Progress in Machines and Systems Anka Slana Ozimic 8 1 2019 http://www.dline.info/pms/fulltext/v8n1/pmsv8n1_2.pdf The capacity of working memory to maintain visual information is highly limited and varies significantly across individuals. An important research effort is to understand the mechanisms of its limitation, one being the efficient selection of the relevant items from the immediate external environment to encode and maintain in working memory stores, while preventing the irrelevant items to occupy it’s capacity. Recently, a series of EEG studies using lateralized change detection task, in which the participants only have to maintain items presented on one visual hemifield, while irrelevant items are also presented on the opposite hemifield, identified a neurophysiological correlate of storage capacity in the form of contralateral delay activity (CDA) wave. Moreover, studies revealed that low-capacity participants maintain irrelevant items along the target items, when both are presented in the same visual hemifield, indicating a reduced ability to filter irrelevant stimuli from visual working memory. These studies, however, do not consider the possibility that participants might also maintain the irrelevant items presented to the opposite visual hemifield. To address this concern, we designed an experiment in which we directly manipulated the presence of distractors in the irrelevant visual hemifield to estimate and control for their effect. Twenty-eight participants took part in a visual working memory experiment in which they were asked to maintain orientation of items presented to the left or right visual hemifield, while the distracting items were either present or absent in the opposite visual hemifield. The results revealed significantly lower estimates of the capacity in the presence vs. absence of distractors, suggesting that participants were not able to ignore the distracting items presented to the opposite visual hemifield, challenging the validity of the estimates of visual working memory capacity in CDA and other studies employing lateralized change detection task.