Abstract
We feel as if we exist in a virtual reality (VR) world especially when our actions
are directly projected on a Computer Graphics (CG) character in the VR world. Such
feelings are said to be achieved by a sense of ownership for the CG characters. Previous
research suggests that the synchronicity between somatosensory input and visual
information are crucial to attain this sense of ownership. Although several studies
have investigated the temporal synchronizations between actual and virtual actions, no
study has assessed how the discrepancies in the correspondence between these actions
affect the emergence of a sense of ownership. In the present study, we employed a
“rock-paper-scissors” game task in a VR world in which the players’ actions (i.e., rock,
paper, or scissors) were projected onto the actions of a CG character with zero (0%),
low (33%), moderate (66%), or total (100%) correspondences. Total correspondence
indicated complete synchronization between the actions of the player and the CG character,
i.e., when the player produced one of the three actions (rock, paper, or scissors),
the CG character produced the same action. In the zero correspondence condition,
their actions did not coincide, i.e., when the player produced one of the three actions,
the CG character strictly produced different actions. The results showed that a sense of
agency in terms of the subjective reports increased as a function of the correspondences
between the player’s and CG character’s actions. As a probe test, after each 100 trial,
games of a correspondence condition were introduced, in which the CG character’s
arm was suddenly almost cut by a Japanese sword. A survey after completion of the
task revealed that the sense of agency increased as a function of the correspondences.
This suggested that the synchronizations of the actions are crucial for attaining a sense
of ownership, as well as increase the sense of agency. In contrast, the systolic blood
pressure increased only after the total correspondence condition, and was higher than
those observed in the other three correspondence conditions, suggesting that any subtle
decrement in correspondence does not produce a sense of ownership, as assessed by the
physiological indicator. In other words, there was a discrepancy between the psychological
and physiological sense of ownership at the moderate contingency condition. A
temporal de-synchronization may produce a sense of ownership; however, any decrement
in the correspondence between actual and virtual actions is insufficient to evoke
a sense of ownership.
