Competition in visual working memory for control of search

Recent perspectives on selective attention posit a central role for visual working memory (VWM) in the top-down control of attention. According to the biased-competition model (Desimone & Duncan, 1995), active maintenance of an object in VWM gives matching (Downing, 2000) or related (Moores, Laiti, & Chelazzi, 2003) objects in the environment a competitive advantage over other objects in gaining access to limited processing resources. Participants in this study performed a visual search task while simultaneously maintaining a second item in VWM. On half of the trials, this item appeared as a distractor item in the search array. We found no evidence that this item interferes with successful selection of the search target, as measured with response time in a target detection task and accuracy in a target discrimination task. These results are consistent with two general models: One in which a representation of the current task biases the competition between items in a unitary VWM, or one in which VWM is fractionated to allow for maintenance of critical items that are not immediately relevant to the task.