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Alexander Rose-Henig, Arthur Shapiro; A comparison of hypocycloid perception produced by two different elemental constructions. Journal of Vision 2013;13(9):819. doi: https://doi.org/10.1167/13.9.819.
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A hypocycloid is a geometrical construction in which a smaller inner circle rolls inside the circumference of a larger outer circle. Many researchers (e.g., Galileo; Johansson; Cutting and Proffitt) have been interested in the perception hypocycloidal motion, in part, because the information provided by points on the inner circle’s circumference (the local motion) does not always predict the inner circle’s path (the global organization). To investigate the perceptual organization found in hypocycloid motion, we compare two novel stimulus constructions: In Construction 1 a hypocycloid percept emerges from the motion of several individual dots that oscillate in straight lines through the center of the outer circle; in Construction 2, a hypocycloid percept emerges when the dots follow circular paths. For both constructions the key element for producing the hypocycloid pattern is the adjustment of the relative temporal phase of each of the dots (e.g., for construction 1, a 0° dot moves left/right, a 90° dot moves up/down, etc; the perception of a hypocycloid arises when the timing of each dot is shifted so that their temporal phases match the angle of their paths’ separation). Here we show how these constructions produce "illusions" that can serve as powerful tools to investigate interactions between color, motion, attention, and perceptual grouping. For instance, we show that the global hypocycloid pattern is robust enough to be maintained even when physical lines or circles accentuate the local path of each dot; however, relatively small changes in the relative temporal phase can disrupt the global perception. Also, because Constructions 1 and 2 produce rotating circles with different internal rotation patterns, combinations of the two Constructions lead to a bi-stable image, whose rotational characteristics can be altered when the observer shifts attention to different cues placed on the circular paths.
Meeting abstract presented at VSS 2013
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