Low-level features determine brightness in White's and Benary's illusions.

We masked White's and Benary's brightness illusions and simultaneous contrast with narrowband visual noise and measured detection thresholds and brightness. The noise was either isotropic or orientation filtered. A narrow spatial frequency tuning was found for detection and brightness for every stimulus. A narrow orientation tuning was also found: the strength of the illusions decreased (White and Benary) or increased (White) depending on the orientation of the mask. The critical borders were always of the same contrast polarity. The results suggest that the brightness in figure-ground scenes is determined by mechanisms integrating incremental and decremental borders in early visual cortices.