Spatial properties of scintillating grid illusion through visual experiments and numerical simulations

This study investigated the spatial properties of the scintillating grid illusion through three visual experiments and numerical simulations using differential equations. Experiment 1 was conducted to confirm that the scintillating grid illusion occurred in the peripheral vision under binocular viewing. The results showed that illusory blackness was perceived on the white disk at the horizontal viewing angles of +/- 6.0, +/- 9.0, and +/- 12.0 degrees stronger than +/- 0.6 and +/- 3.0 degrees. Experiment 2 investigated the area where the scintillating grid illusion occurred not only in the horizontal orientation but also in the vertical orientation. The results showed that the area of the scintillating grid illusion was farther from the fixation point in the horizontal orientation than in the vertical orientation under binocular viewing. Experiment 3 examined the spatial properties of the scintillating grid illusion under monocular viewing, revealing that the area of the scintillating grid illusion was wider in the horizontal orientation than in the vertical orientation. These results suggest that the scintillating grid illusion has spatial anisotropy, regardless of binocular or monocular viewing. Based on the findings in the visual experiments and electrophysiology, this study improved a mathematical model using differential equations for retinal information processing. The improved model demonstrated the results of numerical simulations similar to the spatial properties of the scintillating grid illusion under experimental results. The numerical simulations suggested that the blurring and inhibitory effects could be involved in the spatial properties of the scintillating grid illusion.