Masters Theses

Date of Award

8-2025

Degree Type

Thesis

Degree Name

Master of Arts

Major

Psychology

Major Professor

A. Caglar Tas

Committee Members

A. Caglar Tas, Aaron T. Buss, David W. Sutterer

Abstract

Saccadic suppression is a transient reduction in visual sensitivity around saccades that helps maintain perceptual stability by minimizing the disruptive blur caused by rapid eye movements. While previous studies have shown that undetected flashes during saccades can still bias later visual judgments, how these suppressed stimuli might alter the subsequent perception of brightness of a saccade target remains underexplored. In this study, 8 participants (reduced from an initial 10 due to exclusion criteria) with normal or corrected-to-normal vision completed a total of 512 trials in a dimly lit room. In the saccade condition, participants made a 15° rightward eye movement toward a colored target while a ~10ms luminance flash was presented either 15ms or 25ms after saccade onset. In the fixation condition, participants maintained gaze on a fixation point while viewing the same target-flash sequence. After each trial, participants reported the target’s color from a predefined spectrum and indicated whether they detected a flash. Our repeated-measures ANOVA revealed that color category significantly modulated flash effects: late flashes induced notably larger color-report deviations in green and cyan, while high-luminance flashes disproportionately affected green, cyan, and purple targets. In contrast, there were no robust overall main effects of flash timing or luminance alone. These findings indicate that even brief, often undetected flashes selectively bias post-saccadic luminance judgments for certain hues. By demonstrating that suppressed luminance flashes “leak” into subsequent perception, this study provides new insight into the boundaries of saccadic suppression. These results support the view that saccadic suppression acts more like a dynamic filter, strong for low-level magnocellular signals yet partially permeable for color-specific information, thereby maintaining perceptual stability while still allowing some transient visual input to shape the final percept.

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