Frediani Gabriele, Carpi Federico
Biomedical Engineering Unit, Department of Industrial Engineering, University of Florence, Florence, Italy.
Rehabilitation Centre, IRCCS Fondazione don Carlo Gnocchi ONLUS, Florence, Italy.
J Neural Eng. 2024 Dec 27;21(6). doi: 10.1088/1741-2552/ada0e8.
. The perception of softness plays a key role in interactions with various objects, both in the real world and in virtual/augmented reality (VR/AR) systems. The latter can be enriched with haptic feedback on virtual objects' softness to improve immersivity and realism. In such systems, visual expectation can influence tactile sensitivity to softness, as multisensory integration attempts to create a coherent perceptual experience. Nevertheless, expectation is sometimes reported to attenuate, and other times to enhance, perception. Elucidating how the perception of softness is affected by visual expectation in VR/AR is relevant not only to the neuropsychology and neuroscience of perception, but also to practical applications, such as VR/AR-based training or rehabilitation.Here, by using novel wearable tactile displays of softness previously described by us, we investigated how the sensitivity to softness in a visuo-tactile VR platform can be influenced by expectation. Twelve subjects were engaged in comparing the softness of pairs of virtual objects, familiar or not, with tactile feedback of softness and visual expectation either conflicting or not. The objects' Young's moduli were initially randomly selected from a large set, spanning two orders of magnitude (0.5, 2, 20, 50 and 100 MPa), and then their difference was iteratively reduced, to reach the just noticeable difference in softness.For the intermediate modulus, a conflict between tactile feedback and visual expectation caused a statistically significant increase in sensitivity.This finding supports the theory that there can be conditions in which contradictory stimuli strengthen attention (to resolve conflicting sensory information), which in turn can reverse the sensory silencing effect that expectation may otherwise have on perception.
柔软度的感知在与各种物体的交互中起着关键作用，无论是在现实世界还是在虚拟/增强现实（VR/AR）系统中。后者可以通过对虚拟物体柔软度的触觉反馈来丰富，以提高沉浸感和真实感。在这样的系统中，视觉预期可以影响对柔软度的触觉敏感度，因为多感官整合试图创造一种连贯的感知体验。然而，有时据报道预期会减弱感知，而有时又会增强感知。阐明在VR/AR中柔软度感知如何受到视觉预期的影响，不仅与感知的神经心理学和神经科学相关，也与实际应用相关，如基于VR/AR的训练或康复。在此，我们使用我们之前描述的新型可穿戴柔软度触觉显示器，研究了在视觉-触觉VR平台中对柔软度的敏感度如何受到预期的影响。12名受试者参与比较成对虚拟物体的柔软度，这些物体熟悉或不熟悉，同时伴有柔软度的触觉反馈和视觉预期，二者可能冲突也可能不冲突。物体的杨氏模量最初从一大组中随机选择，范围跨越两个数量级（0.5、2、20、50和100兆帕），然后迭代减小它们之间的差异，以达到柔软度的刚刚可察觉差异。对于中间模量，触觉反馈和视觉预期之间的冲突导致敏感度在统计学上显著增加。这一发现支持了这样一种理论，即存在一些情况，矛盾的刺激会增强注意力（以解决相互冲突的感官信息），这反过来又可以逆转预期可能对感知产生的感官沉默效应。
