Blaise Celia R, Clark Holly C, Saal Hannes P
Active Touch Laboratory, School of Psychology, University of Sheffield, Sheffield S1 4DP, UK.
School of History, Philosophy and Digital Humanities, University of Sheffield, Sheffield S1 4DT, UK.
Proc Biol Sci. 2025 Aug;292(2052):20251255. doi: 10.1098/rspb.2025.1255. Epub 2025 Aug 13.
Distinguishing our body from the external world is crucial for self-perception and environmental interaction. Yet, the accuracy with which we perceive this boundary remains underexplored. Here, we developed a psychophysical protocol to assess how accurately individuals perceive their body boundaries. Participants were asked whether the midpoint between two tactile stimuli was inside or outside their perceived body boundary. Three-dimensional scans provided objective anatomical boundaries, allowing psychometric functions to be fitted. Results revealed remarkable overall precision, often within millimetres, in localizing body boundaries across multiple body regions. However, accuracy varied: while palm boundaries were localized nearly perfectly, stimuli along the wrist boundaries were frequently misjudged as extending beyond their true anatomical limit, revealing a systematic perceptual bias. Perceptual judgements adapted to changes in posture, but accuracy declined when the detailed local three-dimensional structure was omitted, indicating that proprioceptive cues are combined with detailed local body models. Finally, participants whose anatomy deviated from the average tended to align their responses with a typical body model rather than their unique physiology, suggesting that top-down processes influence boundary judgements. Our findings suggest that body boundary representation combines detailed three-dimensional body models with proprioceptive feedback into an integrated perceptual model of the anatomical body.
区分我们的身体与外部世界对于自我认知和与环境的互动至关重要。然而，我们感知这一边界的准确性仍未得到充分探索。在这里，我们开发了一种心理物理学方法来评估个体对其身体边界的感知有多准确。参与者被问及两个触觉刺激之间的中点是在他们所感知的身体边界之内还是之外。三维扫描提供了客观的解剖学边界，从而能够拟合心理测量函数。结果显示，在定位多个身体部位的身体边界时，总体精度非常高，通常在几毫米之内。然而，准确性存在差异：手掌边界的定位几乎完美，而沿着手腕边界的刺激经常被误判为超出其真实解剖学界限，这揭示了一种系统性的感知偏差。感知判断会适应姿势的变化，但当省略详细的局部三维结构时，准确性会下降，这表明本体感觉线索与详细的局部身体模型相结合。最后，解剖结构偏离平均值的参与者倾向于将他们的反应与典型的身体模型而非他们独特的生理结构对齐，这表明自上而下的过程会影响边界判断。我们的研究结果表明，身体边界表征将详细的三维身体模型与本体感觉反馈结合成一个解剖学身体的综合感知模型。
