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.
Highlights
People interact with physical objects in their surroundings by reach-to-grasp movements
The system we used could potentially emulate visuomotor interactions with objects within the computerized space, the results showed that grasping trajectories within this system were atypical; Just as in the case of interactions with 2D images of objects, grip apertures obeyed to Weber’s law
A repeated-measures ANOVA with block (3 levels), normalized movement time (10 levels), and object size (15, 25, 35, 45 cm) as within-subject independent variables was conducted on the grip aperture data
Summary
People interact with physical objects in their surroundings by reach-to-grasp movements. When grasping movements are directed to 2D targets, grasping apertures show an abnormal pattern of adherence to Weber’s law (Holmes and Heath, 2013; Hosang et al, 2016; Ozana and Ganel, 2019a; Ozana et al, 2020) These findings, again, suggest that visuomotor interactions with virtual objects are subjected to perceptual and relative heuristics. The pattern of adherence to Weber’s law in the haptic feedback condition was similar to that obtained in a matched no-feedback condition These findings converge with previous results (Afgin et al, 2017), to suggest that visuomotor control in virtual environments relies on less efficient, relative computations of size. Could grasping in a 3D VR environment escape the influence of Weber’s law? What contribution does haptic feedback have to grasping performance within VR?
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