applied sciences with interest in design: how do theories inform design? Previous work has attributed theory-use to abduction and deduction. However, design is about creating an intervention, a possible state that does not exist presently, and these accounts fail to explain how theories permit taking thi...

A key challenge HCI researchers face when designing a controlled experiment is choosing the appropriate number of participants, or sample size. A priori power analysis examines the relationships among multiple parameters, including the complexity associated with human participants, e.g., order and fatigue effects, to calculate the statistical power...

A key challenge HCI researchers face when designing a controlled experiment is choosing the appropriate number of participants, or sample size. A prior power analysis examines the relationships among multiple parameters, including the complexity associated with human participants, e.g., order and fatigue effects, to calculate the statistical power...

The human sense of smell is powerful. However, the way we use smell as an interaction modality in human–computer interaction (HCI) is limited. We lack a common reference point to guide designers’ choices when using smell. Here, we map out an olfactory design space to provide designers with such guidance. We identified four key design features: (i)...

Human bodies influence the owners' affect through posture, facial expressions, and movement. It remains unclear whether similar links between virtual bodies and affect exist. Such links could present design opportunities for virtual environments and advance our understanding of fundamental concepts of embodied VR. An initial outside-the-lab between...

The skin offers exciting possibilities for human--computer interaction by enabling new types of input and feedback. We survey 42 research papers on interfaces that allow users to give input on their skin. Skin-based interfaces have developed rapidly over the past 8 years but most work consists of individual prototypes, with limited overview of poss...

The notion of interaction is essential to human-computer interaction, yet rarely studied. We use quantitative and qualitative methods to investigate how this notion has been used across 35 years of proceedings from the ACM Conference on Human Factors in Computing (CHI). Using natural language processing, we extract 53,568 occurrences of the word “i...

The view of quality in human-computer interaction continuously develops, having in past decades included consistency, transparency, usability, and positive emotions. Recently, meaning is receiving increased interest in the user experience literature and in industry, referring to the end, purpose or significance of interaction with computers. Howeve...

" We rely on our sight when manipulating objects. When objects are occluded, manipulation becomes difficult. Such occluded objects can be shown via augmented reality to re-enable visual guidance. However, it is unclear how to do so to best support object manipulation. We compare four views of occluded objects and their effect on performance and sat...

Wall displays support people in interacting with large information spaces in two ways: On the one hand, the physical space in front of such displays enables them to navigate information spaces physically. On the other hand, the visual overview of the information space on the display may promote the formation of spatial memory; from studies of deskt...

Around-device interaction methods expand the available interaction space for mobile devices; however, there is currently no way to simultaneously track a user's input and provide haptic feedback at the tracked point away from the device. We present Magnetips, a simple, mobile solution for around-device tracking and mid-air haptic feedback. Magnetip...

Tool use extends people's representations of the immediately actionable space around them. Physical tools thereby become integrated in people's body schemas. We introduce a measure for tool extension in HCI by using a visual-tactile interference paradigm. In this paradigm, an index of tool extension is given by response time differences between cro...

Human-computer interaction is replete with ways of talking about qualities of interaction or interfaces, including if they are expressive, rich, fluid, or playful. An example of such a quality is subtle. While this word is frequently used in the literature, we lack a coherent account of what it means to be subtle, how to achieve subtleness in an in...

This paper provides resources and design recommendations for optimizing position input for pressure sensor matrices, a sensor design often used in eTextiles. Currently applications using pressure matrices for precise continuous position control are rare. One reason designers opt against using these sensors for continuous position control is that wh...

Grabbing users' attention is a fundamental aspect of interactive systems. However, there is a disconnect between the ways our devices notify us and how our bodies do so naturally. In this paper, we explore the body's modality of itching as a way to provide such natural feedback. We create itching sensations via low-current electric stimulation, whi...

Electrical Muscle Stimulation (EMS) offers rich opportunities for interaction. By varying stimulation parameters (amplitudes, pulse widths and frequencies), EMS can be used to either trigger muscle contractions, and so convey object affordances or guide user movements, or provide rich haptic feedback. However, the way users' experience changes with...

Many shape-changing interfaces use an array of actuated rods to create a display surface; each rod working as a pixel. However, this approach only supports pixel height manipulation and cannot produce more radical shape changes of each pixel (and thus of the display). Examples of such changes include non-horizontal pixels, pixels that overhang othe...

Input on the skin is emerging as an interaction style. At CHI 2012, Coyle and colleagues identified an increase in the sense of agency (SoA) as one benefit of skin input. However, their study only compared skin input to button presses and has not, to our knowledge, been replicated. Therefore, we had 24 participants compare skin input to both button...

The Sense of Agency (SoA) refers to our capability to control our own actions and influence the world around us. Recent research in HCI has been investigating SoA to provide users an instinctive sense of "I did that" as opposed to "the system did that". However, current agency measurements are limited. The Intentional Binding (IB) paradigm provides...

The concept of power pose originates from a Psychology study from 2010 which suggested that holding an expansive pose can change hormone levels and increase risk-taking behavior. Follow-up experiments suggested that expansive poses incidentally imposed by the design of an environment lead to more dishonest behaviors. While multiple replication atte...

Advances in sensing technologies allow for using the forearm as a touch surface to give input to off-skin displays. However, it is unclear how users perceive the mapping between an on-skin input area and an off-skin display area. We empirically describe such mappings to improve on-skin interaction. We collected discrete and continuous touch data in...

Research on virtual reality (VR) has studied users' experience of immersion, presence, simulator sickness, and learning effects. However, the momentary experience of exiting VR and transitioning back to the real-world is not well understood. Do users become self-conscious of their actions upon exit? Are users nervous of their surroundings? Using ex...

Can we experience haptic textures in mid-air? Typically, the experience of texture is caused by vibration of the fingertip as it moves over the surface of an object. This object's surface also guides the finger's movement, creating an implicit motion-to-vibration mapping. If we wish to simulate a texture in mid-air, such guidance does not exist, ma...

Shape-changing interfaces have emerged as a new method for interacting with computers, using dynamic changes in a device's physical shape for input and output. With the advances of research into shape-changing interfaces, we see a need to synthesize the main, open research questions. The purpose of this synthesis is to formulate common challenges a...

We introduce the concept of Veritaps: a communication layer to help users identify truths and lies in mobile input. Existing lie detection research typically uses features not suitable for the breadth of mobile interaction. We explore the feasibility of detecting lies across all mobile touch interaction using sensor data from commodity smartphones....

We present zPatch: an eTextile patch for hover, touch, and pressure input, using both resistive and capacitive sensing. zPatches are made by layering a piezo-resistive material between silver-plated ripstop, and embedding it in non-conductive fabric to form a patch. zPatches can be easily ironed onto most fabrics, in any location, enabling easy pro...

Electric Muscle Stimulation (EMS) has emerged as an interaction paradigm for HCI. It has been used to confer object affordance, provide walking directions, and assist with sketching. However, the electrical signals used for EMS are multi-dimensional and require expert calibration before use. To date, this calibration has occurred as a collaboration...

Many user studies are now conducted outside laboratories to increase the number and heterogeneity of participants. These studies are conducted in diverse settings, with the potential to give research greater external validity and statistical power at a lower cost. The feasibility of conducting virtual reality (VR) studies outside laboratories remai...

Usability has a distinct subjective component, yet surprisingly little is known about its neural basis and relation to the neuroanatomy of aesthetics. To begin closing this gap, we conducted two functional magnetic resonance imaging studies in which participants were shown static webpages (in the first study) and videos of interaction with webpages...

Understanding the mechanisms that shape the adoption and use of information technology is central to human--computer interaction. Two accounts are particularly vocal about these mechanisms, namely the technology acceptance model (TAM) and work on user experience (UX) models. In this study, we review 37 papers in the overlap between TAM and UX model...

Electric muscle stimulation (EMS) can enable mobile force feedback, support pedestrian navigation, or confer object affordances. To date, however, EMS is limited by two interlinked problems. (1) EMS is low resolution -- achieving only coarse movements and constraining opportunities for exploration. (2) EMS requires time consuming, expert calibratio...

The term interaction is field-defining, yet surprisingly confused. This essay discusses what interaction is. We first argue that only few attempts to directly define interaction exist. Nevertheless, we extract from the literature distinct and highly developed concepts, for instance viewing interaction as dialogue, transmission, optimal behavior, em...

The human skin provides an ample, always-on surface for input to smart watches, mobile phones, and remote displays. Using touch on bare skin to issue commands, however, requires users to recall the location of items without direct visual feedback. We present an in-depth study in which participants placed 30 items on the hand and forearm and attempt...

Vibrotactile actuation is mainly used to deliver buzzing sensations. But if vibrotactile actuation is tightly coupled to users' actions, it can be used to create much richer haptic experiences. It is not well understood, however, how this coupling should be done or which vibrotactile parameters create which experiences. To investigate how actuation...

Recent research suggests that psychological needs such as competence and relatedness are involved in users' experience with technology and are related to the perception of a product's hedonic and pragmatic quality. This line of research, however, predominately focuses on positive leisure experiences, and it is unclear whether need fulfillment plays...

Current techniques to computationally detect human affect often depend on specialized hardware, work only in laboratory settings, or require substantial individual training. We use sensors in commodity smartphones to estimate affect in the wild with no training time based on a link between affect and movement. The first experiment had 55 participan...

Physical data representations, or data physicalizations, are a promising new medium to represent and communicate data. Previous work mostly studied passive physicalizations which require humans to perform all interactions manually. Dynamic shape-changing displays address this limitation and facilitate data exploration tasks such as sorting, navigat...

An instructional approach is presented to improve human performance in solving Bayesian inference problems. Starting from the original text of the classic Mammography Problem, the textual expression is modified and visualizations are added according to Mayer's principles of instruction. These principles concern coherence, personalization, signaling...

The design of shape-changing interfaces to show emotions relies on craft skill with few clear guidelines. Through two experiments, we explore how to design such interfaces using theories of the relation between biological motion and affect. In the first experiment, 19 participants viewed six shape-changing behaviors that varied the velocity, fluidi...

We present TableHop, a tabletop display that provides controlled self-actuated deformation and vibro-tactile feedback to an elastic fabric surface while retaining the ability for high-resolution visual projection. The surface is made of a highly stretchable pure spandex fabric that is electrostatically actuated using electrodes mounted on its top o...

The size of information spaces often exceeds the limits of even the largest displays. This makes navigating such spaces through on-screen interactions demanding. However, if users imagine the information space extending in a plane beyond the display's boundaries, they might be able to use the space beyond the display for input. This paper investiga...

This essay contributes a meta-scientific account of human-computer interaction (HCI) research as problem-solving. We build on the philosophy of Larry Laudan, who develops problem and solution as the foundational concepts of science. We argue that most HCI research is about three main types of problem: empirical, conceptual, and constructive. We ela...

Wall-sized displays support group work by allowing several people to work both separately and together. However, whether people interact directly through touch input or indirectly through mouse input can have profound effects on collaboration. We present a study that compares how groups collaborate using either multitouch or multiple mice on a wall...

Shape-changing interfaces allow designers to create user interfaces that physically change shape. However, presently, we lack studies of how such interfaces are designed, as well as what high-level strategies, such as metaphors and affordances, designers use. This paper presents an analysis of sketches made by 21 participants designing either a sha...

Research on shape-changing interfaces has explored various technologies, parameters for shape changes, and transformations between shapes. While much is known about how to implement these variations, it is unclear what affordance they provide, how users understand their relation to the underlying system state, and how feedback via shape change is p...

The use of the skin as interaction surface is gaining popularity in the HCI community. To offer an alternative perspective on how we might design on-body interactions, we conducted a questionnaire asking if, how, and why people mark their skin. We found that visibility and ease of access were important factors for choosing to mark the body. We also...

Peer-review is key to assessing work in HCI conferences. The content and process of peer-review, and how it moves scholarship forward or impedes it, are much discussed but little data is available. We provide initial data from surveying 46 authors who submitted papers and notes to CHI 2016, and asking them what they found helpful and unhelpful in t...

User experience (UX) research has expanded our notion of what makes interactive technology good, often putting hedonic aspects of use such as fun, affect, and stimulation at the center. Outside of UX, the hedonic is often contrasted to the eudaimonic, the notion of striving towards one's personal best. It remains unclear, however, what this distinc...

" While current mobile devices detect the presence of surrounding devices, they lack a truly spatial awareness to bring them into the user's natural 3D space. We present Tracko, a 3D tracking system between two or more commodity devices without added components or device synchronization. Tracko achieves this by fusing three signal types. 1) Tracko...

Users can interact with large displays in many ways, including touch and mid-air gestures. However, it remains unclear how these ways compare and when users choose one over the other. In a first experiment, we compare touch and mid-air gestures to identify their relative performance for target acquisition. In a second experiment, participants choos...

Parallel Coordinate Plots (PCPs) is one of the most powerful techniques for the visualization of multivariate data. However, for large datasets, the representation suffers from clutter due to overplotting. In this case, discerning the underlying data information and selecting specific interesting patterns can become difficult. We propose a new and...

This article investigates Herzberg's [1959] notion of hygienes, factors contributing to dissatisfaction but not to satisfaction, and motivators, factors contributing to satisfaction but not to dissatisfaction, in the context of user experience (UX). Earlier work has theorized that the notion of hygienes and motivators applies to UX but has neither...

Before using an interactive product, people form expectations about what the experience of use will be like. These expectations may affect both the use of the product and users’ attitudes toward it. This article briefly reviews existing theories of expectations to design and perform two crowdsourced experiments that investigate how expectations aff...

Trying to make a decision between two outcomes, when there is some level of uncertainty, is inherently difficult because it involves probabilistic reasoning. Previous studies have shown that most people do not correctly apply Bayesian inference to solve probabilistic problems for decision making under uncertainty. In an effort to improve decision m...

Physical movement plays an important role in interaction with wall-displays. Earlier work on its effect on performance has been inconclusive, however, because movement has not been experimentally controlled. In a first experiment, we controlled participants’ ability to physically move in front of a 3-meter wide 24-megapixel wall-display. Participan...

Visualizations such as bar charts help users reason about data, but are mostly screen-based, rarely physical, and almost never physical and dynamic. This paper investigates the role of physically dynamic bar charts and evaluates new interactions for exploring and working with datasets rendered in dynamic physical form. To facilitate our exploration...