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Roy Luria, Ed Vogel; Shape and color conjunction stimuli are represented as bound objects in visual working memory. Journal of Vision 2011;11(11):1290. doi: 10.1167/11.11.1290.
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© ARVO (1962-2015); The Authors (2016-present)
The integrated object view of visual working memory (WM) argues that objects (rather than features) are the building block of visual WM, so that adding an extra feature to an object does not result in any extra cost to WM capacity (Luck & Vogel, 1997). However, the integrated object account has been challenged on the basis of two primary grounds. First, it was argued that this view could not explain how binding of features in visual WM could scale up to maintain much more complex objects (Alvarez & Cavanah, 2004). Second, a number of studies have argued that objects that are composed of features from the same dimension (e.g., two colors) are not bound as one object in WM (Delvenne & Bruyer, 2004; Wheeler & Treisman, 2002). This led some to argue for a “weak” object view of visual WM (Olson & Jiang, 2002). The main problem with accepting the weak object hypothesis is that poor performance for multiple-feature objects could also be attributed to failures at other stages of processing of the change detection task rather than WM storage capacity. In the current study, we used the contralateral delay activity (the CDA) as an electrophysiological marker of WM capacity, to test those alternative hypotheses to the integrated object account. In two experiments we presented complex stimuli and color-color conjunction stimuli, and compared performance in displays that had one object but varying degrees of feature complexity. The results supported the integrated object account by showing that the CDA amplitude corresponded to the number of objects regardless of the number of features within each object, even for complex objects (such as random polygons) or color-color conjunction stimuli.
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