Peter J Werkhoven

Utrecht University | UU · Department of Information and Computing Sciences

In teleoperations, robots are generally used because related tasks are too dangerous, uncomfortable or impossible for humans to perform. When using augmented reality to control robotic limbs in such teleoperations, it is essential to understand how these extra virtual limbs are experienced. In particular, the relationship between the embodiment exp...

The complex socio-technological debate underlying safety-critical and ethically relevant issues pertaining to AI development and deployment extends across heterogeneous research subfields and involves in part conflicting positions. In this context, it seems expedient to generate a minimalistic joint transdisciplinary basis disambiguating the refere...

The classic rubber hand illusion (RHI) experiment studies the sense of embodiment over a fake limb. Distinguished subcomponents of embodiment are ownership (sense of self-attribution of a body), agency (sense of having motor control), and self-location (the spatial experience of being inside a body), and are typically evoked in either reality or vi...

In recent years, the implementation of meaningfully controllable advanced intelligent systems whose goals are aligned with ethical values as specified by human entities emerged as key subject of investigation of international relevance across diverse AI-related research areas. In this paper, we present a novel transdisciplinary and Systems Engineer...

Recent progress in Artificial Intelligence, sensing and network technology, robotics, and (cloud) computing has enabled the development of intelligent autonomous machine systems. Telling such autonomous systems "what to do" in a responsible way, is a non-trivial task. For intelligent autonomous machines to function in human society and collaborate...

The majority of augmented reality (AR) research has been concerned with visual perception, however the move towards multimodality is imminent. At the same time, there is no clear vision of what multimodal AR is. The purpose of this position paper is to consider possible ways of examining AR other than using popular notions and definitions, in order...

Augmented reality applications using stereo head-mounted displays are not capable of perfectly blending real and virtual objects. For example, depth in the real world is perceived through cues such as accommodation and vergence. However, in stereo head-mounted displays these cues are disconnected since the virtual is generally projected at a static...

Haptic feedback, such as the sensation of 'being touched', is an essential part of how we experience our environment. Yet, it is often disregarded in current virtual reality (VR) systems. In addition to the technical challenge of creating such tactile experiences there are also human aspects that are not fully understood, especially with respect to...

Digital games have been used as stressors in a range of disciplines for decades. Nonetheless, the underlying characteristics of these stressors and the study in which the stressor was applied are generally not recognized for their moderating effect on the measured physiological stress responses. We have therefore conducted a meta-analysis that ana...

In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no a...

Gaze-independent event-related potential (ERP) based brain-computer interfaces (BCIs) yield relatively low BCI performance and traditionally employ unimodal stimuli. Bimodal ERP-BCIs may increase BCI performance due to multisensory integration or summation in the brain. An additional advantage of bimodal BCIs may be that the user can choose which m...

Researchers have reported that audiovisual object presentation improves memory encoding of object identity in comparison to either auditory or visual object presentation. However, multisensory memory effects on retrieval, on object location, and of other multisensory combinations are yet unknown. We investigated the effects of visuotactile presenta...

It has been shown that multisensory presentation can improve perception, attention, and object memory compared with unisensory presentation. Consequently, we expect that multisensory presentation of landmarks can improve spatial memory and navigation. In this study we tested the effect of visual, auditory and combined landmark presentations in virt...

Pairing two brief auditory beeps with a single flash can evoke the percept of a second, illusory, flash. Investigations of the underlying neural mechanisms are limited to post-stimulus effects of this sound-induced illusory flash. We investigated whether touch modulates the visual evoked potential in a similar vein, and also looked at pre-stimulus...

The brain is able to determine angular self-motion from visual, vestibular, and kinesthetic information. There is compelling evidence that both humans and non-human primates integrate visual and inertial (i.e., vestibular and kinesthetic) information in a statistically optimal fashion when discriminating heading direction. In the present study, we...

When using Brain Computer Interfaces (BCIs) to control a game, the BCI may have to compete with gaming tasks for the same perceptual and cognitive resources. We investigated (1) if and to what extent event related potentials (ERPs) and ERP-BCI performance are affected in a dual-task situation, and (2) if these effects are a function of the level of...

This chapter discusses mechanisms of multimodal perception in the context of multimodal simulators and virtual worlds. We review some notable findings from psychophysical experiments with a focus on what we call “touch inclusive multimodal perception,” that is, the sensory integration of the tactile system with other sensory systems such as vision...

In the illusory flash paradigm, a single flash may be experienced as two flashes when accompanied by two beeps or taps, and two flashes may be experienced as a single flash when accompanied by one beep or tap. The classic paradigm restricts responses to '1' and '2' (2-AFC), ignoring possible qualitative differences between real and illusory flashes...

Although the mechanisms of neural adaptation to weightlessness and re-adaptation to Earth-gravity have received a lot of attention since the first human space flight, there is as yet little knowledge about how spatial orientation is affected by partial gravity, such as lunar gravity of 0.16 g or Martian gravity of 0.38 g. Up to now twelve astronaut...

Event-related potential (ERP)-based brain-computer interfaces (BCIs) employ differences in brain responses to attended and ignored stimuli. Typically, visual stimuli are used. Tactile stimuli have recently been suggested as a gaze-independent alternative. Bimodal stimuli could evoke additional brain activity due to multisensory integration which ma...

The development of Brain Computer Interfaces (BCIs) enters a phase in which these devices are no longer restricted to applications in controlled, single-task environments. For instance, BCIs for gaming or high-end operator stations will function as part of a multimodal user interface in a multitask environment. This phase introduces new issues that...

Unlabelled: Event-related potential (ERP) based brain-computer interfaces (BCIs) employ differences in brain responses to attended and ignored stimuli. When using a tactile ERP-BCI for navigation, mapping is required between navigation directions on a visual display and unambiguously corresponding tactile stimuli (tactors) from a tactile control d...

In Illusory Flash (IF) experiments, congruent multisensory presentation has no effect on the mean estimate of the number of events, but decreases the variance in comparison with unisensory presentation. In contrast, congruent multisensory presentation in other Temporal Numerosity Judgement (TNJ) tasks affects the mean estimate (i.e., it often resul...

The development of Brain Computer Interfaces (BCIs) enters a phase in which these devices are no longer restricted to applications in controlled, single-task environments. For instance, BCIs for gaming or high-end operator stations will function as part of a multimodal user interface in a multitask environment. This phase introduces new issues that...

This study investigated how human locomotion through an obstacle environment is influenced by visual field limitation. Participants were asked to walk at a comfortable pace to a target location while avoiding multiple vertical objects. During this task, they wore goggles restricting their visual field to small (S: 40°×25°), medium (M: 80°×60°), lar...

In this study, the authors investigated how restriction of the vertical viewing angle influences obstacle-crossing behavior. Twelve participants stepped over obstacles of different dimensions while wearing visual-field-restricting goggles. Using full-body motion capture, several kinematic measures were extracted and analyzed. Results indicate that...

In this chapter we discuss Brain-Computer Interfaces (BCIs) as navigation devices from a Human Factors point of view. We argue that navigation is more than only steering a car or a wheelchair. It involves three levels: planning, steering and control, linked to cognition, perception and sensation, respectively. We structure the existing BCIs along t...

This paper studies semantic efficiency measures for ambient intelligence. We follow an agent-based approach and investigate how large quantities of information can be efficiently handled. We will show how to dynamically set up a communication network between agents, which aims to minimize the communication load. The approach is based on a formal on...

In the present study, we investigated whether the perception of heading of linear self-motion can be explained by Maximum Likelihood Integration (MLI) of visual and non-visual sensory cues. MLI predicts smaller variance for multisensory judgments compared to unisensory judgments. Nine participants were exposed to visual, inertial, or visual-inertia...

Knowledge of human motion perception can be applied in the optimization of motion cueing algorithms. In the past it has been shown that some discrepancies between the amplitude or phase of a visual and inertial cue go unnoticed. These acceptable discrepancies are referred to as coherence zones. In the present experiment we investigate whether a coh...

When the presentation of a single flash is paired with that of 2 taps, a second, illusory, flash is sometimes perceived. We presented participants with 1 or 2 flashes paired with 1 or 2 taps and asked them to report the number of flashes. In experiment 1, we used the response categories 1, 2, 3 and analyzed the responses to 2 consecutive illusory f...

In this paper, we describe a Brain Computer Interface (BCI) for navigation. The system is based on detecting brain signals that are elicited by tactile stimulation on the torso indicating the desired direction.

Irrelevant events in one sensory modality can influence the number of events that are perceived in another modality. Previously, the underlying process of sensory integration was studied in conditions in which participants knew a priori which sensory modality was relevant and which was not. Consequently, (bottom-up) sensory interference and (top-do...

This paper discusses a variety of potential applications of intelligent assistants, from personal digital assistant (PDA) to team digital assistant (TDA). We identify two challenges that arise when developing intelligent assistants in crisis management and give an overview of the different technologies that could be used to address these challenges...

An experiment was conducted to examine how communication patterns and task performance differ as a function of the group's communication environment and how these processes change over time. In a longitudinal design, three-person groups had to select and argue the correct answer out of a set of three alternatives for ten questions. Compared with fa...

In temporal numerosity judgment, observers systematically underestimate the number of pulses. The strongest underestimations occur when stimuli are presented with a short interstimulus interval (ISI) and are stronger for vision than for audition and touch. We investigated if multisensory presentation leads to a reduction of underestimation. Partici...

This paper studies the use of agent communication in ubiquitous computing. This application domain allows us to investigate the efficient handling of large quantities of information in agent-based systems. We will present an approach to dynamically set up a communication network between agents which aims to minimize the communication load. The appr...

The successful application of ubiquitous computing in crisis management requires a thorough understanding of the mechanisms that extract information from sensors and communicate it via PDA’s to crisis workers. Whereas query and subscribe protocols are well studied mechanisms for information exchange between different computers, it is not straightfo...

This paper proposes a decentralized approach for modeling information flow in ambient environments.We study how query and notification mechanisms can be used to reduce the amount of information exchanged between agents. We will propose qualitative criteria which state whether querying a concept is appropriate given the logical structure of an agent...

Recent improvements in computer systems and displays have enabled new simulation technologies such as Augmented, Mixed, and Virtual Environments (AMVE). Increased computer power at low cost, wireless networks, miniaturization of sensor and computer components, and better visual, auditory and tactile display systems are contributing to the maturatio...

This paper studies the use of agent communication in ubiquitous computing. This application domain allows us to investigate the efficient handling of large quantities of information in agent-based systems. We will present an approach to dynamically set up a communication network between agents which aims to minimize the communication load. The appr...

This paper focuses on the application of intuitive game interfaces (including brain machine interfaces) to serious gaming, in particular real-time, interactive, and highly realistic environments for advanced concept development, experimentation and training.

Abstract Multisensory integration happens automatically and creates a single, coherent and unambiguosly percept about the events in the world. Sometimes integration happens when sensory channels yield information about different events. A consistant body of literature seems to suggest that for incongruent sensory channels integration takes place ba...

Handheld displays leave little space for the visualization and navigation of spatial layouts representing rich information spaces. The most common navigation method for handheld displays is static peephole navigation : The peephole is static and we move the spatial layout behind it (scrolling). A more natural method is dynamic peephole navigation:...

Access to navigation information rapidly becomes standard in many situations, for example through GPS receivers and collision avoidance systems in cars. However, perceiving and processing the information may result in overloading the user's visual sense and cognitive resources. Intuitive navigation information presentation concepts using the sense...

Brain Machine Interfaces (BMIs) enable direct communication between the brain or nervous system and a machine without involving the sensory-motor system. BMIs are an embryonic technology and remarkable accomplishments have recently been reported. BMIs have a high potential and possibly an enormous impact on society, and may evoke a revolution in th...

Handheld displays leave little space for the visualization and navigation of spatial layouts representing rich information spaces. The most common navigation method for handheld displays is static peephole navigation: The peephole is static and we move the spatial layout behind it (scrolling). A more natural method is dynamic peephole navigation: h...

Handheld displays leave little space for the visualization and navigation of spatial layouts representing rich information spaces. The most common navigation method for handheld displays is static peephole navigation: The peephole is static and we move the spatial layout behind it (scrolling). A more natural method is dynamic peephole navigation: h...

An alternative for scrolling on hand held displays is dynamic peephole navigation: scanning a spatial layout using a spatially tracked hand-held display as a moving peephole. We found that dynamic peephole navigation allows users to discriminate geometric features of the spatial layout roughly 50% more accurately and 25% faster than with scrolling....

Fundamental to human existence is the ability to capture, memorize and retrieve personal experiences and to share them with others. Can systems help us to capture and retrieve experiences? After motors have supplemented our muscles and sensors have supplemented our senses, emerging computer systems are on the verge of becoming intimate supplements...

We investigated the consistency between tactually and visually designated empty time intervals. In a forced-choice discrimination task, participants judged whether the second of two intervals was shorter or longer than the first interval. Two pulses defined the intervals. The pulse was either a vibro-tactile burst presented to the fingertip, or a f...

The type of navigation interface in a virtual environment (VE)--head slaved or indirect--determines whether or not proprioceptive feedback stimuli are present during movement. In addition, teleports can be used, which do not provide continuous movement but, rather, discontinuously displace the viewpoint over large distances. A two-part experiment w...

The visual component of conversational media such as videoconferencing systems communicates important non-verbal information such as facial expressions, gestures, posture and gaze. Unlike the other cues, selective gaze depends critically on the configuration of cameras and monitors. Under isotropic videoconferencing conditions people see each other...

Spatial orientation in a Virtual Environment (VE) depends on visual recognition and on path integration meaning that the traversed path is integrated from feedback stimuli (visual, vestibular, and kinesthetic). Which stimuli are available, depends on whether an immersive interface is used with head-slaved movement or a non-immersive interface is us...

When moving around in the world, humans can use the motion sensations provided by their kinesthetic, vestibular, and visual senses to maintain their sense of direction. Previous research in virtual environments (VEs) has shown that this so-called path integration process is inaccurate in the case that only visual motion stimuli are present, which m...

Immersive simulation techniques such as Virtual Environments (VE) can revolutionize human factors engineering and training projects provided that they are carefully validated. Is human performance in the virtual world the same as in the real world? When visual aspects perceived on a virtual ship differ from those perceived on a real ship, human fac...

To effectively use a virtual environment (VE) for applications such as training and design evaluation, a good sense of orientation is needed in the VE. “Natural” human geographical orientation, when moving around in the world, relies on visual as well as proprioceptive feedback. However, the present navigation metaphors that are used to move around...

In virtual environments the virtual hand may not always be exactly aligned with the real hand. Such misalignment may cause an adaptation of the users’ eye-hand coordination. Further, misalignment may cause a decrease in manipulation performance compared to aligned conditions. This experimental study uses a prism-adaptation paradigm to explore visuo...

We have studied manipulation performance in virtual environments using two types of controlers: virtual hand control and 3D mouse/cursors control. These manipulation methods were tested under monoscopic and stereoscopic viewing conditions. Participants were asked to discriminate, grasp, pitch, roll and position virtual objects. Both speed and accur...

In most applications of virtual environments (VEs), like training and design evaluation, a good sense of orientation is needed in the VE. Orientation performance when moving around in the real world relies on visual as well as proprioceptive feedback. However, the navigation metaphors which are used to move around the VE often lack proprioceptive f...

Virtual hand control is a direct natural manipulation method in virtual environments enabling advanced applications in the field of interactive design, training, medicine, etc. This experimental study uses a prism adaptation paradigm to explore visuo-motor adaptation to misaligned virtual hand position.

Immersive simulation techniques such as Virtual Environments (VE) can revolutionize training projects provided that they allow high-level natural interaction with the environment. TNO HFRI has carried out a research program focussed on high-level direct manipulation methods (virtual hand control). Direct manipulation allows users to grasp, rotate...

Virtual Environment (VE) techniques were developed and applied for studying different bridge concepts for a new frigate of the Royal Netherlands Navy. Firstly, thorough function-analysis and task-allocation studies were carried out. Secondly, officers of the Royal Netherlands Navy could virtually see and walk through the bridge and bridge wings of...

By order of the Royal Netherlands Air Force, TNO Human Factors Research Institute has carried out a study on how to infer from anthropometric data available the expected longitudinal changes in body measures of present day high-school graduates. Longitudinal growth is determined by repeatedly measuring the body measures of the same subjects over a...

The TNO Human Factors Institute is increasingly using virtual reality (VR) tools to create virtual environments for designing and building ships. The use of these tools enable naval engineers to make use of the advantages of virtual prototyping and concurrent engineering to develop ergonomically designed marine vessels. VR tools also help them impr...

As a three-dimensional object is moving through our world, we generally obtain a vivid impression of both its structure and its motion through space. The time-course of two-dimensional projections of the scene (optic flow) is important in conveying this three-dimensional information to us. The extent to which we can solve this specific inverse prob...

We investigated the ability of human observers to discriminate an important global 3-D structural property, namely volume, of motion-defined objects. We used convex transparent wire-frame objects consisting of about 12 planar triangular facets. Two objects, vertically separated by 7 degrees, were shown simultaneously on a computer display. Both rev...

We present an adaptive procedure to conduct psychophysical discrimination experiments. In a discrimination experiment, an observer senses (sees, hears, feels, etc.) two stimuli (separated in space or time) and is asked to order these stimuli with respect to a particular parameter (say,s). Under the usual assumption of a locally linear internal repr...

In many laboratory setups and in many day-to-day situations, a unique solution of the structure-fromtwo-views problem is unobtainable. Yet, when the visual system is presented with two projections in a sequence, it nevertheless appears to generate a reasonably stable percept of structure. In the research reported here, we examined whether the same...

We quantified the ability of human subjects to discriminate the relative distance of two points from a slanted plane when viewing the projected velocities of this scene (orthographic projection). The relative distance from a plane (called relief) is a 3-D property that is invariant under linear (affine) transformations. As such, relief can in princ...

What determines the strength of texture-defined apparent motion perception when the stimulus has no net directional energy in the Fourier domain? In a previous paper [Werkhoven, Sperling & Chubb (1993) Vision Research, 33, 463-485] we demonstrated the counterintuitive finding that the correspondence in spatial frequency and in modulation amplitude...

It has been realized for some time that the visual system performs at least two general sorts of motion processing. First-order motion processing applies some variant of standard motion analysis (i.e. spatiotemporal Fourier energy analysis) directly to stimulus luminance, whereas second-order motion processing applies standard motion analysis to on...

We examine apparent motion carried by textural properties. The texture stimuli consist of a sequence of grating patches of various spatial frequencies and amplitudes. Phases are randomized between frames to insure that first-order motion mechanisms directly applied to stimulus luminance are not systematically engaged. We use ambiguous apparent moti...

The ability of humans to visually estimate geometric angle and speed of rotation was examined as a function of the spatial scale of the stimuli. Both properties are objectively invariant at different spatial scales, but the results of experiments show that the judgement of acute geometric angles as well as that of speed of rotation varies strongly...

We present data on the human sensitivity to temporal pulse modulations of target velocity. We measured threshold detection modulation amplitudes for pulse-shaped speed modulations, as a function of pulse duration and temporal frequency. At short pulse durations (up to 50 msec) and low modulation frequency (1 Hz), detection amplitudes are ruled by B...

We present data on the human sensitivity to optic acceleration, i.e. temporal modulations of the speed and direction of moving objects. Modulation thresholds are measured as a function of modulation frequency and speed for different periodical velocity vector modulation functions using a localized target. Evidence is presented that human detection...

Energy is a phase-independent measure of stimulus strength. We show that an energy computation (that is, the energy of the spatiotemporal spectrum of some possibly nonlinear stimulus transformation) determines perceptual strength in three domains: (1) motion that is carried by luminance (first-order motion), (2) motion that is carried by textural p...

A stroboscopically presented revolving annulus composed of dots is used to elicit rotary motion perception. Observers judge the direction of rotary motion. We find sharp and gradual transitions in the probability for reversed motion perception as a function of the angle of rotation between successive frames. These transitions reveal that matches be...

Local descriptions of velocity fields (e.g., rotation, divergence, and deformation) contain a wealth of information for form perception and ego motion. In spite of this, human psychophysical performance in estimating these entities has not yet been thoroughly examined. In this paper, we report on the visual discrimination of rotary motion. A sequen...

It is tempting to explain apparent motion perception in terms of a similarity metric: the perception of apparent motion between two image elements, displayed at different positions in space and different moments in time, is carried by the similarity of the elements. Alternatively, apparent motion perception can be modeled in terms of a covariance m...

Local descriptions of velocity fields (e.g. rotation, divergence and deformation) contain a wealth of information for form-perception and ego-motion. In spite of this, human psychophysical performance in estimating these entities has not been thoroughly examined yet. In this paper, we report on the visual discrimination of rotary motion. A sequenc...

A technique that is functionally equivalent to the oriented smoothing concept and reduces numerical complexity and computational costs by eliminating the smoothness requirement from the iteration process is introduced. Local affine transformations are applied to propagate uniquely computed flow vectors into homogeneous regions and along edges in a...