Pupil size correlates with near-threshold detection performance irrespective of stimulus color, eccentricity, or retinal adaptation state.

In visual near-threshold detection tasks, larger prestimulus pupil size is associated with improved accuracy. However, previous studies have used black-and-white peripherally presented stimuli, leaving open the question of whether the relationship persists when targets differ in their color or eccentricity. Here, we addressed this question with three experiments that systematically varied the lighting conditions and target properties in a visual near-threshold detection task (data collected in 2022-2024). Light conditions ranged from dark to dim to bright, with the dark condition including a period of dark adaptation. Possible target colors were blue and red on a black background (dark condition), blue and red on a gray background (dim condition), or yellow and cyan on a white background (bright condition). Possible target eccentricities ranged from parafoveal to peripheral, in a continuous manner (Experiment 3) or as two predefined near and far eccentricities (Experiments 1 and 2). Across all experiments, we show that larger prestimulus pupil size is associated with improved performance. This large-pupil advantage is not systematically modulated by the color or eccentricity of the targets, the illumination of the testing room, or the retinal adaptation state. We conclude that the phenomenon is robust, indicating that pupil size affects vision in a behaviorally relevant manner, regardless of the exact conditions. (PsycInfo Database Record (c) 2026 APA, all rights reserved).