Abstract Perceived segregation between element-arrangement textures is affected both by spatial scab and background luminance. The effects on the spatial nonlinearity are consistent with the proposed structure for complex (second-order) channels. The effects on the intensive nonlinearity a not consistent with an early, local nonlinearity but are consistent with either (i) a relatively early, local, nonlinearity occurring before the spatial frequency channels but after a sensitivity-setting sta e, or (ii) inhibitory interaction among channels modeled as a normalization network. Thus the to ture intensive nonlinearity comes after sensitivity to spatial frequency and background luminance has been determined. For six of seven observers, the texture intensive nonlinearity was compress' e by 10% contrast for both increments and decrements (at high background luminance, large s atial scale).