Optical illusions are a maddeningly wonderful way to understand how brains compensate for what the limitations of what it is able to process. The above video from ASAP Science highlights a couple optical illusions that reveal how these processes work.
They lead with the below image. Close your left eye and stare at the cross, then move your head forward and backward. You'll find a point where the dot disappears into your blind spot.
This and other optical illusions are explained in the video, including the illusion below. Most people aren't capable of seeing all 12 dots in the image at once.
Optical illusions like these are scientifically useful for understanding how eyes and brains function. It highlights shortcomings like the blind spot in the above illusion or ways the brain fills in gaps of information filtered out in an attempt to work more efficiently.
The utility to illusions like these has been tidily shown in lists like the Neural Correlate Society's Optical Illusions of the Year, which comes with explanations about what the illusions reveal.
Watch ASAP Science's video above to get a better understanding of how these illusions work and see a few frustrating optical illusions.