Spatial comparison of disappearance and scintillation phenomena using a single-unit scintillating grid illusion

The scintillating grid illusion induces the phenomena of disappearance and scintillation. However, it is unclear in which peripheral region these phenomena occur. This study aimed to investigate the spatial properties of disappearance and scintillation phenomena in the scintillating grid illusion. In Experiment 1, participants binocularly observed a single-unit scintillating grid illusion and responded whether a white disk and illusory blackness were perceived. As a result, the perceptual region of the white disk was larger in the horizontal direction than in the vertical direction, as well as the perceptual region of the illusory blackness. This result indicates that both perceptual regions have spatial anisotropy. In Experiment 2, the same task as in Experiment 1 was performed with monocular viewing. The results did not exactly reject spatial anisotropy in monocular vision, regardless of the perceptual regions. This study may contribute to understanding how disappearance and scintillation phenomena coexist in the scintillating grid illusion.