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Alice R. Shapiro, Arthur G. Shapiro; A multiscale filtering model can explain brightness motion in single-field contrast asynchronies. Journal of Vision 2006;6(6):713. doi: 10.1167/6.6.713.
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© ARVO (1962-2015); The Authors (2016-present)
In simultaneous contrast demonstrations, two physically identical patches of light have different brightness levels when placed in different contexts. One current model of such phenomena is based on multiscale filtering of the visual image. Here, we use a single-field contrast asynchrony to test for the presence of multiscale spatial channels in brightness perception (“the barbell illusion”—see Journalofvision.org/10/5/2, figure 11b). The stimulus consists of a rectangular field, with one short end positioned next to a light field, and the other next to a dark field. As the luminance of the rectangle modulates in time, a veil of brightness appears to move back and forth across the rectangle (brightness motion). We present a model based on an array of rectified center-surround filters applied over time (in a X,t plot, the maximal filtered response drifts in synchrony with the brightness motion). The model predicts that if inner fields of opposite contrast are placed between the flanking fields and the modulating rectangle, then filters of different scales will produce motion in opposite directions. In our experiments, a small dot drifts back and forth along the length of the modulating rectangle. The observer adjusts the phase of the dot so that it matches the phase of the brightness motion. We manipulate contrast and size of the inner and outer flanks. We find that when the inner flanks are thin and of low contrast, the phase of brightness motion is determined by the contrast of the outer flanks, therefore supporting a multiscale model.
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