Critical Boundaries for Perceiving Affordances in Stairclimbing

• Published in: Journal of sport & exercise psychology 2000-06, Vol.22
• Main Author: Maraj, B
• Format: Article
• Language: English
• ISSN: 0895-2779

The purpose of this experiment was to investigate if perception of pitch angle alone could used to detect the climbability of stairs. A custom-built stair apparatus that could mechanically alter the riser height and tread depth was used. Tread depth and riser heights were independently varied to give combinations of pitch angles that ranged from 20 deg. to 80 deg. (altered in increments of 5 deg). Participants (n = 5) viewed, in a randomized fashion, 26 different combinations of stair set dimensions (with each pitch angle represented two times). Participants viewed the stair sets from a distance of 1.5 m and were asked to determine if the stair set was climbable and to give an indication of their confidence (1-low to 7-high) about that determination. The results indicated that, at pitch angles greater than 65 deg, the stairs were not perceived as being climbable by any of the participants; a decision in which they were all very confident (6.3). If this were a critical boundary, one would expect participants to exhibit less confidence in their determination of climbability at the pitch angles immediately below this. Confirming this hypothesis, pitch angles at 60 and 65 deg. revealed considerably lower overall confidence values (4.1) regardless of the determination of climbability. Further support for critical boundaries was gleaned from calculating the stair diagonal relative to each participants leg length (D/L). When this body-scaled metric reached a value between .83 and .89, the stair sets were not perceived as being climbable. For all participants, these proportion of leg length values occurred at pitch angles of 65 deg or greater. Results are discussed as they relate to perceiving affordances for stairclimbing.