What's limbs got to do with it? Real-world movement correlates with feelings of ownership over virtual arms during object interactions in virtual reality.

Humans will initially move awkwardly so that the end-state of their movement is comfortable. But, what is comfortable? We might assume it refers to a particular physical body posture, however, humans have been shown to move a computer cursor on a screen with an out-of-sight hand less efficiently (curved) such that the visual representation more efficient (straight). This suggests that movement plans are made in large part to satisfy the demands of their visual appearance, rather than their physical movement properties. So, what determines if a body movement is comfortable-how it feels or how it looks? We translated an object-interaction task from the real-world into immersive virtual reality (IVR) to dissociate a movement from its visual appearance. Participants completed at least 20 trials in two conditions: Controllers-where participants saw a visual representation of the hand-held controllers and Arms-where they saw a set of virtual limbs. We found participants seeing virtual limbs moved in a less biomechanically efficient manner to make the limbs similar to if they were interacting with a real-world object. These movement changes correlated with an increase in self-reported feelings of ownership over the limbs as compared to the controllers. Overall this suggests we plan our movements to provide optimal visual feedback, even at the cost of being less efficient. Moreover, we speculate that a detailed measurement of how people move in IVR may provide a new tool for assessing their degree of embodiment. There is something about seeing a set of limbs in front of you, doing your actions, that affects your moving, and in essence, your thinking.