InfoBox：

中文名：虚拟现实中的具身存在感

外文名：Virtual Embodiment

学科：人机交互、虚拟现实、虚拟化身

实质：人在沉浸式虚拟现实环境中对代表其真实身体的虚拟化身及其身份所产生的拥有、自主控制和所处位置的主观感受。

研究背景：

从Jaron Lanier在1980年代在媒体上推广Virtual Reality (VR)，虚拟现实, 这一术语到2022年，虚拟现实的发展由于硬件技术的限制几经波折。虚拟现实被普遍定义可以提供听觉、视觉、触觉等感知觉反馈的有计算机模拟出来的可交互的虚拟环境 (Jerald, 2016)。临场感是指当用户处于由沉浸式VR所构建的虚拟世界时，用户接收到虚拟世界中的多通道感知觉实时反馈、感受到身临其境，从而产生认知和心理层面的改变。其中，具身感是临场感的重要组成部分。

具身感 (the sense of embodiment, SoE) 主要探索人对身体的感受和认知，这里的身体是指可以被医学科学和实践的主体和客体 (Gallagher, 2001)。具身感这一概念在哲学领域的探索和发展由来已久，经常被用来探索身体和意识的关系。当下，具身感在哲学、认知心理学、媒介技术/传播学、神经科学、医学等不同领域具有多样的定义。比如在认知心理学领域，Kilteni et al. 认为，虚拟现实中的具身感描述了用户同时产生的在一个身体里、拥有一个身体、并能够控制这个身体的整体感受。Kilteni et al. (2012) 基于虚拟环境中对虚拟身体感受的大量研究，归纳了理论框架：包括用户对身体的拥有感 (sense of ownership, SoO)、对身体的控制感 (sense of agency, SoA)、以及在身体中的位置感 (sense of self-location)。这一具身感的定义和框架被后续研究大量引用并接受。这里，本文作者基于文献给出对虚拟具身感 (virtual embodiment)的理解定义：人在沉浸式虚拟现实环境中对代表其真实身体的虚拟化身及其身份所产生的拥有、自主控制和所处位置的主观感受。

研究概况：

因为人的自我是不能脱离身体而单独存在，所以采用实验的方法来操控人的具身感受是具有挑战的。因而，许多研究科学家尝试采用不同的方法来操控“被认可”的身份的身体一部分作为替代，如橡胶手、假手、镜子反射等方式，来控制人的具身感受。基于经典的橡胶手错觉 (rubber hand illusion, RHI) 实验，许多认知心理学家陆续研究了不同条件下，人对于虚假身体的具身感受并主要测量了人对虚假身体的拥有感，例如人体模型 (Petkova & Ehrsson, 2008)、镜子里的反射 (Ramachandran et al., 2009) 。

约15年前，Slater et al.首次在虚拟现实环境中复制了RHI 的研究，他尝试使被试的注意力脱离自身的身体并完全集中在虚拟的手上，通过为被试提供虚拟手的视觉和触觉刺激使其产生了对虚拟手的拥有感 (Slater et al., 2008, 2010)，这一现象被称为虚拟手错觉 (virtual hand illusion, VHI) 或者虚拟身体错觉 (virtual body illusion, VBI)。后续研究陆续证实人们可以从虚拟化身的角度看到虚拟现实中的世界，并感受“拥有”或者“控制”虚拟化身 (Banakou et al., 2013; Gilpin et al., 2014; Bertrand et al., 2018)。之后，科学家们分别尝试操控虚拟手臂和虚拟身体的结构、形状、颜色、大小、和位置等外形或运动等表征，以探索不同的外形和运动表征对于具身感受的影响 (Kilteni et al., 2012; Banakou et al., 2013; Peck et al., 2013)。这些虚拟身体的外形或运动等表征在物理现实中不会出现，甚至可能与我们的真实身体完全不同。实验表明，对虚拟身体的视觉运动操控，可能会影响人的真实生理反应 (Martini et al., 2013; Bergstr?m et al., 2016)，甚至还可能会调节被试的行为反应 (Osimo et al., 2015; Seinfeld et al., 2018)。

近年来，除了进一步对于具身感受的意识进行身体和意识关系的研究之外 (Steptoe et al., 2013; Tong et al., 2016)，学术界多项研究主要对虚拟具身感受在两个方面进行了应用和研究：(1) 应用心理治疗、康复、和神经科学等领域 (Tarr & Warren, 2002; Martini et al., 2016; Riva et al., 2018; Tong et al., 2020a, 2021)，如帮助病人解决慢性疼痛等问题；(2) 转换视角，提高对少数人群或弱势群体的同理心并降低偏见(Tong et al., 2017, 2020b, 2021)。在具身感和痛觉研究领域，Matamala-Gomez et al. 发现观看健康的假手并对其产生具身体验可以抑制体感区域中与疼痛相关的神经活动 (2019)，Longo et al. (2012) 此前的神经影像学研究也证明了这一发现。此外，对于不同虚拟身体表征和具身感的研究发现，由外形或运动表征引起的具身感变化和痛觉的变化有显著相关性，而具体的相关关系取决于具体的表征情况，比如，肤色 (Martini et al., 2013)、皮肤透明度 (Martini et al., 2015)、大小尺寸 (Romano et al., 2016) 、外形的真实/抽象程度 (Zanini et al., 2017)、和虚拟身体与真实身体运动的同步异步情况等 (Martini et al., 2014; Zanini et al., 2017)。

在具身感和同理心研究领域，现有研究结果发现虚拟现实中的具身感受允许人更好的“设身处地”的站在别人的视角思考，并降低人们的隐性偏见并提高其同理心 (Petkova & Ehrsson, 2008; Banakou et al., 2013; Cummings & Bailenson, 2015)。具身感被广泛的用于尝试减少性别和种族偏见(Peck et al., 2013; Maister et al., 2015; Banakou et al., 2016; Lopez et al., 2019)，此外也被用于降低对儿童群体的隐性偏见 (Banakou et al., 2013) 和改变人在特殊场景下的行为决策 (Rosenberg et al., 2013)。

在人机交互领域，相关研究进一步探索用户维持具身感与“用户-虚拟化身”运动一致性的定量关系(Zhipeng et al., 2022)，以及利用用户与虚拟化身的运动不一致性，来实现运动重定向(Eric et al., 2019; Rietzler et al., 2020)，物体重量（Samad et al., 2019）和物体触觉（Rietzler et al., 2018）的通感模拟，以及优化用户的交互姿态及相应交互舒适度（Tianren et al., 2022）。

未来展望：

虽然目前的科技手段无法将人从虚拟身体经历的感知觉全方面模拟出来，产业界一直在开发虚拟现实技术相关的各种硬件计算和传感设备，并提高其性能，以提高“技术具身”中技术的质量、让人更自然的通过真实身体拥有和控制虚拟身体，提高用户在各种场景中的具身体验。比如，Noitom, Tesla Suit 和 Hardlight VR等虚拟现实技术公司为了给用户提供更加生动逼真的触觉反馈，研发了全身的触感套装。Meta致力于将用户脸部表情和全身肢体运动情况同步到虚拟身体中，以提高虚拟身体之间的社交效果。与此同时，产业界也积极探索虚拟现实中的具身感对各种产业应用的意义和其可能带来更加积极影响，如游戏、电影、竞技运动、元宇宙等社交娱乐行业，职业技能培训等教育场景，和远程会议等领域。如何在虚拟现实环境中为人构建基于真实甚至超出真实的“技术身体”的具身认知体验，是值得未来学术界和产业界共同探索的一重要研究方向和议题，也会进一步推动所有技术领域中人机交互、人机共生、人机共融的和谐前景。

小结：

本文主要介绍了沉浸式虚拟现实环境中给人带来的最重要感觉，临场感(或存在感)，并侧重介绍了具身认知目前在学术界的研究现状和现阶段所遇到的问题，以便未来在人机交互领域中，研究人员可以更好的探索沉浸式虚拟现实环境是如何改变人的认知和行为。

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