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R. VanRullen, C. Koch; The capacity of visual awareness. Journal of Vision 2001;1(3):209. doi: 10.1167/1.3.209.
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© ARVO (1962-2015); The Authors (2016-present)
Change blindness experiments suggest that we are generally not aware of the entire visual scene. Rather, our conscious experience relies on information gathered across multiple fixations. It is not known, however, how much information can access visual awareness after one single fixation. This is because verbal report, a widely used measure of awareness contents, is subject to memory limitations: an element that reached awareness can be “forgotten” before the report. Therefore, verbal report only determines a lower-limit on the contents of visual awareness. Conversely, a great deal of visual information can access a high-level representation without entering awareness. Assessing the number of objects that reach a high-level, semantic visual representation (e.g. by measuring semantic priming), constitutes an upper-limit on the contents of visual awareness. We presented our subjects with brief, masked natural scenes containing, on average, 10 different objects. After each scene, subjects reported the name (chosen from a list) and properties (size, location) of the objects they had seen. Immediately following this report sequence, a priming sequence was run. A target name was presented, followed by an object. Subjects responded when the object matched the target name. Objects from the previous target scene were presented among other “new” objects. A statistical analysis of reaction times obtained for “previously viewed” and “new” objects reveals the number of primed objects in each image. By simply combining verbal report and semantic priming measures, for the same subjects and visual scenes, it becomes possible to characterize the capacity of visual awareness.
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