Grasping New Material Densities.

IF 1.8 4区 心理学 Q3 BIOPHYSICS
Wendy J Adams, Sina Mehraeen, Marc O Ernst
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Abstract

When picking up objects, we prefer stable grips with minimal torque by seeking grasp points that straddle the object's centre of mass (CoM). For homogeneous objects, the CoM is at the geometric centre (GC), computable from shape cues. However, everyday objects often include components of different materials and densities. In this case, the CoM depends on the object's geometry and the components' densities. We asked how participants estimate the CoM of novel, two-part objects. Across four experiments, participants used a precision grip to lift cylindrical objects comprised of steel and PVC in varying proportions (steel three times denser than PVC). In all experiments, initial grasps were close to objects' GCs; neither every-day experience (metals are denser than PVC) nor pre-exposure to the stimulus materials in isolation moved first grasps away from the GC. Within a few trials, however, grasps shifted towards the CoM, reducing but not eliminating torque. Learning transferred across the stimulus set, that is, observers learnt the materials' densities (or their ratio) rather than learning each object's CoM. In addition, there was a stable 'under-reaching' bias towards the grasping hand. An 'inverted density' stimulus set (PVC 3 × denser than steel) induced similarly fast learning, confirming that prior knowledge of materials has little effect on grasp point selection. When stimulus sets were covertly switched during an experiment, the unexpected force feedback caused even faster grasp adaptation. Torque minimisation is a strong driver of grasp point adaptation, but there is a surprising lack of transfer following pre-exposure to relevant materials.

掌握新的材料密度。
当拿起物体时,我们更喜欢用最小扭矩的稳定抓地力,通过寻找跨越物体质心(CoM)的抓地点。对于同质对象,CoM位于几何中心(GC),可从形状线索计算。然而,日常物品通常包含不同材料和密度的组件。在这种情况下,CoM取决于物体的几何形状和组件的密度。我们询问参与者如何估计新奇的、由两部分组成的物体的CoM。在四个实验中,参与者使用精确的握把举起由不同比例的钢和PVC组成的圆柱形物体(钢的密度是PVC的三倍)。在所有实验中,最初的抓取接近物体的gc;无论是每天的经历(金属比PVC密度大),还是预先孤立地接触刺激材料,都不能使我们首先远离GC。然而,在几次试验中,抓地力转向了重心,减少了扭矩,但没有消除扭矩。学习在整个刺激集中转移,也就是说,观察者学习材料的密度(或它们的比率),而不是学习每个物体的CoM。此外,对抓握的手有稳定的“欠伸”倾向。“反向密度”刺激集(PVC的密度是钢的3倍)诱导了类似的快速学习,证实了材料的先验知识对抓点选择的影响很小。当刺激组在实验过程中被秘密切换时,意想不到的力反馈会导致更快的抓取适应。扭矩最小化是抓地点适应的强大驱动力,但在预暴露于相关材料后,令人惊讶的是缺乏转移。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Multisensory Research
Multisensory Research BIOPHYSICS-PSYCHOLOGY
CiteScore
3.50
自引率
12.50%
发文量
15
期刊介绍: Multisensory Research is an interdisciplinary archival journal covering all aspects of multisensory processing including the control of action, cognition and attention. Research using any approach to increase our understanding of multisensory perceptual, behavioural, neural and computational mechanisms is encouraged. Empirical, neurophysiological, psychophysical, brain imaging, clinical, developmental, mathematical and computational analyses are welcome. Research will also be considered covering multisensory applications such as sensory substitution, crossmodal methods for delivering sensory information or multisensory approaches to robotics and engineering. Short communications and technical notes that draw attention to new developments will be included, as will reviews and commentaries on current issues. Special issues dealing with specific topics will be announced from time to time. Multisensory Research is a continuation of Seeing and Perceiving, and of Spatial Vision.
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