Differential contributions of circular and elongated spatial filters to the Café Wall illusion

The Café Wall illusion is induced in part by the spatial filtering properties of circular-symmetric receptive fields at the retina, and in part by cortical processes, presumably that have elongated receptive fields. Two experiments are reported that address these two contributions. The first shows a reversal effect that is consistent with brightness-induction and related theories. The second shows extinction of the effect in a manner predicted by recent observations of gating nonlinearity in cortical cells.