MACH-BAND ATTENUATION BY ADJACENT STIMULI - EXPERIMENT AND FILLING-INSIMULATIONS

Mach bands are illusory bright and dark bands seen where a luminance p lateau meets a ramp, as in half shadows or penumbras. It has previousl y been shown that Mach bands are attenuated by placing stimuli, such a s bars, nearby. It was shown in an experiment in which Mach-band atten uation for bar and Craik-O'Brien stimuli was compared that they are eq ually effective in attenuating Mach bands. The results suggest that th e abrupt luminance transition of a stimulus adjacent to a ramp is resp onsible for the attenuation. The findings are interpreted in terms of a recent filling-in model of brightness perception and the results of computer simulations of stimuli are shown.