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Maya Ankaoua, Roy Luria; Differences between online addition and subtraction in visual working memory. Journal of Vision 2020;20(11):722. doi: https://doi.org/10.1167/jov.20.11.722.
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Visual working memory (VWM) is responsible for both storage and processing of information. Nevertheless, most of previous research has focused on the maintenance part. While it has been shown that VWM devotes more capacity when maintaining more information, the current work investigated VWM capacity during mental subtraction and addition processes, while keeping the number of encoded objects constant.
In the addition experiment, two shapes were presented. In the maintenance condition, participants were asked to press a key when they finished encoding and maintaining both shapes. In the addition condition, participants had to combine the two shapes into one integrated shape and press a key when this addition process was completed. Then, another shape was presented and participants were asked to indicate whether it was similar to one of the two initial shapes in the maintenance condition, or similar to the outcome of the integrated shape in the addition condition. Similarly, in the subtraction experiment, participants were asked to either maintain two shapes, or to subtract one from the other and maintain the result. We collected EEG data and used the Contralateral Delay Activity (CDA) as an indicator of VWM involvement.
In both experiments, behavioral results showed that adding or subtracting was more difficult (longer RTs and lower accuracy rates) than just maintain the items. The CDA showed a higher amplitude both in the adding and subtracting conditions as compared to the maintenance condition. This suggests that while performing the addition or subtraction processes, more VWM is involved compared to when we simply maintain the same amount of information. This can be due to intermediate products we create and maintain while performing the addition or subtraction.
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