Hiding Assistive Robots During Training in Immersive VR Does Not Affect Users’ Motivation, Presence, Embodiment, Performance, Nor Visual Attention

Abstract

Combining immersive virtual reality (VR) using head-mounted displays (HMDs) with assisting robotic devices might be a promising procedure to enhance neurorehabilitation. However, it is still an open question how immersive virtual environments (VE) should be designed when interacting with rehabilitation robots. In conventional training, the robot is usually not visually represented in the VE, resulting in a visuo-haptic sensory conflict between what users see and feel. This study aimed to investigate how motivation, embodiment, and presence are affected by this visuo-haptic sensory conflict. Using an HMD and a rehabilitation robot, 28 healthy participants performed a path-tracing task, while the robot was either visually reproduced in the VE or not and while the robot either assisted the movements or not. Participants' performance and visual attention were measured during the tasks, and after each visibility/assistance condition, they reported their motivation, presence, and embodiment with questionnaires. We found that, independently of the assistance, the robot visibility did not affect participants' motivation, presence, embodiment, nor task performance. We only found a greater effort/importance reported when the robot was visible. The visual attention was also slightly affected by the robot's visibility. Importantly, we found that the robotic assistance hampered presence and embodiment, but improved motivation. Our results indicate no disadvantage of not reproducing robotic devices in VEs when using HMDs. However, caution must be put when developing assisting controllers, as they might hamper users' affect.

Naturalistic visualization of reaching movements using head-mounted displays improves movement quality compared to conventional computer screens and proves high usability

“…Another limitation, which affects only the experiment with brain-injured patients, might be the potential visuohaptic conflict between the haptic stimuli-due to the weight support applied by the assistive device-and the visual absence of the device in the VE, i.e., the exoskeleton was not visible in the VE. Although it is unknown how this sensory conflict might have affected the patients in their movement quality or motivation and cognitive load reporting, recent evidence suggests that not visualizing assistive devices during training in immersive VR does not affect the users' motivation, performance, nor visual attention, at least in a healthy young population [59].…”

Naturalistic visualization of reaching movements using head-mounted displays improves movement quality and proves high usability compared to conventional computer screens

“…Another limitation, which affects only the experiment with brain-injured patients, might be the potential visuohaptic conflict between the haptic stimulidue to the weight support applied by the assistive device -and the visual absence of the device in the VE, i.e., the exoskeleton was not visible in the VE. Although it is unknown how this sensory conflict might have affected the patients in their movement quality or motivation and cognitive load reporting, recent evidence suggests that do not visualizing assistive devices during training in immersive VR does not affect the users' motivation, performance, nor visual attention, at least in a healthy young population [56].…”

To Reach the Unreachable: Exploring the Potential of VR Hand Redirection for Upper Limb Rehabilitation

“…The sense of hand ownership can be measured by the noticeability of hand redirection. A reduced sense of hand ownership makes hand redirection more noticeable, which may negatively impact rehabilitation as it reminds patients that their good performance results from external help, thereby reducing their motivation [80]. As a result, it is crucial to find an optimal form of hand redirection that can facilitate improved performance in patients while maintaining a strong sense of hand ownership.…”