Brain, Body and Self Laboratory, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
PLoS One. 2011 Feb 23;6(2):e17208. doi: 10.1371/journal.pone.0017208.
Could it be possible that, in the not-so-distant future, we will be able to reshape the human body so as to have extra limbs? A third arm helping us out with the weekly shopping in the local grocery store, or an extra artificial limb assisting a paralysed person? Here we report a perceptual illusion in which a rubber right hand, placed beside the real hand in full view of the participant, is perceived as a supernumerary limb belonging to the participant's own body. This effect was supported by questionnaire data in conjunction with physiological evidence obtained from skin conductance responses when physically threatening either the rubber hand or the real one. In four well-controlled experiments, we demonstrate the minimal required conditions for the elicitation of this "supernumerary hand illusion". In the fifth, and final experiment, we show that the illusion reported here is qualitatively different from the traditional rubber hand illusion as it is characterised by less disownership of the real hand and a stronger feeling of having two right hands. These results suggest that the artificial hand 'borrows' some of the multisensory processes that represent the real hand, leading to duplication of touch and ownership of two right arms. This work represents a major advance because it challenges the traditional view of the gross morphology of the human body as a fundamental constraint on what we can come to experience as our physical self, by showing that the body representation can easily be updated to incorporate an additional limb.
在不太遥远的未来，我们是否能够重塑人体，从而拥有额外的肢体？一只额外的手臂帮助我们在当地杂货店每周购物，或者一个额外的假肢帮助瘫痪的人？在这里，我们报告了一种知觉错觉，即在参与者的全视野中，将一只橡胶右手放在真实的手旁边，参与者会将其视为属于自己身体的额外肢体。问卷调查数据以及当身体威胁橡胶手或真实手时获得的皮肤电反应的生理证据支持了这一效应。在四个精心控制的实验中，我们展示了引发这种“额外手错觉”所需的最小条件。在第五个也是最后一个实验中，我们表明，这里报告的错觉与传统的橡胶手错觉不同，因为它的特点是对真实手的自我否定感较弱，而对拥有两只右手的感觉更强。这些结果表明，人工手“借用”了一些代表真实手的多感觉过程，导致触觉和对两只右手的所有权的重复。这项工作是一项重大进展，因为它通过表明身体的表现可以很容易地更新以包含额外的肢体，从而挑战了人体总体形态作为我们所能体验到的身体自我的基本限制的传统观点。
