There are no light-sensitive receptors on the retina where the optic nerve is. The creates a blind spot in the visual field. (Only vertebrate eyes have the oddity of an optic nerve creating a blind spot by running in front of the photoreceptors. Other animals, including cephalopods, do not have this design defect.) To prevent perceiving this gap, the mind fills in the blank space with inferred information from surrounding areas.
While this is usually accurate enough, it means that our perception in the blind spot is objectively unreliable. ~ German cognitive psychologist Benedikt Ehinger et al
An experiment to discern how the blind spot is filled in determined that people can prefer the imagined patch that the mind provides over actual sensory input.
Generated information is sometimes treated as more reliable than sensory information from the outside world. ~ Benedikt Ehinger et al