Abstract
The glare illusion is a pictorial representation where one perceives self-luminosity in the absence of physical luminance. Several pupillometry studies have investigated such illusory brightness enhancement in terms of automatic, physiological, responses and shown that the enhanced brightness perception can be reflected in pupil constrictions to the illusory light, despite there is no corresponding physical luminance change. However, an illusory brightness enhancement occurs also with ''white'' or "gray'' patches in the central region of the glare illusion and not only in the perceptual mode of ''self-luminosity'' (Tamura et al., 2017). Thus, we aimed to explore what factor contributes to the pupil constriction according to these two aspects of illusory perception with a pupillometry experiment where participants observed either as a colored glare illusion, which had color-inducer in the peripheral gradient region, or as a control condition which inverted the gradients, so as to manipulate the perceived brightness while keeping equiluminance across conditions (Experiment1a). We confirmed the presence of brightness enhancement, dependent on the color-inducer, using a method of adjustment (Experiment1b). Although the amount of pupil constriction was significantly correlated with the perceived brightness in each colored glare illusion, the differences in pupil constrictions between glare and control stimuli were similar across the color conditions (n=16). Subsequently, we also conducted an experiment probing the level of luminosity perception, by using glare illusions with varied angle of the gradients to affect the participants' perceptual mode from 'white' to 'luminous' (Experiment2). The results showed that pupillary constriction was increased only when the participants reported a feeling of luminosity from the glare illusion (n=13). These findings suggest that although the pupillary constriction indeed reflects enhanced brightness of the glare illusion, it does also reflect a perceptual mode of luminosity.
Meeting abstract presented at VSS 2018