Embodiment in a virtual body that speaks produces agency over the speaking but does not necessarily influence subsequent real speaking

Abstract

Previous results have shown that body ownership, induced through first-person perspective (1PP) over a virtual body (VB) that moves synchronously with real body movements, can lead to illusory agency over VB utterances even though the participant does not speak. It was also found that when participants later speak they follow the fundamental frequency (FF) of the voice of their VB, indicating a new motor plan for speaking. To eliminate the contribution of veridical agency over the VB movements, we conducted a study where we induced body ownership using visuotactile (VT) synchrony rather than visuomotor. Participants saw a life-sized VB from 1PP and reflected in a virtual mirror, that spoke with corresponding lip movements. Half of the 36 experimental participants experienced synchronous (Sync) passive VT on their hands and abdomen, and the other half asynchronous (Async). We found that both VT Sync and Async conditions resulted in a strong subjective illusion of body ownership and agency over the VB, but not, however, changes in voice FF in subsequent speaking. This shows that although illusory agency may be associated with body ownership, a change in motor plan is likely to be a generalisation from veridical agency over whole body movements.