Visual search following explicit or implicit category rule training

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Poor visual search performance affects the quality of life for many people with vision impairments, visual field loss (foveal or peripheral) and other low vision issues. Search involves multiple underlying neural processes including the guidance of attention to and subsequent categorization of stimuli, which necessarily rely on peripheral and foveal vision respectively. Our central hypothesis is that differences between central and peripheral vision will result in systematic disassociations between categorical search guidance (directing attention) and categorization. In recent years, the search literature has begun to explore categorical search, however, this work is still in its infancy. By bridging the search and categorization literatures, we can begin to characterize how the underlying category representation affects search performance. A prominent categorization theory, called COVIS (for COmpetition between Verbal and Implicit Systems) posits that explicit (verbalizable) category rule learning is mediated by the prefrontal cortex, while implicit (nonverbalizable) rule learning is mediated by subcortical structures related to associative learning. Most categorical search has historically utilized natural categories, which likely engage both systems to varying degrees. We will utilize simple perceptual stimuli common to the categorization literature to isolate categorical search performance mediated by explicit and implicit systems. In addition, we will also characterize decisional influences like base-rates and payoffs on categorical search performance. This research in healthy young controls is a necessary first step to develop new avenues to train individuals suffering from low vision, visual field loss (i.e. central or peripheral vision loss) and those with various visual cognitive deficits. For example, training people with an explicit verbalizable rule (when appropriate, such as pointing out specific features that are easily attended in peripheral vision), may result in easier and faster visual search training. However, much of the classification in daily life is likely learned via implicit (nonverbal) means and thus performance based feedback training and gradual associative learning through repeated exposure may improve search and classification outcomes. In the proposed experiments, participants will perform implicit or explicit category rule learning followed by search in which eye movements will be monitored. The eye movements allow us to distinguish between changes in the ability to direct spatial attention to search targets (guidance) and categorization processes. By examining the contribution of separate learning systems in the brain to determine category membership, the effects of categorical variability, and decisional influences (base-rates and payoffs), we will systematically characterize what makes explicit and implicit categorical search inefficient.