New Delhi, Aug. 11 -- Put a grid in front of people, and most will see order. That is what makes this puzzle work. The image shows rows and rows of the number 858, repeated without variation. It looks neat and complete. If you glance and move on, you will miss the detail that breaks the pattern. The designer tweaked a single box. The change is subtle. One of the cells has the number 828 written instead of 858.

Also read: Optical illusion: Only those with 10/10 vision can read this hidden sentence in 22 seconds

Repetition is a shortcut. Your eyes skim repeating elements and your brain fills in what it expects to see. Mix in a uniform font and soft, alternating orange shading across the cells, and the job gets even easier for your automat...