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Student
Title
Supervisor
Faculty
Educational Programme
Final Grade
Year of Graduation
Kirill Kozlov
Role of Working Memory and Perceptual Similarity in Dual-target Visual Search
2019
Subsequent search misses (SSM) is a decrease in accuracy at finding the second target after the successful detection of the first one. Three different theories have been proposed to explain the causes of the SSM: satisfaction of search account (after detection of the first target person immediately stops subsequent search even if search field could include another target, because he is satisfied), perceptual set account (when the first target is detected, people will be biased to search for an object that is similar to the first one), resource deployment account (a person will spend a certain amount of limited cognitive resources to find the first target, and, consequently, the will be less resources to find the second target).

Target-target perceptual similarity was found to decrease the magnitude of SSM, while working memory load (e.g. memory for found targets) increases it. We wanted to find out whether both of these factors work together or separately. Thus, we used a combined visual search and working memory task, when the participant had to perform visual search task while holding the stimuli from memory task in working memory. Stimuli for both tasks were rectangles with gaps. Each trial could contain two, one or no targets. In case of two targets, they could have 0, 1 or 2 shared features. Repeated measures ANOVA was used to analyze accuracy and reaction time. Perceptually similar targets were found more accurate and faster than perceptually dissimilar ones. There was no effect of WM load on SSM magnitude. Also there wasn't significant interaction between WM load and perceptual similarity, assuming different mechanisms responsible for perceptual similarity and working memory load factors in SSM errors.

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