Illusory brightness step in the Chevreul illusion

Vision Research
M C MorroneJ Ross


It is well known that a staircase luminance profile is not seen veridically, but appears as the scallopy-like Chevreul illusion. We have shown that adding thin lines (either light or dark) to the centre of each step creates an illusory brightness change at the point of the line. The regions between the added lines and the edges seem to be uniform, with a clear change in brightness at the point where the line was added. The conditions under which the illusion occurred were measured systematically, both by contrast matching and by annulment. One model that can readily account for the illusion is the local-energy model of feature detection (Morrone & Burr, 1988 Proceedings of the Royal Society of London B, 235, 221-245). Adding the bar to the step creates a peak in local energy at all scales. At the higher scales, the phase of the energy is near zero, the signal for a line; but at the lower scales the phase is near pi/2, the signal for an edge. We propose that the edge signal of the lower scales causes the brightness illusion and that this brightness difference is structured by the feature defined sharply by the higher scales (even though that feature is not an edge). As well as predicting the existence of the illusion, simulation...Continue Reading


Jan 1, 1979·Vision Research·H R Wilson, J R Bergen
Aug 1, 1992·Vision Research·F Kingdom, B Moulden
Jan 1, 1991·Perception·P Bressan, G Vallortigara
Jan 1, 1989·Vision Research·J RossD C Burr
Dec 22, 1988·Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character·M C Morrone, D C Burr

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