Detecting and remembering pictures with and without visual noise.

Objects in a scene are often partially occluded without causing the viewer any problem: the occluded parts are apparently represented via amodal completion. To evaluate human ability to perceive and remember partially occluded pictures, we showed sequences of pictures using rapid serial visual presentation (RSVP) for durations of 53 ms, 107 ms, 213 ms, or 426 ms/picture. Participants either attempted to detect a named target (e.g., "businessmen at table") or were given a yes-no recognition memory test of one item. In Experiment 1, with as much as 30% of the picture area covered, detection and recognition were both well above chance. More interestingly, occlusion significantly affected recognition memory but not target detection. In Experiment 2, when pictures were inverted, occlusion impaired detection as severely as recognition. For target detection, the interaction between occlusion and inversion was significant. By contrast, taking away color information did not significantly reduce detection's tolerance of occlusion (Experiment 3). Finally, Experiment 4 showed that with 40% of the picture area occluded, detection performance was impaired. These results support the hypothesis that contextual gist information facilitates visual processes that tolerate occluding noise. Although inversion and color were tested in particular, the presented paradigm can also be used to investigate the role of other factors in gist representation.