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

Area of Science:

• Human-computer interaction
• Virtual reality
• Motor control

Background:

• Avatars in immersive environments can create a sense of embodiment when synchronized with user movements.
• Spatial offsets between user and avatar movements can alter motor behavior, typically leading to user alignment with the avatar.
• Previous research focused on upper-limb movements towards targets, leaving lower-limb responses and targetless scenarios unexplored.

Purpose of the Study:

• To investigate if users adjust their movements to align with a spatially distorted avatar during upper- and lower-limb reaching tasks without visual targets.
• To determine how postural demands in lower-limb tasks influence responses to avatar distortions.
• To understand the role of internal movement goals versus sensory conflict minimization in adaptation.

Main Methods:

• Twenty-four participants performed reaching tasks in a virtual environment.
• Avatar movements were spatially offset from the participants' real movements.
• Both upper-limb and lower-limb movements were assessed in the absence of visual targets.

Main Results:

• Participants consistently moved in the opposite direction of the avatar's spatial distortion for both upper- and lower-limb tasks.
• This counteraction occurred despite the presence of embodiment, indicating a different adaptation strategy.
• The findings suggest a prioritization of internal movement goals over reducing sensory conflict.

Conclusions:

• In targetless reaching tasks, users counteract avatar spatial distortions, treating them as execution errors.
• Adaptation to avatar distortions is influenced by the degree of embodiment and the task's ability to resolve sensory-motor mismatches.
• Internal movement representations play a crucial role in motor behavior within virtual environments.