Abstract

Efficient visual search requires prioritizing relevant information while suppressing salient but irrelevant distractors that compete for attention. Previous studies have shown that attentional suppression of salient distractors can be modulated by perceptual grouping (Ma & Abrams, 2023) and distractor salience (Stilwell et al., 2023; 2024). However, prior work has relied primarily on discrete keypress or oculomotor measures, such as reaction time, accuracy, and first saccadic destination. Although these measures provide important evidence about whether distractors interfere with or are suppressed during visual search, it still remains unclear how distractor-induced spatial biases emerge and change over the course of the target selection. The present dissertation examined this question by using target-directed reaching movements. Across four experiments, participants performed a visual search task in which they searched for a specific target shape among heterogeneous non-target shapes and moved a mouse cursor to click the target, sometimes while in the presence of a salient distractor. Experiments 1 and 2 examined how previously observed effects of perceptual grouping on distractor suppression are reflected in the movements. Experiment 1 used rectangular frames to induce common-region grouping, whereas Experiment 2 used connecting lines to induce relational connectedness without enclosing the stimuli within boundary structures. The findings showed that the extent to which grouping-based suppression effects were reflected in reaching movements depended on the type of grouping cue. Common-region frames provided limited evidence that grouping-based suppression was reflected in reaching movements, likely because the frames also introduced spatial constraints that could influence the movement path. In contrast, connecting lines led to strong trajectory repulsion away from the distractor when the target and distractor were grouped together. This finding suggests that the grouping benefit is not limited to faster response selection, but can also be reflected as a spatial bias away from the distractor during reaching, providing new insight into the effects of perceptual grouping on attentional suppression. Experiments 3 and 4 used reaching movements to extend prior work on salience effects on attentional suppression by testing whether these effects are also reflected in the timing and spatial trajectory of target selection. Experiment 3 showed that when salience was defined by color contrast, high-salience distractors elicited stronger suppression than low-salience distractors in both the timing of reaching and greater trajectory deviations away from the distractor. This finding suggests that salience-based suppression is not a discrete process, but instead unfolds over time during target selection. Experiment 4 tested whether the same pattern could generalize to a different salience manipulation, color-fill status. In this case, distractor salience influenced the overall response duration, but did not produce reliable evidence of suppression in the movement trajectory. Together, the results show that distractor suppression unfolds dynamically over time as the target is selected during visual search. By measuring reaching movements, the present dissertation provides evidence that during search, salient distractors are actively suppressed or avoided, rather than simply failing to capture attention. The findings also show that reaching movements can serve as a sensitive measure of how attentional control is deployed during visual search.

Committee Chair

Richard Abrams

Committee Members

Ian Dobbins; Julie Bugg; Weiwei Zhang; Wouter Kool

Degree

Doctor of Philosophy (PhD)

Author's Department

Psychology

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

8-17-2026

Language

English (en)

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Psychology Commons

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