When seeing an object in a scene, the presumption of seeing that object from a general viewpoint (as opposed to an accidental viewpoint) is a useful heuristic to decide which of many interpretations of this object is correct. Similar heuristic assumptions on illumination quality might also be used for scene interpretation. Here we tested that assumption and asked if illumination information helps determine object properties when seen from an accidental viewpoint. Test objects were placed on a flat surface and illumination was varied while keeping the objects' images constant. Observers judged the shape or rigidity of static or moving simple objects presented in accidental view. They also chose which of two seemingly very similar faces was familiar. We found: (1) Objects might appear flat without shadow information but were perceived to be volumetric objects or non-planar in the presence of cast shadows. (2) Apparently non-rigid objects became rigid with shadow information. (3) Shading and shadows helped to infer which of two face was the familiar one. Previous results had shown that cast shadows help determine spatial layout of objects. Our study shows that other properties of objects like rigidity or 3D-shape can be disambiguated by shadow information.

Disorientation, nausea, and vomiting of passengers that result from vehicle vibrations are characterized as kinetosis or motion sickness. It is mainly the low-frequency movements of these vehicles that contribute to the kinetosis of passengers. Frequencies that provoke kinetosis lie within the rigid-body flight characteristics of helicopters, which depend, among other things, on the design parameters of the flight control system. Moreover, the flight control system's reaction to atmospheric turbulence leads to low-frequency vibration that can result in kinetosis of the passengers and decrease the ride comfort of the helicopter. It is necessary to understand which movements of the helicopter cause kinetosis to develop countermeasures. Therefore, an extensive experimental campaign was conducted as part of a national research project. The campaign's results show that kinetosis in helicopters depends on the number of motion degrees of freedom and that the existing assessment method in ISO2631-1 is not able to reflect this correctly. Furthermore, based on the results, it can be assumed that the extent of kinetosis depends on the flight control system since the investigated flight control systems lead to different vibration spectra that expose the passengers. Therefore, consideration of kinetosis and thus ride comfort is recommended for the design procedure of future flight control systems.

Abstract Current powertrains in vehicles offer a broad spectrum of driving modes that shape the driving experience. One crucial factor for determining the human factors aspects of this driving experience is the perception and evaluation of acceleration-a complex, multisensory process that integrates auditory, vestibular, and visual input. Two important questions that need to be answered in order to better characterize this percept include: How do individual sensory inputs influence acceleration perception? and How does acceleration perception change at different acceleration levels? To address these questions, here we used a unique setup based on a cable-robot simulator that allowed us to manipulate the different modalities at different levels of acceleration with real-world, in-car data for maximum realism. Specifically, we measured the just noticeable differences (JNDs) of acceleration perception in five different modality combinations with the same set of participants. Our results showed that auditory acceleration perception was less sensitive compared to other modality combinations. In addition, we found evidence for the validity of Weber’s law with JNDs increasing linearly with increasing acceleration level. Interestingly, the multisensory data showed little evidence for effective cue integration of auditory information in this setup. These findings lay the groundwork for a better understanding of how different modalities work together in acceleration perception.

This paper describes the process of design, analysis, and scoring with both subjective and objective criteria, of a set of possible haptic inceptors configurations to be used as primary flight control devices for a class of future tilt rotor vehicles. Several scoring criteria were adopted like ergonomics, cognitive compatibility, easiness of recovery in fault situations, and expected workload among several others. Each criterion was weighted to obtain a scoring matrix for a total of 18 different configurations, some "classic", some novel, leading to an overall ranking. The matrix was used to select the best candidate configurations to be tested using a human-in-the-loop simulator in the context of the EU Funded CleanSky2 SMAR-TeR Project. After a final review phase, the best solution will be adopted to actually fly the Leonardo NextGen Civil Tilt Rotor Technological Demonstrator in the context of the EU Funded CleanSky2 SAIS Project.

Illusory self-motion often provokes motion sickness, which is commonly explained in terms of an inter-sensory conflict that is not in accordance with previous experience. Here we address the influence of cognition in motion sickness and show that such a conflict is not provocative when the observer believes that the motion illusion is indeed actually occurring. Illusory self-motion and motion sickness were elicited in healthy human participants who were seated on a stationary rotary chair inside a rotating optokinetic drum. Participants knew that both chair and drum could rotate but were unaware of the actual motion stimulus. Results showed that motion sickness was correlated with the discrepancy between participants’ perceived self-motion and participants’ beliefs about the actual motion. Together with the general motion sickness susceptibility, this discrepancy accounted for 51% of the variance in motion sickness intensity. This finding sheds a new light on the causes of visually induced motion sickness and suggests that it is not governed by an inter-sensory conflict per se, but by beliefs concerning the actual self-motion. This cognitive influence provides a promising tool for the development of new countermeasures.

In dynamic driving simulators, the experience of operating a vehicle is reproduced by combining visual stimuli generated by graphical rendering with inertial stimuli generated by platform motion. Due to inherent limitations of the platform workspace, inertial stimulation is subject to shortcomings in the form of missing cues, false cues, and/or scaling errors, which negatively affect simulation fidelity. In the present study, we aim at quantifying the relative contribution of an active somatosensory stimulation to the perceived intensity of self-motion, relative to other sensory systems. Participants judged the intensity of longitudinal and lateral driving maneuvers in a dynamic driving simulator in passive driving conditions, with and without additional active somatosensory stimulation, as provided by an Active Seat (AS) and Active Belts (AB) integrated system (ASB). The results show that ASB enhances the perceived intensity of sustained decelerations, and increases the precision of acceleration perception overall. Our findings are consistent with models of perception, and indicate that active somatosensory stimulation can indeed be used to improve simulation fidelity.

Previous literature suggests a relationship between individual characteristics of motion perception and the peak frequency of motion sickness sensitivity. Here, we used well-established paradigms to relate motion perception and motion sickness on an individual level. We recruited 23 participants to complete a two-part experiment. In the first part, we determined individual velocity storage time constants from perceived rotation in response to Earth Vertical Axis Rotation (EVAR) and subjective vertical time constants from perceived tilt in response to centrifugation. The cross-over frequency for resolution of the gravito-inertial ambiguity was derived from our data using the Multi Sensory Observer Model (MSOM). In the second part of the experiment, we determined individual motion sickness frequency responses. Participants were exposed to 30-minute sinusoidal fore-aft motions at frequencies of 0.15, 0.2, 0.3, 0.4 and 0.5 Hz, with a peak amplitude of 2 m/s2 in five separate sessions, approximately 1 week apart. Sickness responses were recorded using both the MIsery SCale (MISC) with 30 s intervals, and the Motion Sickness Assessment Questionnaire (MSAQ) at the end of the motion exposure. The average velocity storage and subjective vertical time constants were 17.2 s (STD = 6.8 s) and 9.2 s (STD = 7.17 s). The average cross-over frequency was 0.21 Hz (STD = 0.10 Hz). At the group level, there was no significant effect of frequency on motion sickness. However, considerable individual variability was observed in frequency sensitivities, with some participants being particularly sensitive to the lowest frequencies, whereas others were most sensitive to intermediate or higher frequencies. The frequency of peak sensitivity did not correlate with the velocity storage time constant (r = 0.32, p = 0.26) or the subjective vertical time constant (r = − 0.37, p = 0.29). Our prediction of a significant correlation between cross-over frequency and frequency sensitivity was not confirmed (r = 0.26, p = 0.44). However, we did observe a strong positive correlation between the subjective vertical time constant and general motion sickness sensitivity (r = 0.74, p = 0.0006). We conclude that frequency sensitivity is best considered a property unique to the individual. This has important consequences for existing models of motion sickness, which were fitted to group averaged sensitivities. The correlation between the subjective vertical time constant and motion sickness sensitivity supports the importance of verticality perception during exposure to translational sickness stimuli.

Percepts of verticality are thought to be constructed as a weighted average of multisensory inputs, but the observed weights differ considerably between studies. In the present study, we evaluate whether this can be explained by differences in how visual, somatosensory and proprioceptive cues contribute to representations of the Head In Space (HIS) and Body In Space (BIS). Participants (10) were standing on a force plate on top of a motion platform while wearing a visualization device that allowed us to artificially tilt their visual surroundings. They were presented with (in)congruent combinations of visual, platform, and head tilt, and performed Rod & Frame Test (RFT) and Subjective Postural Vertical (SPV) tasks. We also recorded postural responses to evaluate the relation between perception and balance. The perception data shows that body tilt, head tilt, and visual tilt affect the HIS and BIS in both experimental tasks. For the RFT task, visual tilt induced considerable biases (≈ 10° for 36° visual tilt) in the direction of the vertical expressed in the visual scene; for the SPV task, participants also adjusted platform tilt to correct for illusory body tilt induced by the visual stimuli, but effects were much smaller (≈ 0.25°). Likewise, postural data from the SPV task indicate participants slightly shifted their weight to counteract visual tilt (0.3° for 36° visual tilt). The data reveal a striking dissociation of visual effects between the two tasks. We find that the data can be explained well using a model where percepts of the HIS and BIS are constructed from direct signals from head and body sensors, respectively, and indirect signals based on body and head signals but corrected for perceived neck tilt. These findings show that perception of the HIS and BIS derive from the same sensory signals, but see profoundly different weighting factors. We conclude that observations of different weightings between studies likely result from querying of distinct latent constructs referenced to the body or head in space.

The risk of motion sickness is considerably higher in autonomous vehicles than it is in human-operated vehicles. Their introduction will therefore require systems that mitigate motion sickness. We investigated whether this can be achieved by augmenting the vehicle interior with additional visualizations. Participants were immersed in motion simulations on a moving-base driving simulator, where they were backward-facing passengers of an autonomous vehicle. Using a Head-Mounted Display, they were presented either with a regular view from inside the vehicle, or with augmented views that offered additional cues on the vehicle's present motion or motion 500ms into the future, displayed on the vehicle's interior panels. In contrast to the hypotheses and other recent studies, no difference was found between conditions. The absence of differences between conditions suggests a ceiling effect: providing a regular view may limit motion sickness, but presentation of additional visual information beyond this does not further reduce sickness.

To determine own upright body orientation the brain creates a sense of verticality by a combination of multisensory inputs. To test whether this process is affected by aging, we placed younger and older adults on a motion platform and systematically tilted the orientation of their visual surroundings by using an augmented reality setup. In a series of trials, participants adjusted the orientation of the platform until they perceived themselves to be upright. Tilting the visual scene around the roll axis induced a bias in subjective postural vertical determination in the direction of scene tilt in both groups. In the group of older participants, however, the observed peak bias was larger and occurred at larger visual tilt angles. This indicates that the susceptibility to visually induced biases increases with age, possibly caused by a reduced reliability of sensory information.

The goal of new adaptive technologies is to allow humans to interact with technical devices, such as robots, in natural ways akin to human interaction. Essential for achieving this goal, is the understanding of the factors that support natural interaction. Here, we examined whether human motor control is linked to the visual appearance of the interaction partner. Motor control theories consider kinematic-related information but not visual appearance as important for the control of motor movements (Flash & Hogan, 1985; Harris & Wolpert, 1998; Viviani & Terzuolo, 1982). We investigated the sensitivity of motor control to visual appearance during the execution of a social interaction, i.e. a high-five. In a novel mixed reality setup participants executed a high-five with a three-dimensional life-size human- or a robot-looking avatar. Our results demonstrate that movement trajectories and adjustments to perturbations depended on the visual appearance of the avatar despite both avatars carrying out identical movements. Moreover, two well-known motor theories (minimum jerk, two-thirds power law) better predict robot than human interaction trajectories. The dependence of motor control on the human likeness of the interaction partner suggests that different motor control principles might be at work in object and human directed interactions.

Even when we are wearing gloves, we can easily detect whether a surface that we are touching is sticky or not. However, we know little about the similarities between brain activations elicited by this glove contact and by direct contact with our bare skin. In this functional magnetic resonance imaging (fMRI) study, we investigated which brain regions represent stickiness intensity information obtained in both touch conditions, i.e., skin contact and glove contact. First, we searched for neural representations mediating stickiness for each touch condition separately and found regions responding to both mainly in the supramarginal gyrus and the secondary somatosensory cortex. Second, we explored whether surface stickiness is encoded in common neural patterns irrespective of how participants touched the sticky stimuli. Using a cross-condition decoding method, we tested whether the stickiness intensities could be decoded from fMRI signals evoked by skin contact using a classifier trained on the responses elicited by glove contact, and vice versa. Our results found shared neural encoding patterns in the bilateral angular gyri and the inferior frontal gyrus (IFG) and suggest that these areas represent stickiness intensity information regardless of how participants touched the sticky stimuli. Interestingly, we observed that neural encoding patterns of these areas were reflected in participants’ intensity ratings. This study revealed common and distinct brain activation patterns of tactile stickiness using two different touch conditions, which may broaden the understanding of neural mechanisms related to surface texture perception.

Inertial motions may be defined in terms of acceleration and jerk, the time-derivative of acceleration. We investigated the relative contributions of these characteristics to the perceived intensity of motions. Participants were seated on a high-fidelity motion platform, and presented with 25 above-threshold 1 s forward (surge) motions that had acceleration values ranging between 0.5 and 2.5 m/s2 and jerks between 20 and 60 m/s3 in five steps each. Participants performed two tasks: a magnitude estimation task, where they provided subjective ratings of motion intensity for each motion, and a two-interval forced choice task, where they provided judgments on which motion of a pair was more intense, for all possible combinations of the above motion profiles. Analysis of the data shows that responses on both tasks may be explained by a single model, and that this model should include acceleration only. The finding that perceived motion intensity depends on acceleration only appears inconsistent with previous findings. We show that this discrepancy can be explained by considering the frequency content of the motions, and demonstrate that a linear time-invariant systems model of the otoliths and subsequent processing can account for the present data as well as for previous findings.

In motion simulation, motion input scaling is often applied to deal with the limited motion envelopes of motion simulators. In this research, the time-varying effects of scaling the lateral specific force up or down during passive curve driving in a car driving simulation are investigated through a simulator experiment. It is concluded that lateral specific force scaling has a time-varying effect on the perceived fidelity of a curve-driving simulation. In particular, motion scaling during a curve entry is found to be less detrimental than motion scaling during a curve’s sustained part and during the curve exit.

Objects learned within single enclosed spaces (e.g., rooms) can be represented within a single reference frame. Contrarily, the representation of navigable spaces (multiple interconnected enclosed spaces) is less well understood. In this study we examined different levels of integration within memory (local, regional, global), when learning object locations in navigable space. Participants consecutively learned two distinctive regions of a virtual environment that eventually converged at a common transition point and subsequently solved a pointing task. In Experiment 1 pointing latency increased with increasing corridor distance to the target and additionally when pointing into the other region. Further, when pointing within a region alignment with local and regional reference frames, when pointing across regional boundaries alignment with a global reference frame was found to accelerate pointing. Thus, participants memorized local corridors, clustered corridors into regions, and integrated globally across the entire environment. Introducing the transition point at the beginning of learning each region in Experiment 2 caused previous region effects to vanish. Our findings emphasize the importance of locally confined spaces for structuring spatial memory and suggest that the opportunity to integrate novel into existing spatial information early during learning may influence unit formation on the regional level. Further, global representations seem to be consulted only when accessing spatial information beyond regional borders. Our results are inconsistent with conceptions of spatial memory for large scale environments based either exclusively on local reference frames or upon a single reference frame encompassing the whole environment, but rather support hierarchical representation of space. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Virtual Reality supports collaboration among partners across departments and fields, independent of physical boundaries. Virtual reality applications can solve the time and cost consuming logistic problem that companies encounter when sending experts to remote locations. However, it is not yet clear how effective partners collaborate when in remote locations. In one experiment, we examined whether partners who are physically in the same room and interact with each other before they start collaborating affects performance compared to collaborators who meet and interact only within the virtual space. Participants had to solve a Rubik's cube type three-dimensional puzzle by arranging cubes that varied in color within a solution space in such a way, so that each side of the solution space showed a single color. Participants were immersed within a virtual environment and in one condition participants were collocated in the same room (local condition), while in the other one they were located in different rooms (remote condition). Results showed that collaborators in both conditions successfully completed the task but performance was better during the local compared to the remote condition.

This paper describes a driving simulation experiment, executed on the Daimler Driving Simulator (DDS), in which a filter-based and an optimization-based motion cueing algorithm (MCA) were compared using a newly developed motion cueing quality rating method. The goal of the comparison was to investigate whether optimization-based MCAs have, compared to filter-based approaches, the potential to improve the quality of motion simulations. The paper describes the two algorithms, discusses their strengths and weaknesses and describes the experimental methods and results. The MCAs were compared in an experiment where 18 participants rated the perceived motion mismatch, i.e., the perceived mismatch between the motion felt in the simulator and the motion one would expect from a drive in a real car. The results show that the quality of the motion cueing was rated better for the optimization-based MCA than for the filter-based MCA, indicating that there exists a potential to improve the quality of the motion simulation with optimization-based methods. Furthermore, it was shown that the rating method provides reliable and repeatable results within and between participants, which further establishes the utility of the method.

Creating metrically accurate avatars is important for many applications such as virtual clothing try-on, ergonomics, medicine, immersive social media, telepresence, and gaming. Creating avatars that precisely represent a particular individual is challenging however, due to the need for expensive 3D scanners, privacy issues with photographs or videos, and difficulty in making accurate tailoring measurements. We overcome these challenges by creating "The Virtual Caliper", which uses VR game controllers to make simple measurements. First, we establish what body measurements users can reliably make on their own body. We find several distance measurements to be good candidates and then verify that these are linearly related to 3D body shape as represented by the SMPL body model. The Virtual Caliper enables novice users to accurately measure themselves and create an avatar with their own body shape. We evaluate the metric accuracy relative to ground truth 3D body scan data, compare the method quantitatively to other avatar creation tools, and perform extensive perceptual studies. We also provide a software application to the community that enables novices to rapidly create avatars in fewer than five minutes. Not only is our approach more rapid than existing methods, it exports a metrically accurate 3D avatar model that is rigged and skinned.

Distinguishing animate from inanimate objects is fundamental for social perception in humans and animals. Visual motion cues indicative of self-propelled object motion are useful for animacy perception: they can be detected over a wide expanse of visual field, at distance and in low visibility conditions, can attract attention and provide clues about object behaviour. However, the neural correlates of animacy perception evoked exclusively by visual motion cues, i.e. not relying on form, background or visual context, are unclear. We aimed to address this question in four psychophysical experiments in humans, two of which performed during neuroimaging. The stimulus was a single dot with constant form that moved on a blank background and evoked controlled degrees of perceived animacy through parametric variations of self-propelled motion cues. BOLD signals reflecting perceived animacy in a graded manner irrespective of eye movements were found in one intraparietal region. Additional whole-brain and region-of-interest analyses revealed no comparable effects in brain regions associated with social processing or other areas. Our study shows that animacy perception evoked solely by visual motion cues, a basic perceptual process in social cognition, engages brain regions not primarily associated with social cognition.