A Rich Landscape of Affordances

Mark (1987) reported that observers, whose sitting capabilities had been altered by having them wear 10-cm blocks, were able to discover their own maximum height of a surface that afforded sitting on (SHmax), in the absence of an opportunity to practice sitting while wearing blocks. The current investigation attempted to identify conditions under which returning of an observer's SHmax, occurred. Returning of SH@, judgments readily occurred when observers were able to locomote between trials (Experiment 1), and rotate their heads, lean forward and to the side while making their judgments (Experiments I-2). However, they were unable to retune their SHmax, when the viewing conditions restricted all but the most basic actions (Experiments 3-5). Observers' actions during and between trials also were critical to the accuracy of their judgments when they did not wear the blocks. Overall, these findings strongly implicate observers' own activities as crucial for revealing information about their own S@ under both conditions when they are and are not familiar with their own sitting capabilities. Experiment 6 bolstered this conclusion by showing that prior practice with the act of sitting was not sufficient to enable observers to retune their own SHmax, (block condition) or to perceive their own SHmax under familiar circumstances (no block).