Post-Attentive Vision

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DESCRIPTION (provided by applicant): This proposal addresses a fundamental tension in current work on vision, visual attention, & visual memory. On the one hand, we can recognize visual stimuli in a fraction of a second and, with slightly longer presentations, such stimuli can be remembered for days. On the other hand, phenomena like "change blindness" and "inattentional blindness" seem to show striking failures of visual representation and/or memory. Observers fail to report apparently obvious aspects of visual displays. In our own work on "postattentive vision" (the subject of the previous grant period), Ss searched repeatedly through static, unchanging displays. Hundreds of trials did not improve the efficiency of Repeated Search even though Ss had clearly memorized the display. The goal of the present proposal is to reconcile these disparate streams of research. How can an observer recognize a scene 24 hours after a one second presentation and yet be unaware if an object in that scene disintegrates before his eyes? There are three specific aims: Why do subjects choose vision over memory in Repeated Search? We will test three hypotheses about the cause of this apparent reliance on vision. A) Vision First: When available vision always takes priority, B) Inefficient Memory: Ss do, in fact, search memory but that search is as inefficient as visual search, or C) Pragmatic Choice: The costs, even of efficient memory search, make inefficient visual search worthwhile. When does memory contribute to visual search? In the "Contextual Cueing" paradigm of Chun and Jiang (1998), memory for repeated exposure to a search stimulus does aid subsequent search. We examine the relationship of Contextual Cueing to Repeated Search. We hypothesize that these are complementary, not contradictory findings. What is the gist of a picture? In Picture Memory tasks, Ss are said to remember the "gist" of an image. We propose that this gist includes the distribution of basic features like color and size and a rapid calculation of the structure or "spatial envelope" (Oliva & Torralba, 2001) of the scene. Gist also includes a limited number of attended objects. We will use several converging experimental paradigms to assess these components of the gist of a scene. Taken together, the results of this program of research will test hypotheses that tie our understanding of visual search to our understanding of short and longer term visual memory.