Resisting the Avatar: Motor Responses to Spatial Distortions in Upper- and Lower-Limb Reaching Without Visual Targets.

Avatars can serve as virtual representations of a user's body, replicating their movements in real time within an immersive environment. When these movements are closely synchronized with those of the user, a sense of embodiment over the avatar is often experienced. Recent research shows that introducing spatial offsets between a user's real movements and those of their avatar can alter motor behavior, with users aligning with the distorted avatar. While previous studies have typically focused on upper-limb movements toward visual targets, it remains unclear how users respond to distortions without such targets, particularly during lower-limb tasks where postural demands may impose constraints. This study examined whether users adjust their movements to follow their distorted avatar during upper- and lower-limb reaching without visual targets. Twenty-four participants performed reaching tasks while their avatar's movements were spatially offset. Results revealed that participants counteracted the avatar's distortion by moving in the opposite direction in both limb tasks. These findings suggest that, in the absence of explicit visual targets, participants treat spatial distortions as execution errors and prioritize internal movement goals over minimizing sensory conflict. This suggests that adaptation depends not only on a strong embodiment but also on whether the task performance permits reducing the mismatch between the user's and the avatar's movements.