# Spatial Compatibility and Intersensory Conflicts in Teleoperation: Impact on Object Orientation Control in Virtual Reality

Lefebvre Maëlis, Bolina Rei João, López-Contreras González, Elena, Roy Raphaëlle N., Peysakhovich Vsevolod

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Lefebvre Maëlis, Bolina Rei João, López-Contreras González, Elena, Roy Raphaëlle N., Peysakhovich Vsevolod. Spatial Compatibility and Intersensory Conflicts in Teleoperation: Impact on Object Orientation Control in Virtual Reality. Association for Computing Machinery (ACM), 2025, 14 (4). hal-05510788

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Spatial Compatibility and Intersensory Conflicts in
Teleoperation: Impact on Object Orientation Control in
Virtual Reality

MAËLIS LEFEBVRE, JOÃO BOLINA REI, ELENA LÓPEZ-CONTRERAS GONZÁLEZ, RAPHAËLLE N. ROY, and VSEVOLOD PEYSAKHOVICH, Fédération ENAC ISAE-SUPAERO

ONERA, Université de Toulouse, Toulouse, France

The study investigates the impact of vestibular and somatosensory gravceptive signals on spatial perception and motor planning/control. Specifically, it explores the consequences of spatial compatibility between (1) the tilts of an observer's body and those of an object perceived in virtual reality, and (2) the directions of body rotation and manual movements, on visual perception and object orientation control. We hypothesize that intersensory conflicts resulting from performing a task with a head-mounted display while tilted may increase susceptibility to spatial incompatibilities, further impairing teleoperation performance. Fifty-four participants controlled and estimated the orientation of an object in virtual reality while their body tilt and movement could be spatially compatible or incompatible with the object's orientation and manual movement direction. The results indicate that spatial incompatibilities between the direction of participants' whole-body rotation and manual movement negatively impacted the control of the object orientation, as indexed by accuracy, precision, and response times. Moreover, body roll tilt decreased operators' confidence in their visual perception of the remotely controlled object, surprisingly only in spatially compatible conditions. These findings highlight teleoperation challenges in dynamic environments. Research on countermeasures for safer teleoperation is essential for field advancement.

CCS Concepts: • Human-centered computing → Empirical studies in HCI;

Additional Key Words and Phrases: Body motion, body tilt, sensory-motor tasks, subjective vertical, virtual reality, teleoperation, situational awareness

**ACM Reference format:**

Maëlis Lefebvre, João Bolina Rei, Elena López-Contreras González, Raphaëlle N. Roy, and Vsevolod Peysakhovich. 2025. Spatial Compatibility and Intersensory Conflicts in Teleoperation: Impact on Object Orientation Control in Virtual Reality. *ACM Trans. Hum.-Robot Interact.* 14, 4, Article 62 (July 2025), 16 pages.
https://doi.org/10.1145/3724132

This work has been supported by the European Space Agency (ESA, EISI agreement number 4000134484) and the French National Centre for Space Studies (CNES).

Authors' Contact Information: Maëlis Lefebvre (corresponding author), Fédération ENAC ISAE-SUPAERO ONERA, Université de Toulouse, Toulouse, France; e-mail: maelis.lefebvre@isae-supaero.fr; João Bolina Rei, Fédération ENAC ISAE-SUPAERO ONERA, Université de Toulouse, Toulouse, France; e-mail: jpbr@live.com.pt; Elena López-Contreras González, Fédération ENAC ISAE-SUPAERO ONERA, Université de Toulouse, Toulouse, France; e-mail: elena.lopez-contreras-gonzalez@isae-supaero.fr; Raphaëlle N. Roy, Fédération ENAC ISAE-SUPAERO ONERA, Université de Toulouse, Toulouse, France; e-mail: raphaëlle.roy@isae-supaero.fr; Vsevolod Peysakhovich, Fédération ENAC ISAE-SUPAERO ONERA, Université de Toulouse, Toulouse, France; e-mail: vsevolod.peysakhovich@isae-supaero.fr.
# 1 Introduction

In visuomotor tasks and during interactions with complex systems, the compatibility—in other words, the harmonious relationship—between what is perceived (stimuli) and how to respond to it (response) can influence human performance [22, 45, 47, 56]. Several effects illustrate the importance of these stimulus-response compatibilities, such as the well-known Stroop [57] or Flanker [20] effects. The specific effect of interest here is spatial compatibility effect between the stimulus and response, also known as the Simon effect [52, 53].

## 1.1 Spatial Compatibility Effects

It has been shown that the compatibility between stimulus and response can be based on their spatial characteristics (see [28] for an overview); people respond faster and more accurately when the stimulus and response (featuring directional cues) are presented in the same location. This effect persists even when a distractor conveys spatial characteristics and is presented in a different sensory modality (e.g., an auditory distractor in a visuomotor task). For example, participants respond more quickly to a light presented on the right side of a screen when it is accompanied by a tone in the right ear, compared to a tone in the left ear [51, 52]. Simon attributed this phenomenon to an automatic tendency to “react toward the source of the stimulation,” even when the stimulus location is irrelevant to the task. Interestingly, these spatial compatibility effects have also been observed in interactions with more complex systems, such as during tool use [31, 46].

With technological advancements, operators can now interact with systems in dynamic environments, such as moving vehicles. This is the case onboard autonomous vehicles [1, 14], in mobile tactical operations centers (e.g., manned ground vehicles; [37]), or onboard helicopters as part of future military projects such as the Future Combat Air System, which aims to integrate manned-unmanned teaming [2, 4]. In such contexts, operators may control systems while their bodies are inclined and in motion. Under these conditions, the operator's body tilt provides directional cues that depend on the direction of inclination.

This raises the question of whether body tilt could elicit spatial compatibility effects similar to those observed with irrelevant auditory distractors [52], potentially affecting response times in a visuomotor task. To our knowledge, this question remains unexplored. However, numerous studies suggest that body tilt influences sensorimotor abilities (as discussed below). Therefore, consistent with Simon's paradigms, we hypothesize that incompatibilities between body tilt direction and response orientation will further impair performance compared to compatible conditions.

## 1.2 Verticality Perception and the Impact of Body Tilt on Sensorimotor Abilities

To efficiently interact, navigate, and orient ourselves in space, accurate perception of the “up” direction, as well as of the body’s orientation and movement in the environment, is essential. In addition, generating a successful motor command requires awareness of the gravity-related constraints that apply to actuators during action. This process involves determining the direction and intensity of gravitational force, as well as assessing our body’s position relative to this geocentric reference. Graviception—the perception of gravity orientation—results from a multistory integration [21, 55]. Visual cues, such as the orientation of trees, buildings, the horizon, and celestial bodies such as the sun and stars, provide insights into the gravity vector’s orientation. The otolith organs within the vestibular system serve as a biological “plumb line,” providing the position of the head in relation to gravity [5]. In addition, inputs from the somesthetic system, originating from muscular, articulary, cutaneous, and visceral organ receptors, contribute to the estimation of the gravity vector. These diverse sensory cues are integrated at the brain level and appear associated with
frames of reference crucial for shaping spatial perception. These frames of reference can be body-centered (egocentric), defined by the observer environment (allocentric), or by gravitational force (geocentric).

Human evolution has led to the alignment of our head and body axes with the Earth's gravitational forces. Literature reveals that when humans deviate from an upright position, their cognitive processes become less effective, and sensorimotor abilities may be impaired.

For instance, in an upright position, without visual cues, humans can still align a luminous rod with the vertical (Subjective Visual Vertical [SVV] test) with an accuracy of less than 1° [58]. However, when tilted, they experience a perception bias. The SVV shifts toward the tilt/body axis (underestimation of a significant tilt, Aubert or A-effect [3]), or in the opposite direction (overestimation of a small tilt, Müller or E-effect [44]). The larger the tilt, the more they reorient the SVV toward our body axis. Mittelstaedt [41] suggested that the A-effect is linked to the idiotropic vector, which represents the internal bias that tends to assume that both the head and vertical axes should be aligned. Similarly, in the Subjective Haptic Vertical test, tilted humans also struggle to manually orient a real rod in the direction of gravity [25, 49].

When visual cues indicating the direction of the vertical are available and aligned with the retina, but the body is tilted, graviceptive inputs become incongruent. The internal (vestibular and somatosensorial/proprioceptive) and external (visual) graviceptive inputs yield different estimates of the vertical direction, resulting in intersensory conflicts. Surprisingly, in such situations, the “right way up” deviates from the physical vertical, the SVV, or the body axis. Instead, it aligns with another orientation termed the Perceptual Upright, as defined by Dyde et al. [19]. This orientation facilitates the easiest recognition of objects and seems to be influenced by all body, gravity, and visual background orientations.

Furthermore, body tilt affects the perception and reproduction of horizontal orientations. When upright, the oblique effect demonstrates our ability to estimate both vertical and horizontal orientations. However, when the body is tilted, the oblique effect disappears, and once again the subject's subjective vertical appears to be processed with better accuracy and precision than all other orientations [35].

Aside from altering the perception of the environment's orientations, the tilted body position leads to object misperceptions. Graviceptive cues play a role in modeling the effects of gravity on a moving target. Consequently, the perception of an object's motion and acceleration [42] as well as its interception timing, can be affected when the observer's body is tilted [32]. In a study by Kim et al. [29], it was observed that objects appear larger or closer when lying down, suggesting that this phenomenon “may provide survival benefits in such a vulnerable position.”

Furthermore, precise manual control requires the integration of the environmental cues, the observer body's orientation cues, and an estimation of the effects of gravity on the actuators. Microgravity studies show that the central nervous system uses an internal model of gravity that does not immediately update itself during capture movements [38] or grip force adjustment tasks [16, 17]. However, on Earth, results remain controversial as to the adaptation of action when the body or head is misaligned with respect to gravity. Some studies report diminished performance in eye-hand coordination tasks [6, 59], pointing hand and arm pointing movements [50, 54, 59], or estimating the position of their hand [26]. Others, on the other hand, observed no significant differences between the upright and tilted body positions [8, 24].

## 1.3 The Present Study

Although some work has been initiated to assess the body tilt's impact on various cognitive processes, vertical perception, and manual response, to the best of our knowledge, no studies have explored the influence of spatial (in)compatibility between the body's tilt direction and that of the
response on their manual control, orientation perception, and confidence at the behavioral level. To address this gap, we designed a straightforward visuomotor task in virtual reality that participants had to perform while seated on a motion platform. The task consisted of the remote control and the orientation estimation of a rover's panels (presented as ego-centered). Participants' body tilt and movement could be spatially compatible or incompatible with the direction of the panels' orientation. After each trial, participants reported their confidence levels in their responses. Before performing this task, the SVV test was performed. This allowed to (1) ensure that the experimental setup/chair tilt did induce an alteration of the perception of the vertical and (2) confirm that our participants had no inner ear damage that could bias the data.

We have formulated two hypotheses regarding the impact of spatial incompatibilities on participants' performance. Our first hypothesis posits that such incompatibilities between the participant's whole-body rotation and their manual movement directions would decrease their manual control accuracy, precision, and response times. The second hypothesis suggests that spatial incompatibilities between the participant's body tilt and the teleoperated object's orientation would lead to reduced accuracy and increased response time in estimating the object's orientation, as well as decreased post-choice confidence.

# 2 Methods

## 2.1 Subjects

A total of 54 healthy volunteers, students, and staff of the French Aerospace Engineering School ISAE-SUPAERO, participated in the study (12 females, mean age = 27.5, SD = 9.6). All participants had normal or corrected-to-normal vision, with no reported history of neurological, psychiatric diseases, severe motion sickness, or regular use of medication.

*Ethics Statement.* All volunteers were informed of their rights and provided written informed consent for participation in the study, according to the Declaration of Helsinki. The research protocol was approved by the Comité d'Éthique de la Recherche-CER at Université de Toulouse (CER number 2022-482).

## 2.2 Experimental Device

The study was conducted in the VR research room within the French Aerospace Engineering School ISAE-SUPAERO. Participants were placed on a motion platform (VRtigo 6-axis movement platform, PS-6TM-150, MotionSystems), in a dark environment (no visual cue indicating their body orientation), with a VR headset (HTC Vive Pro) and a gamepad (Logitech gamepad F310) (Figure 1).

## 2.3 Study Design and Procedure

The study involved three virtual reality tasks (developed in Unity3D/C#) that participants performed while a motion platform modulated their body orientation and movement. All visual presentations of tasks were egocentric; in other words, they were tilted with the body rotation. It should be noted that this experimental protocol uses several angles of inclination to measure the potential effect of the amplitude of body inclination. However, these analyses were not conducted for the present study.

First, participants performed a SVV test (Figure 2), followed by a manual-control and perception tasks (Figure 3). The SVV was composed of 10 training trials and 10 task trials, the manual-control and perception task of 20 training trials, and 60 task trials, distributed across two sessions of 30 trials each. During the study, participants had several 5-minute breaks. The experiment consisted of a total of 100 trials (training and task) and lasted approximately 45 minutes. Before the main
<figure><img src="image_3.png" /><figcaption>Fig. 1. Experimental setup with the motion platform, the VR headset, and the gamepad placed on the participant's knees.</figcaption></figure>

experiment, participants were familiarized with all parts of the tasks. A short training sequence, including feedback, for all tasks along with instructions, was provided. Each trial began with a neutral chair position (Figure 3(a)).

**SVV Test.** The SVV test (Figure 2) was designed to evaluate the effect of body orientation on participants’ SVV. Participants were tilted in five possible orientations (0°, 12°, 24° to the right (12R, 24R) and left (12L, 24L)), rotated in the roll axis. When oriented, participants had to align a human pictogram with the direction of the room’s vertical, as discerned through their vestibular and proprioceptive sensations. To facilitate comprehension of verticality, participants were instructed to orient the figure as they imagined a person would stand in the room in front of them. Using the right pad (via right and left thumb movements) on the gamepad, participants rotated the figure and confirmed their response by pressing the right trigger pad. After each response, the figure turned yellow, inviting the participants to indicate their confidence level by adjusting (up and down thumb movements on the right pad) a green cursor. A greener figure indicated higher confidence. The manual-control and perception tasks (Figure 3) consisted of multiple trials of participant orientation in one of the five possible orientations, manual-control task while the participant’s body is in movement, perception task in a body orientation (no movement), and subsequent confidence rating.

**Manual-Control Task.** The manual-control task (Figure 3(a)) was designed to evaluate the effect of compatibility between the body movement and manual-control directions. Therefore, in this task, participants were required to manipulate the tilt of the rover’s panels using the gamepad while their body was moved in five possible orientations (0°, 12°, 24° to the right and left), rotated in the roll axis. Before chair movement, participants were presented with an “A,” “B,” or “C” instruction. During chair movement, they were instructed to either center the rover’s panels horizontally (“C”)
<figure><img src="image_4.png" /><figcaption>Fig. 2. SVV test. The time course of one trial with (a) five possible body orientations, (b) the SVV test associated with (c) confidence rating (the greener the figure was, the more confident the participants were), and (d) feedback on the orientation of the physical vertical represented by the orange line, for training trials only. Then, the motion platform moved back to its upright neutral position.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig. 3. Manual-control and perception tasks. An example of the time course of a spatially incompatible trial with (a) the manual-control task performed during the chair roll tilt movement to the target angle (here the participant had to align the panels with the “B” rod), (b) 2 seconds of transition between the tasks, (c) the perception task performed during the static tilt of the chair associated with confidence rating (the greener the arrow was, the more confident the participants were), then (d) the motion platform moved back to its upright neutral position.</figcaption></figure>

or align the panels with a rod tilted at 20° to the right (“A”) or to the left (“B”), maintaining the specified position until the rover disappears (Figure 4).

*Perception Task*. The perception task (Figure 3(c)) was designed to evaluate the effect of compatibility between the body orientation and the teleoperated object’s orientation on the perception of the
Spatial Compatibility and Intersensory Conflicts in Teleoperation

<figure><img src="image_6.png" /><figcaption>Fig. 4. Manual-control task. An example of a trial in which the participant had to align panels with the B rod. (a) The rover's panels are in an initial position, and the "B" instruction is displayed in front of the rover, prompting the participant to align the panel with the "B" rod (here illuminated in green). (b) After the instruction vanished, the participant tilted the panel to the left to ensure its right side aligned with the "B" rod.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 5. Spatial compatibility conditions: In spatially compatible conditions, the participant's entire body and manual movements were aligned in the same direction (manual-control task) and the participant's body and the rover's panels were tilted in the same direction (perception task). In spatially incompatible conditions, the body movement and tilt were in opposite directions to those of the manual control and panel orientation, respectively. The body tilts could reach target angles of 12° or 24° to the right or left.</figcaption></figure>

object's orientation. The expected position of the rover's panels in the manual-control task was displayed for 1 second. The screen was then cleared, and participants were asked to align an arrow with the panel's perpendicular (right and left thumb movements to rotate the arrow) while being in one of the five possible body orientations. Then, as in the SVV test, participants indicated their level of confidence after each trial.

*Spatial Compatibility Conditions.* The movement and perception tasks were executed under three experimental conditions: the control, spatially compatible, and incompatible conditions (Figure 5). In the control conditions, participants performed the movement and perception tasks in an upright sitting position with no body movement or induced tilt. In spatially compatible conditions, both the participant's whole-body and manual movements were in the same direction (manual-control task) and the participant's body and the rover's panels' were tilted in the same direction (perception task). Whereas in spatially incompatible conditions, the body movement and tilt were in opposite directions to those of the manual control and panel orientation, respectively.
## 2.4 Data Processing and Statistical Analyses

We explored the impact of the spatial compatibility between the participants' body tilt direction and that of the response on their manual control, orientation perception as well as post-choice confidence within a simple virtual reality task. To validate the functionality of our setup concerning alterations in participants' vertical perception, we conducted an SVV test. Thus, for orientation perception tasks of both the vertical and the teleoperated object (perception and SVV tasks), we analyzed response accuracy (i.e., **Angle Error (AE)** in indicated orientations), response time, and the participants' confidence in their visual perception. During rovers' panels' control (manual-control task) we examined response accuracy (i.e., the average position of the panel angle in the last 5 seconds of trials, with 1 as the target angle to be reached), precision (i.e., motor responses' SD during manual control in the last 5 seconds of trials) and response time (start of manual movement and the time to reach 50% of their response angle). Two outliers were excluded from the analysis of the perception task due to a misunderstanding of the task instructions.

Data preprocessing was performed using Python programming. SVV data were analyzed using a 1-way repeated measures ANOVA with participant orientation (L12, L24, R12, R24, and 0) as a grouping factor. Movement and Perception tasks data were analyzed using a one-way repeated measures ANOVA with Spatial compatibility (Compatible and Incompatible) as a factor. Violations of the assumption of sphericity assessed by Mauchly's Test of Sphericity were in all ANOVA corrected for by using Greenhouse-Geisser corrections. All *post hoc* analyses were performed with a Bonferroni correction.

Supplementary analyses regarding the effects of body tilt, movement, and panel orientations on participants' response times, perception, and manual accuracy as well as their post-choice confidence are presented in the supplementary material. Data analyses were made using a two-way repeated measures ANOVA with participant orientation (L12, L24, R12, R24, and 0) and Panel orientation (Right, Left, and Center) as grouping factors. Violations of the assumption of sphericity assessed by Mauchly's Test of Sphericity were in all ANOVA also corrected for by using Greenhouse-Geisser corrections. All *post hoc* analyses were performed with a Bonferroni correction.

## 3 Results

*SVV Test.* In the SVV test, the participants' orientation elicited statistically significant changes in participants' confidence ($F_{3.2,161.9} = 50, p < .001, \eta_p^2 = .49$, Figure 6(a)), response times ($F_{3.4,172.2} = 10.3, p < .001, \eta_p^2 = .17$, Figure 6(b)), and accuracy ($F_{2.9,148.4} = 3.2, p = .027, \eta_p^2 = .059$, Figure 6(c)). *Post hoc* analyses revealed that participants were less confident when tilted (p < .001) and that participants were more confident when tilted 12° to the left than when tilted 12° and 24° to the right (p < .001 and p = .007 respectively). They also had longer response times when tilted to the right and to the left (p < .001 and p < .01 respectively) and had a decreased accuracy when tilted to the right only (p = .05).

*Effect of Tilt Compatibility—Perception Task.* In the perception task, the spatial compatibility between the tilts of the participant and the object elicited statistically significant changes in confidence ($F_{1,53} = 4.8, p = .033, \eta_p^2 = .087$, Figure 7(c)). Participants were less confident during compatible conditions. However, no significant main effect of compatibility was found for accuracy (Figure 7(a)) nor response time (Figure 7(b)).

*Effect of Movement Direction Compatibility—Manual-Control Task.* In the manual-control task, the spatial compatibility between the direction of the participants' whole-body and manual movements elicited statistically significant changes in their accuracy ($F_{1,53} = 10.7, p = .002, \eta_p^2 = .168$, Figure 8(a)), precision ($F_{1,53} = 4.57, p = .037, \eta_p^2 = .079$, Figure 8(b)), and response times ($F_{1,53} = 4,$
Spatial Compatibility and Intersensory Conflicts in Teleoperation

<figure><img src="image_8.png" /><figcaption>Fig. 6. Results of the SVV test. Effect of the body tilt on (a) confidence, (b) response time, and (c) accuracy. Accuracy corresponds to the absolute AE for indicated orientations. Error bars represent the S.E. (***p < .001, **p < .01, *p < .05).</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>Fig. 7. Results of the perception task: Effect of spatial compatibility between the tilts of the observer's body and that of the object on (a) accuracy, (b) response time, and (c) the confidence participants had in their responses. Accuracy corresponds to the absolute AE for indicated orientations. Error bars represent the S.E. (*p < .05).</figcaption></figure>

p = .049, $\eta_p^2$ = .071, Figure 8(c)). Incompatible conditions induced decreased accuracy and precision, and participants took longer to reach 50% of their response angle during the remote operation of the rover's panels. However, no significant main effect of spatial compatibility was found regarding the time participants took to start the manual movement ($F_{1,53} = 1.75, p = .19, \eta_p^2 = .032$).

# 4 Discussion

In this study, we introduced a new cognitive task to investigate how spatial (in)compatibilities between the participants' body roll tilts and movement could differently impact their perception and manual control of a remotely controlled object. The main findings confirmed our expectations, indicating that spatial incompatibilities between participants' whole-body and manual movement directions negatively impacted their manual control performance (accuracy, precision, and response times). In addition, body roll tilts reduced the confidence participants had in their visual perception of the remotely controlled object, albeit surprisingly, only in compatible conditions. Contrary to our hypotheses, spatial compatibility did not affect the perception of the orientation of the teleoperated object *per se*. These results, their implications, and their limits are further discussed below.
<figure><img src="image_10.png" /><figcaption>Fig. 8. Results of the manual-control task: Effect of spatial compatibility between the direction of the participants' whole-body and manual movements on (a) accuracy, (b) precision, and (c) response time. The accuracy corresponded to the normalized average angle of the panel during the last 5 seconds of the trial, i.e., 1 corresponds to the target angle. Precision corresponds to motor responses' SD during manual control during the last 5 seconds of the trial. RT50 corresponds to the time to reach 50% of the final response angle. Error bars represent the S.E. (\*\*p < .01, \*p < .05).</figcaption></figure>

## 4.1 SVV Results

The SVV results validated our setup's operability altering the participants' vertical perception. The scores did not result in the exclusion of any participants due to inner ear damage. Although no specific hypotheses were formulated regarding the SVV, our findings unveiled an interesting pattern of left-sided spatial bias among the participants. During the SVV test, where the participants judged the orientation of the vertical while being tilted at various angles, they were faster and more confident when tilted to the left. These results are consistent with previous studies highlighting the presence of a leftward bias in healthy participants during visuospatial tasks, commonly referred to as the pseudo-neglect phenomenon [12].

## 4.2 Effect of Participants' Body Motion on Manual Control

Consistent with our hypotheses, spatial incompatibilities between the direction of body movement and manual control negatively impacted manual control performance. Incompatibilities in movement direction led to participants being less precise, less accurate, and taking more time to complete the initial phase of the manual movement. Notably, no previous study had precisely investigated how spatial compatibility between whole-body rotation and manual control movement direction impacts sensory-motor performance. These results are consistent with Simon and Craft's work [51], demonstrating that an irrelevant body movement distraction can impair manual control precision, accuracy, and response time. Furthermore, conflicts between sensory inputs generally decrease performance in visuomotor tasks [9–11, 13, 19, 23, 39, 40]. In this context, our results are also consistent with existing literature.

## 4.3 Effect of Observers' Body Tilt on Object Orientation Perception

Contrary to our expectations, spatial incompatibilities between body tilt and the remotely controlled object's orientations did not affect participants' orientation estimation, neither in terms of accuracy nor response times. However, being tilted did influence participants' post-choice confidence in the orientation estimation task, yet surprisingly only during congruent conditions. Lipshits [34] studied the oblique effect (i.e., the human tendency to better perceive vertical or horizontal visual stimuli compared to the oblique ones) in several body orientations close to ours (22.5° inclination to the vertical). The results showed that only the perception of vertical and horizontal orientations
(with the head/body axis as the frame of reference) was impaired when the participants were tilted. However, oblique lines were perceived equally well when participants were tilted and upright, which could explain the results of the present study. Indeed, in our analyses, we compare conditions where the panels were systematically oblique (with the head/body axis as the frame of reference). Authors explain these phenomena by the fact that the perception of orientations will be stored in both an egocentric frame of reference (linked to the axis of the body) and an allocentric frame of reference (linked to the perceived axis of gravity) when available. When the body is in a natural upright position, both reference frames are aligned. However, once the body is tilted, a conflict occurs between these two frames, which can result in uncertainty in the representation of vertical and horizontal orientations. Furthermore, it is important to note that in our study the body tilts did not exceed 24° which corresponds to a small tilt in comparison with other studies where the authors used 45° [6, 25] or 90° (i.e., supine, ventral or lateral lying positions) tilts [19, 29, 36, 42, 49].

## 4.4 Confidence Results

Post-choice confidence represents the probability that the perceptual decision made is correct based on available sensory evidence. Drugowitsch et al. [18] found that “bounded evidence accumulation explains decision accuracy, speed, and certainty.” Although a tilted participant wearing a head-mounted display (aligned with their head as a frame of reference) already experiences sensorial conflict, we hypothesized that under incompatible spatial conditions, the visuo-vestibular/somatosensory conflict would further challenge the visual afferents leading to a larger decrease in confidence. We did observe a spatial compatibility effect, but unexpectedly, participants showed a decreased confidence only when the body and the object were tilted in the same direction (i.e., spatially compatible conditions).

Several limitations within the experimental protocol could explain these results. Simon's task [52] was highly experimental and controlled, utilizing simplified auditory and visual stimuli, each with a unique and clear spatial characteristic. In contrast, our teleoperation task is more representative of real-life scenarios, as the visual stimuli and required responses are more complex. One consequence of this complexity is, unfortunately for us, the induction of several potential spatial connotations, which makes the compatible and incompatible conditions more ambiguous and less evident. For example, consider a situation we analyze as spatially compatible: when the subject and the panel were both tilted to the right. When the panel is tilted to the right, it aligns with the left rod and is primarily visible on the screen's left side (as the rover's body partially obscures the panel right side). Although the instructions given to the participants were to align the panels with A, B, or C rod (Figure 3(a)), and the laterality of the rods was never mentioned, the simple visualization of the panel aligned with the left bar and primarily visible on the left side of the screen may have induced an inverse spatial connotation. This could render the spatial connotations of our visual stimuli even more ambiguous or even reversed and explain why participants were less confident in spatially compatible conditions in the perception tasks. These results demonstrate the complexity of transferring phenomena observed in the laboratory to tasks that are more representative of reality, involving more complex stimuli and responses. Future studies using this experimental protocol must take these factors into account and modify the task to ensure accurate spatially compatible and incompatible conditions, especially for the perception task. One way to achieve this would be to incline not only the robot's panel but also the robot itself; in this way, spatial connotations will be less ambiguous.

Furthermore, it is important to note that a concept such as post-choice confidence could be influenced by high-level psychological factors, such as certain personality traits [30], and as a result, potentially impact our confidence measures. One way to address this would have been to use a validated post-choice confidence questionnaire, which could have lengthened the response time
in an uncomfortable position when the subject is inclined. Alternatively, if we wanted to keep this question, we could have included personality questionnaires measuring traits in order to control for these effects.

## 4.5 Considerations of Perspective in Teleoperation

Nowadays, through new technologies, we can perceive and control objects that have their own reference frames. To monitor or teleoperate a robot, an operator needs, through the robot's “eyes” and other sensors, to accurately estimate its position in space relative to the surrounding environment. When performing these tasks, the operator gets visual graviceptive information regarding the environment where the robot is operating and at the same time, he/she receives vestibular and somatosensorial graviceptive information from the place he/she operates the robot. In the case of remote operation from the ground, with an operator sitting in front of a control station, the orientation and position of the body are relatively constant. In such conditions, no conflict should arise that would deteriorate the teleoperation performance. However, some instances of teleoperation applications require the control of a remote robot from a moving vehicle, as seen in recent military projects such as the Future Combat Air System [2], which aims to pair manned and unmanned vehicles to execute specific missions and tasks. If an operator's body is tilted or in motion during teleoperation from dynamic and changing environments, i.e., from boats, helicopters, spacecraft, or any kind of moving vehicle, this will require operators to maintain situational awareness of the robot while disregarding gravitational changes in their own space. Our present work demonstrates that potential spatial incompatibilities between an operator's body rotation and its teleoperated object tilt may affect the fundamental manual control skills required for piloting. These issues need to be taken into account when designing future teleoperation control interfaces.

Conducting further research on the development of interfaces that give greater weight to the visual sensory information and/or enhance awareness of the robot's position and movement in its environment would be valuable. In this study, we simulated in virtual reality a teleoperation task using a third-person perspective view of the robot; meaning that the user sees the character from an external viewpoint. In many teleoperation scenarios, the remote environment is visualized through an onboard camera, corresponding to a first-person perspective [43]. However, the literature on human-robot and human-computer interaction suggests that the third-person perspective of the robot or avatar is better suited for navigation and dynamic tasks [6, 33, 47, 60] and enhances spatial awareness [15, 27, 61]. Therefore, further research on the impact of the remote-controlled robot's visual perspective on teleoperation performance in this dynamic context could, therefore, be a valuable approach to identifying an optimized interface.

## 4.6 Limitations

The present study had other more general limitations that should be taken into consideration when interpreting the results. (1) A first limitation is that our study group was not homogeneous as there were few women (N = 12) and left-handed (N = 4) individuals. (2) Furthermore, even though subjects understood the SVV task, the use of a simple rod instead of the human figure, as typically done in standard SVV tests, could have reduced the risk of misinterpretation regarding what the figure should align with—whether it be the body or the vertical axis. (3) In addition to the limitations mentioned in the discussion of the panels' orientation perception task results, we also did not consider the possibility that the afterimage of the stimulus may still be present on the retina. In a protocol asking for memorization and reproduction of visually perceived orientation similar to ours, the authors addressed this issue by displaying a distractor image consisting of many crossing lines at different orientations presented for 1 s between stimulus transitions [34]. (4) Also, the fact that subjects must, within a trial, first orient and then perceive the panels placed at the same
angle, could facilitate the perception of orientation since it was manually controlled at that angle beforehand. (5) Finally, when designing the study, we initially included several tilt angles to explore the impact of spatial compatibility between body and robot orientation at different degrees of tilt. This was intended to support an exploratory analysis of how varying tilt angles might influence spatial compatibility. However, we did not conduct this specific analysis in the current study, and as a result, the variation in tilt degrees introduced additional noise into our data.

## 5 Conclusion

In conclusion, the literature consistently demonstrates that misalignments with gravity, and general sensory mismatches affect fundamental sensory-motor skills required for piloting. Similarly, our study reveals a notable impact of body orientation and movement on manual precision during manual control, as well as post-choice confidence (see supplementary material section). Furthermore, we were able to show that spatial incompatibilities between body rotation and manual movement directions can further impact their control of the remotely controlled robot.

These findings not only contribute to our understanding of the intricate relationship between body dynamics and teleoperation but also pave the way for the development of safer teleoperation systems. By highlighting the potential negative impact of dynamic environments causing intersensory conflicts on teleoperation performance, our research emphasizes the need for further exploration in this domain. This underscores the importance of ongoing research in this area to improve the safety and effectiveness of teleoperation across various application domains.

## References

[1] Bashar I. Ahmad, Patrick M. Langdon, Simon J. Godsill, Robert Hardy, Lee Skrypchuk, and Richard Donkor. 2015. Touchscreen usability and input performance in vehicles under different road conditions: An evaluative study. In *Proceedings of the 7th International Conference on Automotive User Interfaces and Interactive Vehicular Applications*, 47–54.

[2] Airbus. 2024. Future Combat Air System (FCAS). Retrieved October 3, 2024 from https://www.airbus.com/en/products-services/defence/future-combat-air-system-fcas

[3] Hermann Aubert. 1861. Eine scheinbare bedeutende Drehung von Objecten bei Neigung des Kopfes nach rechts oder links. *Archiv für pathologische Anatomie und Physiologie und für klinische Medicin* 20, 3–4 (1861), 381–393.

[4] Airbus. 2024. Manned-Unmanned Teaming. Retrieved August 11, 2024 from https://www.airbus.com/en/products-services/defence/uas/manned-unmanned-teaming-mum-t

[5] J. Barra and D. Pérennou. 2013. Le sens de verticalité est-il vestibulaire? *Neurophysiologie Clinique/Clinical Neurophysiology* 43, 3 (June 2013), 197–204. DOI: https://doi.org/10.1016/j.neucli.2013.02.001

[6] Jules Bernard-Espina, Daniele Dal Canto, Mathieu Beraneck, Joseph McIntyre, and Michele Tagliabue. 2022. How tilting the head interferes with eye-hand coordination: The role of gravity in visuo-proprioceptive, cross-modal sensory transformations. *Frontiers in Integrative Neuroscience* 16 (2022), 788905. DOI: https://doi.org/10.3109/00016489709117982

[7] Naval Bhandari and Eamonn O'Neill. 2020. Influence of perspective on dynamic tasks in virtual reality. In *Proceedings of the 2020 IEEE Conference on Virtual Reality and 3D User Interfaces (VR)*. IEEE, 939–948.

[8] C. Bourdin, V. Nougier, L. Bringoux, G. M. Gauthier, P. A. Barraud, and C. Raphel. 2001. Accuracy level of pointing movements performed during slow passive whole-body rotations. *Experimental Brain Research* 138 (2001), 62–70. DOI: https://doi.org/10.1007/s002210000674

[9] Jean-Pierre Bresciani, Jean Blouin, K. Popov, Fabrice Sarlegna, Christophe Bourdin, Jean-Louis Vercher, and Gabriel Gauthier. 2002. Vestibular signal contributes to the online control of goal-directed arm movement. *Current Psychology of Cognition* 21 (Aug. 2002), 263–280.

[10] J. P. Bresciani, J. Blouin, K. Popov, C. Bourdin, F. Sarlegna, J. L. Vercher, and G. M. Gauthier. 2002. Galvanic vestibular stimulation in humans produces online arm movement deviations when reaching towards memorized visual targets. *Neuroscience Letters* 318, 1 (Jan. 2002), 34–38. DOI: https://doi.org/10.1016/S0304-3940(01)02462-4

[11] Jean-Pierre Bresciani, Gabriel M. Gauthier, Jean-Louis Vercher, and Jean Blouin. 2005. On the nature of the vestibular control of arm-reaching movements during whole-body rotations. *Experimental Brain Research* 164, 4 (Aug. 2005), 431–441. DOI: https://doi.org/10.1007/s00221-005-2263-4

[12] Joanna L. Brooks, Sergio Della Sala, and Stephen Darling. 2014. Representational pseudoneglect: A review. *Neuropsychology Review* 24, 2 (June 2014), 148–165. DOI: https://doi.org/10.1007/s11065-013-9245-2
[13] D. H. F. Chang, L. R. Harris, and N. F. Troje. 2010. Frames of reference for biological motion and face perception. *Journal of Vision* 10, 6 (June 2010), 22–22. DOI: https://doi.org/10.1167/10.6.22

[14] Mark Colley, Pascal Jansen, Enrico Rukzio, and JanGugenheimer. 2021. SwiVR-Car-Seat: Exploring vehicle motion effects on interaction quality in virtual reality automated driving using a motorized swivel seat. *Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies* 5, 4 (2021), 1–26.

[15] Alexandra Covaci, Anne-Hélène Olivier, and Franck Multon. 2015. Visual perspective and feedback guidance for VR free-throw training. *IEEE Computer Graphics and Applications* 35, 5 (2015), 55–65.

[16] Frédéric Crevecoeur, Joseph McIntyre, J.-L. Thonnard, and Philippe Lefèvre. 2010. Movement stability under uncertain internal models of dynamics. *Journal of Neurophysiology* 104, 3 (2010), 1301–1313. DOI: https://doi.org/10.1152/jn.00315.2010

[17] Frédéric Crevecoeur, Jean-Louis Thonnard, and Philippe Lefèvre. 2009. Forward models of inertial loads in weight-lessness. *Neuroscience* 161, 2 (2009), 589–598. DOI: https://doi.org/10.1016/j.neuroscience.2009.03.025

[18] Jan Drugowitsch, Gregory C. DeAngelis, Eliana M. Klier, Dora E. Angelaki, and Alexandre Pouget. 2014. Optimal multisensory decision-making in a reaction-time task. *eLife* 3 (June 2014), e03005. DOI: https://doi.org/10.7554/eLife.03005

[19] Richard T. Dyde, Michael R. Jenkin, and Laurence R. Harris. 2006. The subjective visual vertical and the perceptual upright. *Experimental Brain Research* 173, 4 (Aug. 2006), 612–622. DOI: https://doi.org/10.1007/s00221-006-0405-y

[20] Barbara A. Eriksen and Charles W. Eriksen. 1974. Effects of noise letters upon the identification of a target letter in a nonsearch task. *Perception & Psychophysics* 16, 1 (1974), 143–149.

[21] Marc O. Ernst and Heinrich H. Bülthoff. 2004. Merging the senses into a robust percept. *Trends in Cognitive Sciences* 8, 4 (2004), 162–169.

[22] Paul M. Fitts and Charles M. Seeger. 1953. SR compatibility: Spatial characteristics of stimulus and response codes. *Journal of Experimental Psychology* 46, 3 (1953), 199.

[23] C. Fossataro, A. Rossi Sebastiano, G. Tieri, K. Poles, M. Galigani, M. Pyasik, V. Bruno, T. Bertoni, and F. Garbarini. 2020. Immersive virtual reality reveals that visuo-proprioceptive discrepancy enlarges the hand-centred peripersonal space. *Neuropsychologia* 146 (Sept. 2020), 107540. DOI: https://doi.org/10.1016/j.neuropsychologia.2020.107540

[24] Florent Fouque, Benoit G. Bardy, Thomas A. Stoffregen, and Reinoud J. Bootsma. 1999. Action and intermodal information influence the perception of orientation. *Ecological Psychology* 11, 1 (1999), 1–43. DOI: https://doi.org/10.1207/s15326969eco1101_1

[25] Lindsey E. Fraser, Bobbak Makooie, and Laurence R. Harris. 2015. The subjective visual vertical and the subjective haptic vertical access different gravity estimates. *PLoS One* 10, 12 (Dec. 2015), e0145528. DOI: https://doi.org/10.1371/journal.pone.0145528

[26] Maria Gallagher, Breanne Kearney, and Elisa Raffaella Ferrè. 2021. Where is my hand in space? The internal model of gravity influences proprioception. *Biology Letters* 17, 6 (2021), 20210115. DOI: https://doi.org/10.1098/rsbl.2021.0115

[27] Geoffrey Gorisse, Olivier Christmann, Etienne Armand Amato, and Simon Richir. 2017. First-and third-person perspectives in immersive virtual environments: Presence and performance analysis of embodied users. *Frontiers in Robotics and AI* 4 (2017), 33.

[28] Bernhard Hommel. 2011. The Simon effect as tool and heuristic. *Acta Psychologica* 136, 2 (2011), 189–202.

[29] John J.-J. Kim, Meaghan E. McManus, and Laurence R. Harris. 2022. Body orientation affects the perceived size of objects. *Perception* 51, 1 (Jan. 2022), 25–36. DOI: https://doi.org/10.1177/03010066211065673

[30] Sabina Kleitman and Lazar Stankov. 2007. Self-confidence and metacognitive processes. *Learning and Individual Differences* 17, 2 (2007), 161–173.

[31] Wilfried Kunde, Jochen Müsseler, and Herbert Heuer. 2007. Spatial compatibility effects with tool use. *Human Factors* 49, 4 (2007), 661–670.

[32] Barbara La Scaleia, Francesco Lacquaniti, and Myrka Zago. 2019. Body orientation contributes to modelling the effects of gravity for target interception in humans. *The Journal of Physiology* 597, 7 (2019), 2021–2043. DOI: https://doi.org/10.1113/JP277469

[33] Skye Lee Pazuchanics. 2006. The effects of camera perspective and field of view on performance in teleoperated navigation. *Proceedings of the Human Factors and Ergonomics Society Annual Meeting* 50, 16 (Oct. 2006), 1528–1532. DOI: https://doi.org/10.1177/154193120605001603

[34] Mark Lipshits, Ana Bengoetxea, Guy Cheron, and Joseph McIntyre. 2005. Two reference frames for visual perception in two gravity conditions. *Perception* 34, 5 (May 2005), 545–555. DOI: https://doi.org/10.1068/p5358

[35] Marion Luyat and Edouard Gentaz. 2002. Body tilt effect on the reproduction of orientations: Studies on the visual oblique effect and subjective orientations. *Journal of Experimental Psychology: Human Perception and Performance* 28 (Sept. 2002), 1002–1011. DOI: https://doi.org/10.1037/0096-1523.28.4.1002
[36] Fred W. Mast, Giorgio Ganis, Stella Christie, and Stephen M. Kosslyn. 2003. Four types of visual mental imagery processing in upright and tilted observers. *Cognitive Brain Research* 17, 2 (July 2003), 238–247. DOI: https://doi.org/10.1016/S0926-6410(03)00111-3

[37] Kaleb McDowell, Kelvin S. Oie, Terrance M. Tierney, and Oded M. Flascher. 2007. Addressing human factors issues for future manned ground vehicles (MGVs). *Army Acquisition, Logistics and Technology Magazine* Jan.–Mar. (2007), 20–23.

[38] Joseph McIntyre, Myrka Zago, Alain Berthoz, and Francesco Lacquaniti. 2001. Does the brain model Newton's laws? *Nature Neuroscience* 4, 7 (2001), 693–694. DOI: https://doi.org/10.1038/89477

[39] Meaghan McManus and Laurence R. Harris. 2021. When gravity is not where it should be: How perceived orientation affects visual self-motion processing. *PLoS One* 16, 1 (2021), e0243381. DOI: https://doi.org/10.1371/journal.pone.0243381

[40] B. S. Mesland, A. L. Finlay, A. H. Wertheim, G. R. Barnes, A. B. Morland, A. M. Bronstein, and M. A. Gresty. 1996. Object motion perception during ego-motion: Patients with a complete loss of vestibular function vs. normals. *Brain Research Bulletin* 40, 5 (Jan. 1996), 459–465. DOI: https://doi.org/10.1016/0361-9230(96)00142-6

[41] Horst Mittelstaedt. 1983. A new solution to the problem of the subjective vertical. *Naturwissenschaften* 70, 6 (June 1983), 272–281. DOI: https://doi.org/10.1007/BF00404833

[42] Takuma Miwa, Rumi Hisakata, and Hirohiko Kaneko. 2019. Effects of the gravity direction in the environment and the visual polarity and body direction on the perception of object motion. *Vision Research* 164 (Nov. 2019), 12–23. DOI: https://doi.org/10.1016/j.visres.2019.08.005

[43] M. D. Moniruzzaman, Alexander Rassau, Douglas Chai, and Syed Mohammed Shamsul Islam. 2022. Teleoperation methods and enhancement techniques for mobile robots: A comprehensive survey. *Robotics and Autonomous Systems* 150 (2022), 103973.

[44] Georg Elias Müller. 1916. Über das Aubertsche Phänomen (About the Aubert phenomenon). *Z. Sinnesphysiol* 49 (1916), 109–246.

[45] Robin R. Murphy and Debra Schreckenghost. 2013. Survey of metrics for human-robot interaction. In *Proceedings of the 2013 8th ACM/IEEE International Conference on Human-Robot Interaction (HRI)*. IEEE, 197–198.

[46] Jochen Müsseler, Wilfried Kunde, Detlef Gausepohl, and Herbert Heuer. 2008. Does a tool eliminate spatial compatibility effects? *European Journal of Cognitive Psychology* 20, 2 (2008), 211–231.

[47] Robert W. Proctor and Kim-Phuong L. Vu. 2016. Principles for designing interfaces compatible with human information processing. *International Journal of Human-Computer Interaction* 32, 1 (2016), 2–22.

[48] Patrick Salamin, Daniel Thalmann, and Frédéric Vexo. 2006. The benefits of third-person perspective in virtual and augmented reality? In *Proceedings of the ACM Symposium on Virtual Reality Software and Technology*. ACM, 27–30. DOI: https://doi.org/10.1145/1180495.1180502

[49] Jeanine R. Schuler, Christopher J. Bockisch, Dominik Straumann, and Alexander A. Tarnutzer. 2010. Precision and accuracy of the subjective haptic vertical in the roll plane. *BMC Neuroscience* 11, 1 (July 2010), 83. DOI: https://doi.org/10.1186/1471-2202-11-83

[50] Cécile Scotto Di Cesare, Fabrice R. Sarlegna, Christophe Bourdin, Daniel R. Mestre, and Lionel Bringoux. 2014. Combined influence of visual scene and body tilt on arm pointing movements: Gravity matters! *PLoS One* 9, 6 (2014), e99866. DOI: https://doi.org/10.1371/journal.pone.0099866

[51] J. Richard Simon and John L. Craft. 1970. Effects of an irrelevant auditory stimulus on visual choice reaction time. *Journal of Experimental Psychology* 86, 2 (1970), 272. DOI: https://doi.org/10.1037/h0029961

[52] J. Richard Simon and Alan P. Rudell. 1967. Auditory S-R compatibility: The effect of an irrelevant cue on information processing. *Journal of Applied Psychology* 51 (1967), 300–304. DOI: https://doi.org/10.1037/h0020586

[53] J. Richard Simon and James D. Wolf. 1963. Choice reaction time as a function of angular stimulus-response correspondence and age. *Ergonomics* 6, 1 (1963), 99–105.

[54] B. N. Smetanin and K. E. Popov. 1997. Effect of body orientation with respect to gravity on directional accuracy of human pointing movements. *European Journal of Neuroscience* 9, 1 (1997), 7–11. DOI: https://doi.org/10.1111/j.1460-9568.1997.tb01347.x

[55] Charles Spence and Jon Driver. 2004. *Crossmodal Space and Crossmodal Attention*. Oxford University Press.

[56] Aaron Steinfeld, Terrence Fong, David Kaber, Michael Lewis, Jean Scholtz, Alan Schultz, and Michael Goodrich. 2006. Common metrics for human-robot interaction. In *Proceedings of the 1st ACM SIGCHI/SIGART Conference on Human-Robot Interaction*, 33–40.

[57] J. Ridley Stroop. 1935. Studies of interference in serial verbal reactions. *Journal of Experimental Psychology* 18, 6 (1935), 643.

[58] S. Tabak, H. Collewijn, and L. J. J. M. Boumans. 1997. Deviation of the subjective vertical in long-standing unilateral vestibular loss. *Acta Oto-Laryngologica* 117, 1 (Jan. 1997), 1–6. DOI: https://doi.org/10.3109/00016489709117982

[59] M. Tagliabue, L. Arnoux, and J. McIntyre. 2013. Keep your head on straight: Facilitating sensori-motor transformations for eye–hand coordination. *Neuroscience* 248 (2013), 88–94. DOI: https://doi.org/10.1016/j.neuroscience.2013.05.051
[60] Ryotaro Temma, Kazuki Takashima, Kazuyuki Fujita, Koh Sueda, and Yoshifumi Kitamura. 2019. Third-person piloting: Increasing situational awareness using a spatially coupled second drone. In *Proceedings of the 32nd Annual ACM Symposium on User Interface Software and Technology*. ACM, 507–519. DOI: https://doi.org/10.1145/3332165.3347953

[61] Yuki Ueyama and Masanori Harada. 2022. Effects of first-and third-person perspectives created using a head-mounted display on dart-throwing accuracy. *Virtual Reality* 26, 2 (2022), 687–695.