POSTATTENTIVE VISION

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DESCRIPTION (Applicant's Abstract): The first steps in the perception of a novel scene can be described by a two-stage model with preattentive and attentive representations of visual stimuli. First, preattentive processes begin to analyze basic feature information at all locations. Prior research suggests that this involves the parallel processing of about a dozen basic features (color, size, etc.). Other tasks like object recognition of reading can be performed only with attention to the specific objects. The central question of this proposal is: What happens to the visual representation of an object after attention moves away? An observer looks at a fruit bowl. Preattentively, the stimulus is represented as a collection of colors, shapes, etc. With attention, the observer identifies bananas or grapes. Next, while viewing the same scene, the observer attends elsewhere. What is the nature of the post-attentive visual representation of the fruit? Do the effects of attention persist or does the visual representation revert to its preattentive state? Though post-attentive vision has received little study, it is central to an understanding of perception because, during sustained viewing of a scene, most visual experience must be post attentive. Post-attentive vision can be studied with several experimental methods: One is the repeated search paradigm in which a single search display is searched several times. For example, the letters "D, K, V & U" might appear on the screen. A probe letter would appear and the observer would respond "yes" if it were D, K, V or U or "no" if it were not. In repeated search, an observer searches a single display several times for different targets. Pilot experiments find little or no change in response time as a function of repeated search. This is a striking result because it suggests that repeated deployments of attention do not alter the visual representation in any way that can aid subsequent search. In a second, curve tracing paradigm, Ss must determine if two dots lie on the same of different curves. Reaction time in this task is dependent on the distance along the curve between the dots. As in repeated search, repeated curve tracing of the same curves does not improve performance. These and other results can be understood in the context of an "inattentional amnesia" hypothesis that holds that the visual representation has no memory. What is seen is seen in the present tense. Four lines of experiments are proposed to test the inattentional amnesia hypothesis and to expand the empirical basis for the study of post-attentive vision. These are studies of 1) basic properties of repeated search, 2) basic properties of repeated curve tracing, 3) the relationship of post-attentive vision and memory, and 4) the persistent effects of attention.