Citation

Zavagno D, Tommasi L, Laeng B. Iperception 2017; 8(4): e2041669517717754.

Affiliation

Department of Psychology, University of Oslo, Norway.

Copyright

(Copyright © 2017, SAGE Publishing)

DOI

10.1177/2041669517717754

PMID

28835810

PMCID

PMC5555513

Abstract

Pupil diameters were recorded with an eye-tracker while participants observed cruciform patterns of gray-scale gradients that evoked illusions of enhanced brightness (glare) or of enhanced darkness. The illusions were either presented as static images or as dynamic animations which initially appeared as a pattern of filled squares that-in a few seconds-gradually changed into gradients until the patterns were identical to the static ones. Gradients could either converge toward the center, resulting in a central region of enhanced, illusory, brightness or darkness, or oriented toward each side of the screen, resulting in the perception of a peripheral ring of illusory brightness or darkness. It was found that pupil responses to these illusions matched both the direction and intensity of perceived changes in light: Glare stimuli resulted in pupil constrictions, and darkness stimuli evoked dilations of the pupils. A second experiment found that gradients of brightness were most effective in constricting the pupils than isoluminant step-luminance, local, variations in luminance. This set of findings suggest that the eye strategically adjusts to reflect in a predictive manner, given that these brightness illusions only suggest a change in luminance when none has occurred, the content within brightness maps of the visual scene.

Language: en

Keywords

brightness; eye pupil; illusion; luminance; pupillometry