The feeling of being dazzled is evoked by images consisting of an achromatic
uniform center, surrounded by regions with luminance gradients. As the
perceptual distinctness of the central region has been suggested to contribute
to the feeling of being dazzled, we examined the effects of a gap between the
central and surrounding regions on the feeling of being dazzled. The stimulus
comprised a disk with uniform luminance surrounded by an annulus, of which the
luminance was decreased from the inner boundary to the periphery. Three
luminance profiles (linear, logistic, and inverse-logistic) of the surrounding
luminance ramps were used. The distinctness of the disk decreased in the order
of logistic, linear, and inverse-logistic profiles. The luminance of the disk,
the maximum luminance of the annulus, and the gap size were also varied. When
the luminance continuously transitioned from the disk to the annulus, the
feeling of being dazzled was stronger for the inverse-logistic annulus luminance
profile, compared with the logistic and linear profiles without a gap; however,
it was not different for the three profiles with a gap. Further, the feeling of
being dazzled increased when a gap was introduced for the logistic and linear
profiles, but not for the inverse-logistic profile. These results suggest that
the feeling of being dazzled was reduced by the perceptual indistinctness of the
central disk for the logistic and linear annulus luminance profiles, while the
gap restored the feeling of being dazzled by making the central disk
perceptually distinct.