Size Perception Bias and Reach-to-Grasp Kinematics: An Exploratory Study on the Virtual Hand With a Consumer Immersive Virtual-Reality Device

Yoshihiro Itaguchi

doi:10.3389/frvir.2021.712378

Abstract

While studies have increasingly used virtual hands and objects in virtual environments to investigate various processes of psychological phenomena, conflicting findings have been reported even at the most basic level of perception and action. To reconcile this situation, the present study aimed 1) to assess biases in size perception of a virtual hand using a strict psychophysical method and 2) to provide firm and conclusive evidence of the kinematic characteristics of reach-to-grasp movements with various virtual effectors (whole hand or fingertips only, with or without tactile feedback of a target object). Experiments were conducted using a consumer immersive virtual reality device. In a size judgment task, participants judged whether a presented virtual hand or an everyday object was larger than the remembered size. The results showed the same amplitude of underestimation (approximately 5%) for the virtual hand and the object, and no influence of object location, visuo-proprioceptive congruency, or short-term experience of controlling the virtual hand. Furthermore, there was a moderate positive correlation between actual hand size and perception bias. Analyses of reach-to-grasp movements revealed longer movement times and larger maximum grip aperture (MGA) for a virtual, as opposed to a physical, environment, but the MGA did not change when grasping was performed without tactile feedback. The MGA appeared earlier in the time course of grasping movements in all virtual reality conditions, regardless of the type of virtual effector. These findings confirm and corroborate previous evidence and may contribute to the field of virtual hand interfaces for interactions with virtual worlds.

Highlights

An increasing number of studies use consumer immersive virtual reality (VR) devices to investigate human perception, cognition, and action (e.g., Keizer et al, 2016; Osumi et al, 2017; Freeman et al, 2018; Sawada et al, 2020)
The results show that the average point of subjective equality (PSE) in the hand size judgment was statistically smaller than 1 in all conditions, indicating that participants perceived the virtual hand to be smaller than their actual hand
The present study shows the same amplitude of underestimation of size perception for a virtual hand as for an everyday object in a virtual environments (VEs)

Summary

Introduction

An increasing number of studies use consumer immersive virtual reality (VR) devices to investigate human perception, cognition, and action (e.g., Keizer et al, 2016; Osumi et al, 2017; Freeman et al, 2018; Sawada et al, 2020). To accurately interpret cognitive or sensorimotor alterations in virtual environments (VEs), in psychological. Perception and Action in VR experiments as well as for practical applications, it is important to know the characteristics of perceptual and motor aspects of virtual objects and take those characteristics into consideration. Recent consumer VR devices have been shown to provide great accuracy even for experimental purposes (Hornsey et al, 2020), it has not yet been confirmed how the perception of the size of one’s own body parts differs between physical environments (PEs) and immersive VEs created by a current-generation consumer device (cf., Bhargava et al, 2021). To accurately interpret VR studies and improve VR experience, the characteristics of virtual hands in VEs in terms of both perception and motor control need to be elucidated

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Conclusion