Appearance of an illusory object in the blind spot

We report a phenomenon showing new aspects of perceptual filling-in at the blind spot. When two and three discs were presented below the blind spot, observers perceived them as three and four discs, respectively, but when they were presented in the nasal visual field as a control, the perceived numbers were veridical. The phenomenon demonstrates that the visual system produces an illusory object in the blind spot even when the inducing objects presented on only one side of the blind spot are clearly discrete and countable.