COMPARISON BETWEEN SPATIAL INTERACTIONS IN PERCEIVED CONTRAST AND PERCEIVED BRIGHTNESS

We examined the spatial integration of simultaneously induced achromat ic contrast and compared it to the spatial integration of simultaneous ly induced brightness. This study extends the work of Zaidi et al. [(1 992). Vision Research, 32, pp. 1695-1707], who showed that the total m agnitude of induced brightness can be described as the weighted sum of the brightness induced by individual elements of the surround. The re sults show that contrast induction, though weaker than brightness indu ction, occurs over greater distances, and that a weighted spatial summ ation model for contrast induction requires an additional static non-l inear 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. (C) 1997 Els evier Science Ltd.