The detectability of an object in our visual environment is primarily determined by the object's low-level visual salience, resulting from the physical characteristics of the object and its surroundings. In the present study we demonstrate that object detectability is additionally influenced by internally generated expectations about object properties, and that these influences are mediated by changes in perceptual sensitivity. Using continuous flash suppression (CFS) to render objects invisible, we found that providing valid information about the category membership of the object (e.g., "car") before stimulus presentation facilitated awareness of the object, as shown by improved localization performance relative to a noninformative baseline condition and to a condition with invalid prior information. Experiments 2 and 3 showed that the effect of expectation on detection generalized to binocular viewing conditions, with valid category cues facilitating the localization and detection of briefly presented objects. Experiment 4 extended these results to simple stimuli (oriented Gabor patches), for which valid orientation information improved localization performance. Finally, in Experiment 5 we found that the effect of expectation on detection and localization performance partly reflects increased perceptual sensitivity, as evidenced by decreased contrast detection thresholds for validly cued stimuli relative to noncued and invalidly cued stimuli. Together, these findings demonstrate that prior information about specific object properties dynamically enhances the effective signal of visual input matching the expected content, thereby biasing object detection in favor of expected objects.
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