Temporal Availability of Ebbinghaus Illusions on Perceiving and Interacting with 3D Objects in a Contextual Virtual Environment

Contextual illusions, such as the Ebbinghaus Illusion, can be potentially used to improve or hinder reach-to-grasp interaction in a virtual environment by affecting the perception of object size and the action. However, the illusion effect has only been evaluated using 2D objects like discs or annuluses, and limited research has been conducted in a virtual environment. Moreover, it remains unknown how the sudden, or dynamic, change of surrounding features will impact the perception and then the action towards the object. In this paper, we conducted a series of experiments to evaluate the effects of 3D Ebbinghaus illusion with dynamic surrounding features on the task of reaching to grasp a 3D object in an immersive virtual environment. An innovative 3D perceptual judgment task revealed that the static 3D illusion affected the perceived size of the 3D object. Then, we experimentally manipulated the visual gain and loss of the 3D contextual inducers, the participant's virtual hand, and the entire 3D contextual object. Results revealed that the depth error (error in depth of reaching action) was influenced by a dynamic change in the size of the inducers, the fine adjustment of grasp was dependent on the visual presence of the virtual hand and vision of 3D contextual object was required for the reaching and grasping movements. These results will benefit the understanding of reach-to-grasp interactions in immersive virtual environments and can improve interaction design.