With your face level with the image and around a foot away:
- Cover your left eye.
- Look steadily at the cross with your right eye.
- Move slowly back and forth to the place where the spot disappears.
- Flick your eye between the cross and the spot to see the magic happen.
Why this matters
The blind-spot test demonstrates a simple truth – that reality is built in the brain. When the circle falls into the blind spot (caused by the optic nerve at the back of the eye) the brain simulates it’s best guess as to what should be there.
In this case, a simple whiteness.
See more Science of Storytelling.