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Michael Patterson, Wan Ting Low; Strategic Control of Visual Working Memory for Global and Local Features. Journal of Vision 2010;10(7):771. doi: 10.1167/10.7.771.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have demonstrated a bias to focus on global over local features in both visual attention and visual working memory. In two new studies, we created novel stimuli too complex to be remembered in every detail. We examined the effect of the varying presentation delays of post-stimulus instructions that directed participants to focus on global or local features. We predicted that instructions to focus on specific features would reduce working memory load, but at the cost of diminishing memory for other features of the stimulus. In study 1, participants viewed polygons made up of twenty lines which were grouped into four colors. The polygons were displayed for 1 sec, followed by a 0-4 sec delay. Next, instructions were given to focus on either a part (1/4 of the polygon), an object (1/2 of the polygon), or the whole polygon. After another 0-4 sec delay, participants selected between four images, only one of which matched the initial stimulus. Consistent with our previous research, instructions increased accuracy. However, instructions also influenced error types. Participants who had been instructed to focus on global features erroneously selected lures with a large change to only one part. Participants who had been instructed to focus on object-level properties erroneously selected lures with small changes to every part, yet kept the original global shape. In the second study, participants viewed Navon figures made up of polygons instead of letters. Lures contained either global changes, local changes, or both global and local changes. Instructions guided participants to focus on each of these levels. The presence of instructions lead to a decrease in performance if the instructions were shown immediately after the stimulus, indicating that visual information must be consolidated within working memory before strategic control of focus can occur.
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