自我表征的可塑性:基于橡胶手错觉的研究

自我识别是人类自我觉知的行为标记。传统方法认为稳定的自我表征是自我识别的基础。随着对橡胶手错觉及一系列自我表征和自我识别错觉的揭示,这一能让人将外部客体感知为自身一部分的错觉研究使得我们能够以多感官整合的方式来研究自我表征和自我识别。拥有感和自主感被认为是我们进行自我识别的两类基本体验,本文对一系列橡胶手错觉范式研究的系统回顾表明,拥有感和自主感会发生改变,这说明人的自我表征是可变的和可塑的。

The Plasticity of Self-Representation: Based on the Studies of Rubber Hand Illusion

Self-recognition is considered as the behavioral marker of self-awareness, because previous studies showed only a small selection of primate species possess the ability to recognize their own physical features in a mirror. Self-recognition is fixed as traditional unimodal methods such as self-other detection tasks, self-other morphing tasks or masked priming tasks suggested. The arising of rubber hand illusion not only changes the study of self-recognition methodologically, but also suggests that self-representations are malleable, thus self-recognition should be plastic accordingly. Rubber hand illusion is the experience of an artificial body part as becoming a real body part. A rubber hand was placed in front of participants whose corresponding real hand was hidden from sight. Participants reported to experience the rubber hand as their own body part after the real hand and the visible rubber hand were stroked synchronously for 10 minutes. With various minor or major variations, this illusion is widely used to induce illusions of sense of ownership and sense of ownership, which are considered as two basic experiences to help us recognize ourselves. This paradigm makes it possible to investigate the intimate relations among sense of ownership, sense of agency, self-representation, self-recognition, and different kinds of illusions.Converging evidence for temporal consistency, spatial consistency and feature consistency as three main factors that may affect the ownership illusion was found. Except for temporal rule, the exact roles of the other two factors are not entirely clear. Other studies did not find an effect of distance or object. The same situation exists in the studies of sense of agency. The importance of the congruency between real action and its feedback was proved by numerous studies, but there were still some studies showed participants could perceive agency even in cases of rather large spatiotemporal discrepancies. However, it is non-controversial that the setups of rubber hand illusion can influence people’s sense of agency and sense of ownership, and so do “enfacement illusion”, “the whole body illusion”, as well as “rubber voice illusion” which can affect participants’ sense of face ownership, sense of whole body ownership, and sense of voice ownership respectively. In the present paper, we reviewed a series of studies focusing on sense of ownership, sense of agency, as well as self-recognition. These multimodal studies gave enough evidence for one hypothesis that self-representation is plastic, which might be explained by the free-energy principle. According to this principle, the brain always attempts to minimize the amount of surprise, for which it may need to update probabilistic representations. In other words, when there is any new information which reveals a discrepancy between a predicated sensory sate and the actual sensory state, then probabilistic presentations of ourselves will be changed and updated, which means the representations of the self are malleable, therefore self-recognition should also be plastic. The free-energy principle gives an optional choice for the explaining of self-representation and self-recognition, but current evidence is not sufficient enough to deny the role of top-down body representation. Further investigations and improvement of the methodology itself are needed in order to test this hypothesis empirically.