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Shree Venkateshan, Allison Sekuler, Patrick Bennett; Effect of manipulating appearance of stairs on perceived step height. Journal of Vision 2020;20(11):1438. doi: https://doi.org/10.1167/jov.20.11.1438.
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Falls on stairs affect people of all ages, and are a leading cause of injury and accidental death among older adults. One strategy that can reduce falls walking up stairs is to lift the foot slightly higher than the minimum height that is required to clear the step's leading edge. Visual cues can encourage people to adopt this strategy by constructing steps that are perceived as being slightly higher than their veridical height. Elliot et al. (2009) found that placing high contrast, vertical gratings on a step increased the perceived height of that step compared to steps without the gratings. The present study attempted to replicate these findings. We measured the perceived height of steps that contained high contrast, vertical square wave textures with spatial frequencies of 4, 12, and 20 cy/step. Stimuli were line drawings of stairs containing three steps. On each trial, subjects were shown two sets of stairs: one that contained the high-contrast texture on the bottom step (test step), and another that did not contain the texture (reference step), and judged which stairs contained the taller bottom step. The height of the reference step varied across trials using the method of constant stimuli, and we derived the point of subjective equality from psychometric functions. Results from 22 young adults showed that the presence of the texture increased the perceived height of the step by 5%, and that the size of the effect was nearly constant across spatial frequencies. This result suggests the perceived height of a step can indeed be affected by a simple visual illusion, which might lead to a safer stepping strategy. Currently we are examining how age and the effects of other parameters of the textures impacts perceived step height.
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