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mike tymoski, Jessica Witt; Affording Both: Do the Same Underlying Mechanisms Account for Action-specific and Affordance Perception?. Journal of Vision 2018;18(10):1268. doi: 10.1167/18.10.1268.
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Some researchers speculate that action-specific effects, like the distance on hill (DoH) effect – where individuals perceive distances on hills as farther than equal distances on flat ground, due to an increased energetic cost to walk those distances – are simply spatial judgments grounded in perceived affordances, or environmentally supported opportunities to act. Essentially, the claim is that action-specific effects are misinterpreted evidence for affordance perception. If action-specific effects were simply affordance judgments converted to spatial estimates, participants who were more accurate at judging affordances would also be more likely to show a larger DoH effect. To test this prediction, we measured the magnitude of the DoH effect and compared it with accuracy on an affordance task. Previously, the affordance task was to estimate passability of doorways of various widths. We found no correlation between performance on the two, r= -0.036, p=0.753; which we then replicated, r= -.0891, p=0.441. However, the affordance task related to body size, whereas the DoH effect is a function of energetic demands. Thus, in a new study, we developed and used a novel energetics-based affordance task. In VR, participants judged whether they would be able to run through a dynamic aperture that was placed 10 meters up a 30 degree hill and that closed at 1 of 8 speeds. Just noticeable difference (JND) scores were calculated to determine each participant's sensitivity to change in afforded passability as a function of closing speed. Once again we found a significant DoH effect, t(42)= 3.17, p=0.003, and good reliability and variability in performance for both tasks, but no correlation between performance on the two tasks, r=-0.066, p=0.669. These results, in conjunction with our previous findings, suggest that action-specific and affordance perception are distinct phenomena, and rely on different mechanisms.
Meeting abstract presented at VSS 2018
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