Visual Perception of Motion and Texture

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This research is aimed at the long-term objective of understanding human visual perception, particularly low-level mechanisms that are functionally relevant to animals and people in everyday life. This particular work is focused on how elementary aspects of the visual world, such as luminance, contrast, texture, motion and colour, are used by the human brain to see objects stand out from their backgrounds (figure-ground segmentation), and to judge relative depths of objects at different distances. The projects will answer questions about (1) the role of higher-order image statistics (e.g. sparseness, local edge structure) in texture segmentation; (2) the role of luminance and colour in texture segmentation; (3) how motion parallax performance depends on surface texture; and (4) the implications of imperfect gaze behaviour during motion parallax. These goals will be achieved using quantitative psychophysical experiments and eye movement recording, with mathematical models which are tested on psychophysical data. Novel methodological aspects include (1) the quantitative study of motion parallax using modern computer graphics rendering, (2) the construction of visual stimuli from natural images or our recently developed synthetic textures designed to mimic the statistics of natural images, and (3) detailed analysis of gaze direction during motion parallax psychophysics. Figure-ground segmentation is a key problem in vision research, going beyond our present knowledge of early visual processing and a necessary precursor to subsequent object recognition, spatial cognition, and visuomotor control - until now it has been studied using highly artificial stimuli. This research is primarily directed towards improving our basic understanding of visual perception, particularly in the context of more naturalistic situations, e.g. motion parallax and complex textures. In the longer term, the results may contribute to innovations in computer vision, virtual reality displays, and the design of clinical diagnostic stimuli for assessing visual impairment.