站立情境與知覺系統引致之登階高度環境賦使

Affordances for Stair Climbing Is Induced by Standing Conditions and Perceptual Systems

生態心理學的環境賦使旨在說明個體與環境之間的特定關係，其認為兩者的屬性具有相互參照的關聯性，此關係可透過身體尺度的概念加以描述。本研究基於生態手段，探討觸動覺與視覺導引登階動作的可能性，藉由改變個體站立高度，檢視知覺最大登階高度之環境賦使。24名成人被招募為實驗參與者，隨機分派至觸動覺與視覺評估兩組；參與者需評估能否以抬起單腳之動作攀登台階，其知覺判斷的方式有二：分別為視覺觀察與操作盲人手杖進行探索。實驗安排參與者站立於真實地板、高10 cm之升高地板、以及穿著高10 cm的積木鞋共三種情境。運用可調整高度之台階擷取參與者的知覺最大登階高度，並依據腿長計算登階高度之關鍵比值。實驗結果發現最大登階高度之環境賦使不受個體站立情境改變而影響其判斷，個體腿長與台階結構的關係會維持不變的特徵。儘管個體藉由不一樣的知覺系統判斷最大登階高度，不過在準確性與評估信心上無明顯不同，本研究之發現與知覺系統對等的觀點一致。以觸動覺系統探索登階高度的環境賦使，可能無法只參照個體腿長作解釋，未來研究可檢證如身體部位與器物屬性等影響因素，以更明確地探知登階動作的環境賦使。

Affordances in ecological psychology refer to a specific relation between the individuals and their environment. The definition for the properties of environment should refer to the characteristics of animals and be interpreted through the concept of body scale. This study, based on the ecological approach, was designed to investigate haptically and visually guided stair climbability. Affordances were examined for perceived maximum riser heights by changing individual's standing heights. Twenty-four adults were recruited, and randomly assigned to either haptic judgement group or visual judgement group. Participants were asked to judge whether each stair height is climbable if raised single leg only. The judgments were made through two perceptual modalities, viewing and exploring with a white cane. Three experimental conditions were arranged when participants made their judgments either standing on the real floor, standing on 10-cm height raised floor, or wearing 10-cm height blocks. An adjustable stair was used to measure perceived maximum raiser heights of participants, and the critical ratio was calculated by comparing the height to the leg length of participants. The results showed that perception of affordances for maximum riser heights would not be influenced by standing heights. The relation between the lengths of the individual's legs and the stair heights would maintain invariant. Despite individuals perceived maximum raiser heights with different perceptual systems, the accuracy and confidence of haptic and visual judgment did not differ. Our finding was identical with the viewpoint of perceptual equivalence. The perceived maximum raisers height by the haptic exploration might not be specified merely by the concept of body scale with leg length. Future research could examine the factors such as the properties of body components and objects to clarify the affordances of climbing stair.