Perceptual judgments for stair climbing as a function of pitch angle

Two experiments explored perception and action for stair climbing, with manipulations to the stair dimensions. In Experiment 1, a custom-built apparatus manipulated the stair dimensions, while three groups of participants made perceptual judgments of climbability. The groups differed significantly for absolute leg length (p < .0001), but there was no significant difference between the groups when stair dimensions were calculated relative to leg length. The selected tread depths and riser heights reflected constant proportions of participants' leg length. Using the pitch angles formed as a composite metric, the results revealed that all groups selected 60 degrees as the limit for climbability. Experiment 2 scaled pitch angle systematically from 20 degrees to 80 degrees, and participants judged 65 degrees and beyond to be unclimbable. These results provided evidence that pitch angle might be used in perceptual judgments for stair climbability.