Visually-guided interceptive actions performed in virtual environments

Abstract

Virtual environments are quickly becoming a pervasive part of everyday life, yet little is known about the visuomotor control of actions performed in these conditions. This is particularly the case for interceptive actions, during which performers interact with objects that are seen, but in virtual environments, are not physically present. We hypothesized that the absence of a targeted object would lead to actions being more influenced by illusory context (and hence the result of different visuomotor processing) when compared to actions performed if the object were present. Twelve participants grasped objects of different lengths that were embedded in a control or illusory background (Ponzo illusion; see Ganel, Tanzer, & Goodale, 2008). Crucially, objects were viewed through a half-silvered mirror in two conditions that simulated (i) a natural environment where the objects sat on a surface in front of participants, and (ii) a virtual environment where the objects appeared to be in an identical position, but were actually images produced by the mirror. Optotrak cameras measured the grip aperture of participants. Results showed that, when grasping objects placed against the control background, there was no difference in the scaling of the actions performed in the natural and virtual environments (slope of object size vs. maximum grip aperture; t(11)=-.94, p=.37, two-tailed). In contrast, the illusory background altered the scaling of the grasping actions more in the virtual environment than it did for actions in the natural environment (normalized illusion effect; t(11)=1.92, p=.040, one-tailed). These results suggest that, when compared to natural actions, visually-guided interceptive actions performed in virtual environments are more sensitive to visual illusions. This is consistent with the idea that actions in virtual environments may rely on different (allocentric rather than egocentric) visuomotor processing, and raises doubt about the suitability of virtual environments for testing and training visually-guided actions. Meeting abstract presented at VSS 2014