Abstract
Models of basic visual processing typicaqlly neglect the role of the pupils: Dilated pupils increase the intake of light, resulting in a better signal-to-noise ratio. This should in turn facilitate detection performance in the visual periphery. In Experiment 1, we investigated performance of detecting a black spot on a grey cricle when the outer parts of the screen were either dark (causing large pupils) or bright (decreasing pupil sizes). In this online experiment, detection rates for the targets were in fact higher with irrelevant dark background than with a bright one. These findings were replicated in the laboratory under controlled lightning conditions while measuring the pupil size. In addition to current pupil size, its size during the preceding trial predicts performance. This indicates that in addition to the absolute pupil size, also the pupillary dynamics modulates perceptual functions.