Title
The Supernumerary hand illusion in augmented reality
Author
Rosa, N.
Veltkamp, R.C.
Hurst, W.
Nijboer, T.
Gilbers, C.
Werkhoven, P.
Publication year
2019
Abstract
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 virtual reality. In augmented reality (AR), however, visually present real limbs can be augmented with (multiple) fake virtual limbs, which results in a variation of the RHI, the augmented reality supernumerary hand illusion (ARSHI). Such conditions occur, for example, in frst-person AR games and in AR-interfaces for tele-robotics. In this article, we examined to what extent humans can experience the sense of embodiment over a supernumerary virtual arm in addition to one or two real arms. We also examine how embodiment is a?ected by the perceptual visual-tactile synchronicity of the virtual and real limbs, and by the synchronicity of active movement of the virtual and real hand. Embodiment was measured subjectively by questionnaire and objectively by skin conductance responses (SCRs). Questionnaire responses show that ownership, agency, and self-location can be evoked over the virtual arm in the presence of a real arm, and that they are signifcantly stronger for synchronous conditions than for asynchronous conditions. The perceptual and motorical synchronous condition with three visible hands led to an experience of owning the virtual hand. These responses further show that agency was also strongly experienced over the supernumerary virtual arm, and responses regarding self-location suggest a shift in sensed location when one real arm was in view and an additional location when both real arms where in view. SCRs show no signifcant e?ect of condition, but do show a signifcant habituation e?ect as a function of the number of conditions performed by participants. When analyzing the relations at the individual participant level between the questionnaire data and skin conductance, we found two clusters of participants: (1) participants with low questionnaire responses and low-medium SCRs and (2) participants with high questionnaire responses and low-high SCRs. Finally, we discuss how virtual hand appearance/realism and willingness to accept virtual limbs could play an important role in the ARSHI, and provide insights on intricacies involved with measuring and evaluating RHIs. © 2019 Association for Computing Machinery.
Subject
Agency
Augmented reality
Multisensory
Ownership
Rubber hand illusion
Self-location
Sense of embodiment
Skin conductance habituation
Supernumerary hand illusion
Virtual hand illusion
Augmented reality
Location
Rubber
Multisensory
Virtual hand
Virtual reality
To reference this document use:
http://resolver.tudelft.nl/uuid:91670180-c57f-47ba-ac0e-6c7fe7a92dfd
TNO identifier
869620
Publisher
Association for Computing Machinery
ISSN
1544-3558
Source
ACM Transactions on Applied Perception, 16 (2)
Article number
12
Document type
article