Multiple-stage ambiguity in motion perception reveals global computation of local motion directions

Rider, Andrew T. and Nishida, Shin'ya and Johnston, Alan (2016) Multiple-stage ambiguity in motion perception reveals global computation of local motion directions. Journal of Vision, 16 (15). 7/1-7/11. ISSN 1534-7362

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Abstract

The motion of a 1D image feature, such as a line, seen through a small aperture, or the small receptive field of a neural motion sensor, is underconstrained, and it is not possible to derive the true motion direction from a single local measurement. This is referred to as the aperture problem. How the visual system solves the aperture problem is a fundamental question in visual motion research. In the estimation of motion vectors through integration of ambiguous local motion measurements at different positions, conventional theories assume that the object motion is a rigid translation, with motion signals sharing a common motion vector within the spatial region over which the aperture problem is solved. However, this strategy fails for global rotation. Here we show that the human visual system can estimate global rotation directly through spatial pooling of locally ambiguous measurements, without an intervening step that computes local motion vectors. We designed a novel ambiguous global flow stimulus, which is globally as well as locally ambiguous. The global ambiguity implies that the stimulus is simultaneously consistent with both a global rigid translation and an infinite number of global rigid rotations. By the standard view, the motion should always be seen as a global translation, but it appears to shift from translation to rotation as observers shift fixation. This finding indicates that the visual system can estimate local vectors using a global rotation constraint, and suggests that local motion ambiguity may not be resolved until consistencies with multiple global motion patterns are assessed.

Item Type: Article
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Psychology
Identification Number: 10.1167/16.15.7
Depositing User: Eprints, Support
Date Deposited: 01 Mar 2017 11:41
Last Modified: 13 Oct 2017 01:38
URI: http://eprints.nottingham.ac.uk/id/eprint/40945

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