India, Aug. 30 -- Optical illusions continue to draw people in, and a new one is garnering plenty of attention. At first glance, the picture appears very ordinary, consisting of a large block of numbers, with the digit 6 repeated in rows and columns. But hidden inside the grid is one different number, a 9, and the task is to find it.

The trick here is that your eyes get used to the pattern right away. Once the brain sees row after row of the same figure, it stops searching for anything unusual. That is why the odd number blends in so easily. Many people stare at the screen for a long time before they even realize where it is.

Illusions like this have turned into a bit of a trend online. They are shared widely because people enjoy testin...