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Michael Morgan, Donald MacLeod; Non-orthogonal channels for relative numerosity and contrast detection. Journal of Vision 2014;14(10):392. doi: 10.1167/14.10.392.
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Non-orthogonal channels for relative numerosity and contrast detection Previous studies with spatially-sampled luminance gratings have shown reciprocity between luminance and dot density for detection1 and accurate interpolation between samples for vernier acuity2. We extended these investigations to contrast and numerosity-modulated sine-wave gratings using a 70 x 70 sampling grid of Gaussian-shaped dots that were randomly assigned to be increments or decrements on a mean-luminance background, with a contrast that was modulated sinusoidally in one dimension over the pattern. Numerosity was modulated either by one-dimensional sinusoidal modulation of dot probability (present/absent) or by one-dimensional modulation of nearest-neighbour dot separation1. Contrast and numerosity were modulated either separately in different blocks of trials, or together. If together, contrast and numerosity modulations could be either in register or in opposite spatial phase. The axis of spatial modulation was either the clockwise or anticlockwise diagonal; the observer's task was report which. Threshold modulation depth was measured by an adaptive procedure. Strong phase-dependent additivity between contrast and numerosity was found, suggestive of a mechanism detecting contrast energy modulation indifferently between numerosity and contrast. The implications for models of approxiate numerosity perception3 will be discussed. (1) Mulligan, J. B. & MacLeod, D. I. Reciprocity between luminance and dot density in the perception of brightness. Vision Res 28, 503-519 (1988). (2) Morgan, M. J. & Watt, R. J. Mechanisms of interpolation in human spatial vision. Nature 299, 553-555 (1982). (3) Burr, D. & Ross, J. A visual sense of number. Curr Biol 18, 425-428,
Meeting abstract presented at VSS 2014
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