Hajnal Alen, Wagman Jeffrey B, Doyon Jonathan K, Clark Joseph D
Department of Psychology, University of Southern Mississippi, USA
Department of Psychology, Illinois State University, USA.
Perception. 2016 Jul;45(7):768-86. doi: 10.1177/0301006616638597. Epub 2016 Mar 14.
Past research has shown that haptically perceived surface slant by foot is matched with visually perceived slant by a factor of 0.81. Slopes perceived visually appear shallower than when stood on without looking. We sought to identify the sources of this discrepancy by asking participants to judge whether they would be able to stand on an inclined ramp. In the first experiment, visual perception was compared to pedal perception in which participants took half a step with one foot onto an occluded ramp. Visual perception closely matched the actual maximal slope angle that one could stand on, whereas pedal perception underestimated it. Participants may have been less stable in the pedal condition while taking half a step onto the ramp. We controlled for this by having participants hold onto a sturdy tripod in the pedal condition (Experiment 2). This did not eliminate the difference between visual and haptic perception, but repeating the task while sitting on a chair did (Experiment 3). Beyond balance requirements, pedal perception may also be constrained by the limited range of motion at the ankle and knee joints while standing. Indeed, when we restricted range of motion by wearing an ankle brace pedal perception underestimated the affordance (Experiment 4). Implications for ecological theory were offered by discussing the notion of functional equivalence and the role of exploration in perception.
过去的研究表明，通过足部触觉感知到的表面倾斜度与视觉感知到的倾斜度的匹配系数为0.81。视觉上感知到的坡度比不看时站在上面时显得更平缓。我们试图通过要求参与者判断他们是否能够站在倾斜的斜坡上来找出这种差异的来源。在第一个实验中，将视觉感知与踏板感知进行了比较，在踏板感知中，参与者用一只脚向一个被遮挡的斜坡迈出半步。视觉感知与人们实际能够站立的最大坡度角密切匹配，而踏板感知则低估了它。在向斜坡迈出半步的踏板条件下，参与者可能不太稳定。我们通过让参与者在踏板条件下抓住一个坚固的三脚架来控制这一点（实验2）。这并没有消除视觉和触觉感知之间的差异，但当坐在椅子上重复这项任务时差异消除了（实验3）。除了平衡要求外，踏板感知还可能受到站立时踝关节和膝关节有限活动范围的限制。事实上，当我们通过佩戴脚踝支具来限制活动范围时，踏板感知低估了这种可及性（实验4）。通过讨论功能等效性的概念以及探索在感知中的作用，为生态理论提供了启示。
