Research On The Moving Hand Illusion And It's Formation Mechanism

Body awareness depends on two basic ingredients: experiencing limbs as part of one‘s own body—the sense of body ownership and experiencing oneself in voluntary control of one‘s bodily actions—the sense of agency. Body ownership is the experience that ??my body‘‘ belongs to me, and it is the source of sensations which is unique to myself. As afferent component, peripheral signals from different sensory modalities indicate the state of ?my body?. Agency refers to the sense that I am the author of actions. I can control not only my body movements but also the external events via my actions. As efferent component, motor commands precede voluntary action. It‘s worth noting that not only voluntary actions but also passive experience can evoke the sense of body ownership. However, sense of agency arises only when the one is at active state. This indicates that they have different effects on body awareness. Studies indicate that these two ingredients interact in producing ownership illusions. However, the interaction between them is still confusing: Some studies reported a positive correlation between ownership and agency, some studies obtained the opposite result, and even a few studies found no correlation. Therefore, we explored how the sense of agency interacts with the sense of ownership, and how the personal characteristic influence the moving hand illusion through 3 studies including 7 experiments. We added imitation factor into the experiments, referencing to the classic multisensory stimulation paradigm. The results of the experiments are as follow:Study1: In experiment 1, the synchronization of imitation can induce moving hand illusion; respect to the synchronous tactile stimuli condition, synchronous imitation, participants established stronger sense of agency and ownership over the hand of others. In experiment 2, relative to asynchronous imitate situation, threat stimulus evoked more galvanic skin response in synchronous imitation.Study 2: In the experiment 3, when the angles between the two hands were at 60 degrees, the participant perceived higher agency and ownership of the hand of others hand in imitation condition than tactile condition. In experiment 4, participants experienced stronger illusion in active condition than passive condition. In experiment 5,synchronous imitation induced moving hand illusion; fisting imitation induce stronger illusion experience than lifting finger imitation; participants perceived higher agency and ownership over the hand of others hand when the angles were at 0 degrees than at 60 degrees. In experiment 6, ipsilateral imitation evoked stronger illusion experience than contralateral imitation.Study 3: We investigated how personal factors influence the moving hand illusion in experiment 7. The results show that there is negative correlation between the illusion and empathy concern, negative correlation between the illusion and verbal-imagery, positive correlation between the illusion and internality. Considering the above results, we can conclude that:(a) synchronous imitation can induce the moving hand illusion, and the illusion might be based on not only bottom-up but also top-down processes;(b) there is positive correlation between sense of agency and sense of ownership and agency could improve ownership;(c) personal factors, such as empathy, cognitive style and internality, are important reasons for the illusion experience differences between subjects.