Second-order Mach bands: Chromatic and achromatic

Achromatic second-order (contrast) Mach bands can be perceived near the contrast ramp between two contrast levels. In this study we show that a repertoire of chromatic second-order Mach bands is also clearly perceived, under equal-luminance conditions (minimum motion technique). The results show that chromatic and achromatic second-order stimuli yield significant perceived second-order Mach bands, with approximately the same relative magnitude. At high spatial frequencies the effect is more prominent for achromatic second-order Mach bands stimuli than for chromatic second-order stimuli. The effect of the chromatic second-order Mach bands is smaller for complementary pairs of colors than for non-complementary pairs of colors. We suggest that the effect of second-order Mach bands is an expression of the mechanism of second-order induction.