We report here that shape-from-shading stimuli evoked a long-latency contextual pop-out response in V1 and V2 neurons of macaque monkeys, particularly after the monkeys had used the stimuli in a behavioral task. The magnitudes of the pop-out responses were correlated to the monkeys' behavioral performance, suggesting that these signals are neural correlates of perceptual pop-out saliency. The signals changed with the animal's behavioral adaptation to stimulus contingencies, indicating that perceptual saliency is also a function of experience and behavioral relevance. The evidence that higher-order stimulus attributes and task experience can influence early visual processing supports the notion that perceptual computation is an interactive and plastic process involving multiple cortical areas.