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SM Menees, F Stuerzel, L Spillmann; Speed, Width, and Fixation Effects on the Perception of a Moving Dark Phantom . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4732.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We investigated three factors related to the perception of a moving dark visual phantom (VP) in order to test the limits of the illusory perception. A moving dark VP was defined as the perception of an illusory darker region that appears to be a solid object with real borders and to move like a real object. Methods: Three observers with normal or corrected-to-normal vision participated in the experiment. The dark VP was produced by switching on and off, sequentially from left to right, vertical rows of lights in an array of lights on a computer monitor. The sequential speed at which the lights were turned on and off (number of VPs/sec presented) and the width of the dark area between them (width in degrees of visual angle) were manipulated as was the method of observation. That is, observations were conducted while fixated and while tracking. Viewers reported whether or not they perceived the dark VP. They also reported on the quality of the perception. Results: Results indicate that as the sequential rate at which the lights were turned on and off increased, the perception of the dark VP as an object with distinct edges decreased. Wider widths (1.5 - 3.75 degrees of visual angle) of the dark VP region produced more stable images than narrow ones (less than1.5 degrees of visual angle). An interaction between speed and width was also observed. At slow sequential illumination rates (less than 0.6 VPs/sec) the VP remained stable while tracking, but at higher sequential illumination rates (greater than 1.6 VPs/sec) tracking resulted in a decreased perception of the dark VP. This effect was less pronounced for wider VPs (at least 1.5 degrees of visual angle). Fixation worked better for perceiving stable VPs at faster sequential illumination rates (greater than1.6 VPs/sec), while tracking worked better for perceiving stable VPs at slower rates (less than 0.6 VPs/sec). Conclusion: The visual system appears able to integrate spatial information across wide regions (3.75 degrees of visual angle) to produce an illusory dark VP. Differences related to the sequential illumination rate will be discussed in terms of foveal versus peripheral mechanisms.
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