Motion-induced position shifts in visual perception tasks and eye movement

• Main Author: Forster, J.
• Published: City, University of London 2018
• Subjects: RE Ophthalmology
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.753651

Movement has an effect upon the perceived spatial position of moving objects, such that they are not perceived at their instantaneous spatial position. Vision scientists named this phenomenon motion-induced position shift (MIPS). The reason, neural loci, and the mechanisms causing the positional illusion have challenged scientists over the last century. Nowadays, many vehicles, such as cars, planes and submarines are equipped with onboard computers containing touchscreens. Active controls of those on-board computers require visuomotor-actions, which could be affected by perceptual illusions, but also require time, and attention. Hence, it is becoming more crucial to fully understand how the visual system generates visuomotor-guided actions, and how it copes with visual illusions. Human-machine interactions could be designed such that perceptual illusions would be 1) avoided, or 2) predicted, and considered in human actions, or such that 3) the user interacted with visuomotor actions that resisted visual illusions. One alternative to finger points towards on-board computers is saccadic eye movements. The saccadic system is very fast, and therefore, would not require as much time and attention as a finger point task towards the touch screen. Saccades are constantly facing the challenge of localising objects, which makes it interesting to study how they cope with visual illusions like the motion-induced position shift. The purpose of this thesis was to establish if the saccadic system was affected by the motion-induced position shift in the same manner as the perceptual system was affected. I confirmed that movement had an effect upon the perceived spatial position of moving objects in perception-tasks and in volitional saccades. A previous study showed that reflexive saccades resisted the illusion, indicating that they were more accurate than other visually guided actions. I replicated these results, but claimed that the results are not representative. As a consequence, there is no evidence that reflexive saccades do escape the visual illusion while volitional saccades do not.