Comparison between Spatial Interactions in Perceived Contrast and Perceived Brightness

We examined the spatial integration of simultaneously induced achromatic contrast and compared it to the spatial integration of simultaneously induced brightness. This study extends the work of Zaidi et al. [(1992). Vision Research, 32, pp. 1695-1707], who showed that the total magnitude of induced brightness can be described as the weighted sum of the brightness induced by individual elements of the surround. The results show that contrast induction, though weaker than brightness induction, occurs over greater distances, and that a weighted spatial summation model for contrast induction requires an additional static non-linear compression, which is not required to model brightness induction. The analysis indicates that the contrast compression occurs prior to the lateral interactions that generate induced contrast.