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Tómas Kristjánsson, Ian Thornton, Árni Kristjánsson; Visual foraging with two simultaneous visual working memory templates. Journal of Vision 2017;17(10):1126. doi: 10.1167/17.10.1126.
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A key assumption in the literature on visual attention is that templates, corresponding to targets, are actively maintained in visual working memory (VWM) during visual search. Guiding visual attention is in fact often considered one of the main functions of VWM. According to a recent influential theory, only one search template can be active within visual working memory at any given time, while other templates have the status of accessory templates – they are accessible, but do not interact with visual attention. This account makes the clear prediction that switch-costs should always occur when targets change between attention deployments. An alternative account argues against this, claiming that more than one search template can be active at the same time and that the number of active templates is determined by attentional load rather than a precise number of templates. Using a novel iPad foraging task, where participants search for multiple targets from two categories, we measured the effects of switching between two categories. During foraging for disks of two colors among distractor disks of two different colors (feature foraging), observers quickly switched between simple target categories. Conversely, switch costs were an order of magnitude larger when the targets were distinguished by conjunctions of features. Rapid, effortless switching between target categories during feature foraging casts serious doubt on the claim that only a single search template can be active at any given time. While it is possible that the results reflect rapid alternations of a single active template, there is evidence that such template switching should take ~150-200 ms while switch costs during feature foraging were only between 20 and 40 ms. Overall, the results accord well with load theories while single-template accounts of VWM cannot satisfactorily explain the findings.
Meeting abstract presented at VSS 2017
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