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Helen Clark, John Perrone; To fixate or pursue? Manipulating eye movements to combat the size-speed illusion. Journal of Vision 2016;16(12):1345. doi: 10.1167/16.12.1345.
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© ARVO (1962-2015); The Authors (2016-present)
The size-speed illusion is where longer objects moving in depth are judged to be moving slower than shorter objects travelling at the same speed. This may have consequences in the judgement of approaching vehicles and could account for vehicle collisions at level-crossings. Recently it has been shown that the size-speed illusion may be related to the movement of our eyes. Clark, Perrone, Isler and Charlton (AA&P, 2016) found that when observers tracked trains and cars in a simulated environment, their eye movement behaviour was different when they judged the speed of the longer train compared to the smaller car. Eye fixations were localised around the visual centroid of the train and consequently were further from the front of the train compared to the car. It has also been found that the magnitude of the size-speed illusion can be reduced by manipulating eye movements (both smooth pursuit and fixations), with the use of tracking dots placed at strategic locations on the vehicles or by placing a reference marker in the surrounding environment (Clark et al., 2016). Using this information, three level-crossing collision preventative measures were investigated in an applied setting designed to manipulate observer eye movements: (1) Alternating flashing lights placed on the front of trains. (2) Marker poles beside the railway line and (3) A mesh 'windbreaker' screen along part of the railway line. Results show that the flashing light intervention had the greatest effect; observers consistently judged a train with flashing lights to be moving faster than a regular train moving at the same speed. The poles had a smaller effect, while there was no discernable effect in speed discrimination between the mesh fence condition and a regular train. Our results show that interventions designed to influence smooth pursuit are the most effective in the vehicle speed discrimination task.
Meeting abstract presented at VSS 2016
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