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Rufin VanRullen, Christof Koch; Competition and selection during visual processing of natural scenes and objects. Journal of Vision 2003;3(1):8. doi: 10.1167/3.1.8.
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© ARVO (1962-2015); The Authors (2016-present)
When a visual scene, containing many discrete objects, is presented to our retinae, only a subset of these objects will be explicitly represented in visual awareness. The number of objects accessing short-term visual memory might be even smaller. Finally, it is not known to what extent “ignored” objects (those that do not enter visual awareness) will be processed —or recognized. By combining free recall, forced-choice recognition and visual priming paradigms for the same natural visual scenes and subjects, we were able to estimate these numbers, and provide insights as to the fate of objects that are not explicitly recognized in a single fixation. When presented for 250 ms with a scene containing 10 distinct objects, human observers can remember up to 4 objects with full confidence, and between 2 and 3 more when forced to guess. Importantly, the objects that the subjects consistently failed to report elicited a significant negative priming effect when presented in a subsequent task, suggesting that their identity was represented in high-level cortical areas of the visual system, before the corresponding neural activity was suppressed during attentional selection. These results shed light on neural mechanisms of attentional competition, and representational capacity at different levels of the human visual system.
Average number of objects selected in each scene, during the free recognition and the forced-choice recognition tasks, for test and control subjects. The number of remaining elements to choose from is indicated in parenthesis where applicable. Correction for guessing is calculated as described in the Methods. Standard deviation is indicated below each number. d′ is also provided for information.
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