In order to effectively search the visual environment, an observer must continually locate objects of interest amid an abundance of irrelevant and distracting stimuli. These visual distractors can sometimes inadvertently attract attention to their locations, even when an observer is attempting to search for an entirely different object. To deal with visual distractors, it has been well established that the visual system can implement a suppression mechanism to filter out irrelevant stimuli. Within the past decade, event-related potential (ERP) recordings have isolated an attentional component that is thought to reflect this suppressive processing. This ERP component—termed the distractor positivity (PD)—has been used to demonstrate that the sensory processing of irrelevant information can be strongly modulated in line with the visual search goals of an observer. Here, four electrophysiological studies of attention are presented which focus on yielding insight into how the visual system deals with irrelevant information during visual search and seeks to further our understanding of the PD component. Chapter 2 tests the stimulus conditions necessary to elicit the distractor suppression indexed by the PD by examining how differences in the salience of an irrelevant stimuli affect visual search. Chapter 3 explores how individual differences in target and distractor processing are associated with variations in visual working memory (vWM) capacity. Chapter 4 asks how distractor processing is altered during a disruption of attentional control by examining how visual search is affected during the attentional blink (AB). Chapter 5 explores how high levels of trait anxiety alter inhibitory control and the ability to ignore distracting information. In the final chapter, future directions are discussed and a model for attentional processing is proposed.
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Thesis advisor: McDonald, John J.
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