School of Kinesiology, The University of Western Ontario, Canada.
Brain Cogn. 2013 Jun;82(1):18-24. doi: 10.1016/j.bandc.2013.02.005. Epub 2013 Mar 16.
An issue of continued debate in the visuomotor control literature surrounds whether a 2D object serves as a representative proxy for a 3D object in understanding the nature of the visual information supporting grasping control. In an effort to reconcile this issue, we examined the extent to which aperture profiles for grasping 2D and 3D objects adheres to, or violates, the psychophysical properties of Weber's law. Specifically, participants grasped differently sized 2D and 3D objects (20, 30, 40, and 50mm of width) and we computed the just-noticeable-difference scores associated with aperture profiles at decile increments of normalized grasping time. The aperture profiles for 2D objects showed an early through late (i.e., 10% through 90%) adherence to Weber's law, whereas the late stages of grasping 3D objects (i.e., >50% of grasping time) produced a fundamental violation of the law's principles. As such, results suggest that grasping a 2D object is a top-down and cognitive task mediated via relative visual information. In contrast, the enriched shape information provided by a 3D object (i.e., stereoscopic vergence and disparity cues) allows for later aperture specification via absolute (Euclidean) visual information. Most notably, our results establish that the dimensional properties of an object influence the visual information mediating motor output, and further indicate that 2D and 3D objects are not representative proxies for one another in understanding the visual control of grasping.
在视觉运动控制文献中，一个持续存在争议的问题是，2D 物体是否可以作为理解支持抓握控制的视觉信息本质的 3D 物体的代表代理。为了解决这个问题，我们研究了抓握 2D 和 3D 物体的孔径曲线在多大程度上符合或违反 Weber 定律的心理物理学特性。具体来说，参与者抓握不同大小的 2D 和 3D 物体（20、30、40 和 50mm 的宽度），我们计算了与孔径曲线相关的可察觉差异分数，这些分数与归一化抓握时间的十分位数增量有关。2D 物体的孔径曲线表现出早期到晚期（即 10%到 90%）对 Weber 定律的遵守，而 3D 物体的晚期抓握阶段（即>50%的抓握时间）则违反了该定律的原则。因此，结果表明，抓握 2D 物体是一种自上而下的认知任务，通过相对视觉信息进行介导。相比之下，3D 物体提供的丰富形状信息（即立体视差和视差线索）允许通过绝对（欧几里得）视觉信息进行后期孔径指定。值得注意的是，我们的结果表明，物体的维度特性会影响介导运动输出的视觉信息，并且进一步表明，2D 和 3D 物体在理解抓握的视觉控制方面不是彼此的代表代理。
