Grasping Weber’s Law in a Virtual Environment: The Effect of Haptic Feedback

Abstract

Recent findings suggest that the functional separation between vision-for-action and vision-for-perception does not generalize to situations in which virtual objects are used as targets. For instance, unlike actions toward real objects that violate Weber's law, a basic law of visual perception, actions toward virtual objects presented on flat-screens, or in remote virtual environments, obey to Weber's law. These results suggest that actions in virtual environments are performed in an inefficient manner and are subjected to perceptual effects. It is unclear, however, whether this inefficiency reflects extensive variation in the way in which visual information is processed in virtual environments or more local aspects related to the settings of the virtual environment. In the current study, we focused on grasping performance in a state-of-the-art virtual reality system that provides an accurate representation of the 3D space. Within this environment, we tested the effect of haptic feedback on grasping trajectories. Participants were asked to perform bimanual grasping movements toward the edges of virtual targets. In the haptic feedback condition, physical stimuli of matching dimensions were embedded in the virtual environment. Haptic feedback was not provided in the no-feedback condition. The results showed that grasping trajectories in the feedback, but not in the no-feedback condition, could be performed more efficiently, and evade the influence of Weber's law. These findings are discussed in relevance to previous literature on 2D and 3D grasping.

Familiar size affects perception differently in virtual reality and the real world

“…Researchers take different theoretical perspectives about the degree to which VR can serve as a proxy for reality [103] or not [5]. This debate has often centred on the use of VR to study vision for action, where 3D vision and realness may be particularly important [104][105][106]. However, even our purely perceptual task reveals substantial differences.…”

Grasping follows Weber's law: How to use response variability as a proxy for JND

“…Typically, the idea was to learn something about the mechanisms that cause the presumed violation of Weber's law. These studies investigated, for example, whether grasping adhered to Weber's law when the object is shown only in 2D ( Hosang et al., 2016 ), when the object is distorted by certain visual illusions which selectively distort the size of the object but not the positions of the grasp points on the object ( Smeets et al., 2020 ), in pantomimed grasping ( Jazi & Heath, 2016 ; Jazi & Heath, 2017 ; Jazi, Yau, Westwood, & Heath, 2015 ), when grasping 3D objects underneath a glass surface ( Ozana & Ganel, 2017 ), or when grasping with both hands in a virtual environment ( Ozana, Berman, & Ganel, 2020 ). Some studies ( Holmes et al., 2011 ) also looked at the time course and development of Weber's law over the entire grasping trajectory (but see Foster & Franz, 2013 ).…”

Visual processing of actions directed towards three-dimensional objects in immersive virtual reality may involve holistic processing of object shape

“…While this underperception of distance is reported as being less in newer displays compared to older displays, this issue suggests that the HMD-VR environment may be processed more as 2D compared to the real world (Kelly et al, 2017). A second is recent findings that grasping virtual 3D objects adheres to Weber's law, and is therefore susceptible to perceptual effects Ozana et al, 2020a). Taken together, these findings suggest that vision-for-action for grasping virtual 3D objects in HMD-VR may be processed more like 2D objects and importantly, that actions in HMD-VR may involve holistic processing and be susceptible to perceptual effects.…”