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JongJin Kim, Laurence Harris; Perceived size during visually simulated self-motion. Journal of Vision 2018;18(10):792. doi: 10.1167/18.10.792.
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© ARVO (1962-2015); The Authors (2016-present)
INTRODUCTION The perceived distance to objects in the environment needs to be updated during self-motion. Such updating needs to be overridden if the object moves with the observer (such as when reading a phone while walking). Errors in updating could lead to errors in perceived distance and, because of size/distance invariance, to errors in perceived size. To look for such errors, we measured the perceived size of an object that moved with the observer during visually simulated self-motion. METHODS Participants judged whether a vertical rod presented on the ground plane in a virtual-reality-simulated scene at a fixed distance of 2-10m, was longer or shorter than a physical rod (45cm) that they held in their hands either vertically or horizontally. Observers were either stationary or in the presence of optic flow compatible with moving at 1m/s or 10m/s forwards or backwards. Viewing was monoscopic or stereoscopic. Responses were fitted with a logistic to determine the PSE. RESULTS The rod generally needed to be larger than the physical rod to be judged as equal to its size. Errors were smaller when viewing monoscopically compared to stereoscopically (+16%). The orientation of the reference rod influenced size judgements, with larger errors when held horizontally (+16%) compare to when held vertically (+6%). However, there were no significant differences observed in the errors in perceived rod size due to optic flow. CONCLUSION We interpret the changes in the perceived size as resulting from an error in perceived distance. Thus, we confirm the well-known observation that perceived distances are compressed in a virtual environment. However, this compression effect disappeared with monoscopic viewing, despite fewer cues to distance. Our ability to update the distance of an object moving with us appears to be robust during forward and backward self-motion.
Meeting abstract presented at VSS 2018
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