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Edward K. Vogel, Akiko Ikkai, Veronica Perez; Do perceptually challenging objects consume more working memory capacity?. Journal of Vision 2006;6(6):34. doi: 10.1167/6.6.34.
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© ARVO (1962-2015); The Authors (2016-present)
Visual working memory (VWM) is well known to be highly capacity-limited, typically estimated to be approximately 3 simple objects. Here we examined whether this capacity is best expressed in terms of the number of items or the perceptual requirements of the memory items. To do this we examined an ERP correlate of maintenance in VWM while subjects performed a memory task with items that were either perceptually demanding or posed minimal perceptual requirements. The amplitude of the Contralateral delay activity (CDA) has previously been shown to be strongly modulated by the number of items currently held in memory. In this study, we examined whether the amplitude of this activity would be modulated by the perceptual requirements of the memory items, irrespective of the number of items in the display. We manipulated the luminance of the memory items (bright vs. dim) as well as set size (2 items vs. 4 items) in a standard VWM task. Behaviorally, performance was significantly impaired on the perceptually-challenging dim trials as compared to the bright items. However, despite this increase in the perceptual demands for the dim memory items, CDA amplitude was not modulated by the perceptual requirements imposed by the items in the display but was primarily sensitive to the number of items in the display. These results support models that propose that the number of items and not the properties of the items primarily determines the capacity of visual working memory.
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