Does my step look big in this? A visual illusion leads to safer stepping behaviour.
BACKGROUND
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 also addressed the controversial question of whether motor actions are dissociated from visual perception.


RESULTS
21 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
The 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.
Elliott
David B
DB
Bradford School of Optometry & Vision Science, University of Bradford, Bradford, West Yorkshire, United Kingdom. d.elliott1@bradford.ac.uk
Vale
Anna
A
Whitaker
David
D
Buckley
John G
JG
D000058:Accidental Falls / Q000517:prevention & control*; D005528:Foot / Q000502:physiology; D006801:Humans; D009068:Movement; D009903:Optical Illusions / Q000502:physiology*; D011597:Psychomotor Performance; D012449:Safety; D013028:Space Perception; D014034:Toes / Q000502:physiology; D055815:Young Adult