Effect of Physical and Virtual Feedback on Reach-to-Grasp Movements in Virtual Environments

Object grabbing is a common interaction task in virtual environments, where the virtual and physical feedback of both the hand and the targeted object may impact its performance. To investigate these effects, we first designed a comparative study where subjects were required to reach and grasp a physical cylinder under four conditions: 1) no virtual hand and no virtual cylinder; 2) virtual cylinder without virtual hand; 3) virtual hand and cylinder; and 4) real environment. The results showed that the subjects performed with different kinematic patterns in all three virtual conditions compared to the real environment. Additionally, we found that this difference is not due to the environment or depth illusion. We performed another experiment to examine the effects of physical cylinder feedback on reach-to-grasp movement. We found that the subjects performed similarly to the physical environment only in the condition with a virtual hand and a virtual cylinder. These results suggest that feedback with virtual hand and virtual targeted object would result in similar kinematic patterns in virtual environments as in physical environments, which implies design guidelines in virtual environments for rehabilitation in patients with motor deficits.