Abstract
Virtual-hand-illusion studies often use explicit and implicit measures of body ownership but no agreed-on implicit measure of agency exists. We investigated whether the Intentional Binding (IB) effect could serve as such a measure. A pilot study confirmed that current consistency increases both perceived agency and IB. In three experiments, current consistency was 50% but the previously experienced consistency was either 100% or 0%. When previous and present consistency experience were separated by a short break, both explicit judgments and IB showed a contrast effect. Eliminating the break reversed the effect in explicit agency but not in IB; and making the transition between previous and present consistency smoother replicated the effect for explicit agency but reversed the pattern for IB. Our findings suggest that explicit agency and IB rely on different sources of information, presumably including cross-sensory correlations, predictions of expected action-effects, and comparisons between present and previous consistency experiences.
Highlights
Our body may be the object we know the best, as it is through the body that we interact with the outside world and experience it by generating exteroceptive and interoceptive sensory information
The pilot study confirmed that our experimental setup is suitable to evoke standard virtual hand illusion (VHI) effects and intentional binding (IB) effects in both explicit and implicit measures of agency
Our findings fit with the assumption that perceived agency is not a direct function of particular consistency parameters or values but rather emerges from an interaction between these parameters and particular expectations: If participants expect a total lack of control over the virtual hand, as after previous inconsistency, medium control is perceived as an indicator of substantially more control but if they expect complete control, as after previous consistency, medium control rather seems to indicate little control
Summary
Our body may be the object we know the best, as it is through the body that we interact with the outside world and experience it by generating exteroceptive and interoceptive sensory information. While some studies using the RHI have gathered evidence that explicit judgments of body ownership are unrelated to explicit judgments of agency[3,4], some other studies using a variant of the RHI task that allows for voluntary action of the participant point to a rather tight relationship between body ownership and agency In this variant, the rubber hand is replaced by a virtual hand, presented in virtual reality environment, which the participant can operate synchronously or asynchronously by means of a data glove[5]. In the VHI paradigm, a very tight relationship (i.e., strong correlations) between perceived ownership and agency judgments can be observed[7] This is likely to do with the fact that the virtual-hand design provides much more, and much more ecologically valid information than the rubber-hand design[8]: Feeling one’s own movement while seeing a virtual hand moving for a couple of seconds generates thousands of data points to compute visuomotor correlations. The assumption is the same: the causality between action and tone creates the illusion that they occur closer in time
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