Abstract
BackgroundTripping is a common factor in falls and a typical safety strategy to avoid tripping on steps or stairs is to increase foot clearance over the step edge. In the present study we asked whether the perceived height of a step could be increased using a visual illusion and whether this would lead to the adoption of a safer stepping strategy, in terms of greater foot clearance over the step edge. The study also addressed the controversial question of whether motor actions are dissociated from visual perception.Methodology/Principal Findings21 young, healthy subjects perceived the step to be higher in a configuration of the horizontal-vertical illusion compared to a reverse configuration (p = 0.01). During a simple stepping task, maximum toe elevation changed by an amount corresponding to the size of the visual illusion (p<0.001). Linear regression analyses showed highly significant associations between perceived step height and maximum toe elevation for all conditions.Conclusions/SignificanceThe perceived height of a step can be manipulated using a simple visual illusion, leading to the adoption of a safer stepping strategy in terms of greater foot clearance over a step edge. In addition, the strong link found between perception of a visual illusion and visuomotor action provides additional support to the view that the original, controversial proposal by Goodale and Milner (1992) of two separate and distinct visual streams for perception and visuomotor action should be re-evaluated.
Highlights
The consequences of a fall for older adults are serious and the risk of injury, morbidity, and death from falling increases with age, with those over 75 being most vulnerable [reviewed in 1, 2]
In the present study we ask whether the perceived height of a step can be increased using a visual illusion and, more importantly, whether as a consequence this leads to the adoption of a safer stepping strategy, in terms of greater foot clearance over the step edge when stepping on to it
Perception of the height of a step was significantly affected by the configuration of the pattern superimposed on the step, with the perceived step height being larger when the narrow, vertical sine wave gratings were placed on the step riser
Summary
The consequences of a fall for older adults are serious and the risk of injury, morbidity, and death from falling increases with age, with those over 75 being most vulnerable [reviewed in 1, 2]. In the present study we ask whether the perceived height of a step can be increased using a visual illusion and, more importantly, whether as a consequence this leads to the adoption of a safer stepping strategy, in terms of greater foot clearance over the step edge when stepping on to it. Tripping is a common factor in falls and a typical safety strategy to avoid tripping on steps or stairs is to increase foot clearance over the step edge. In the present study we asked whether the perceived height of a step could be increased using a visual illusion and whether this would lead to the adoption of a safer stepping strategy, in terms of greater foot clearance over the step edge. The study addressed the controversial question of whether motor actions are dissociated from visual perception
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