icipants were asked to identify a second feature of a color oddball in a visual search task,they showed faster responses when the distractor color was passively viewed than when the target color was previewed in the preceding oddball-absent trial.This inter-trial effect in visual search is referred to as the distractor previewing effect (DPE),and it reflects an attentional bias that keeps attention from focusing on features that had been recently inspected but failed to produce a target.The DPE has been observed with feature-based tasks as well as with category-based tasks.In the current study,we examined the DPE when participants were asked to search for a fear-relevant animal (snake or spider) among neutral distractors (horse or cat) or vice versa.That is,three pictures of animals appeared on each display,with or without one picture belonging to a different category from the other two.If a category oddball was found,participants identified whether a red dot was superimposed to the left or right of this oddball.The results showed that their responses were faster after they had previewed pictures of the distractor category than after they had previewed pictures of the target category in the preceding oddball-absent trial.These results confirmed the emergence of the category DPE with pictures,and suggested that participants were sensitive to trial history in processing of fear-relevant stimuli.The underlying mechanisms of this inter-trial effect were also discussed.