Abstract
In the Rubber Hand Illusion, the feeling of ownership of a rubber hand displaced from a participant's real occluded hand is evoked by synchronously stroking both hands with paintbrushes. A change of perceived finger location towards the rubber hand (proprioceptive drift) has been reported to correlate with this illusion. To measure the time course of proprioceptive drift during the Rubber Hand Illusion, we regularly interrupted stroking (performed by robot arms) to measure perceived finger location. Measurements were made by projecting a probe dot into the field of view (using a semi-transparent mirror) and asking participants if the dot is to the left or to the right of their invisible hand (Experiment 1) or to adjust the position of the dot to that of their invisible hand (Experiment 2). We varied both the measurement frequency (every 10 s, 40 s, 120 s) and the mode of stroking (synchronous, asynchronous, just vision). Surprisingly, with frequent measurements, proprioceptive drift occurs not only in the synchronous stroking condition but also in the two control conditions (asynchronous stroking, just vision). Proprioceptive drift in the synchronous stroking condition is never higher than in the just vision condition. Only continuous exposure to asynchronous stroking prevents proprioceptive drift and thus replicates the differences in drift reported in the literature. By contrast, complementary subjective ratings (questionnaire) show that the feeling of ownership requires synchronous stroking and is not present in the asynchronous stroking condition. Thus, subjective ratings and drift are dissociated. We conclude that different mechanisms of multisensory integration are responsible for proprioceptive drift and the feeling of ownership. Proprioceptive drift relies on visuoproprioceptive integration alone, a process that is inhibited by asynchronous stroking, the most common control condition in Rubber Hand Illusion experiments. This dissociation implies that conclusions about feelings of ownership cannot be drawn from measuring proprioceptive drift alone.
Highlights
The Rubber Hand Illusion (RHI) is a tantalizing illusion, where the feeling that a rubber hand belongs to one’s body is brought about by stroking a visible rubber hand synchronously to the participant’s own occluded hand
Our findings show a dissociation of proprioceptive drift and the reported feeling of ownership and suggest that these two phenomena result from different processes of multisensory integration
The interruptions we introduced to measure the proprioceptive drift have the unexpected effect to interrupt the accumulation of evidence against the unity assumption
Summary
The Rubber Hand Illusion (RHI) is a tantalizing illusion, where the feeling that a rubber hand belongs to one’s body (feeling of ownership) is brought about by stroking a visible rubber hand synchronously to the participant’s own occluded hand. Participants rated the subjective experience to own the rubber hand high in a questionnaire if stroking was synchronous but not if stroking was asynchronous. In a second experiment, perceived position of the participant’s left index finger was measured by an inter-manual reaching task in darkness. A displacement of reaches towards the rubber hand occurred in the case of synchronous stimulation, but not in the case of asynchronous stimulation. This displacement effect has been referred to as proprioceptive drift (e.g., [2]). The magnitude of the proprioceptive drift correlated with the strength of the feeling of ownership reported in the questionnaire
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
