India, Oct. 8 -- These optical illusion quizzes are among the most popular brain exercises online, having attracted many people on various social networking sites each week. These visual tests are entertaining but also provide a brief exercise for your mind. Cognitive psychologists reveal that the human mind can process visual stimuli in as little as 13 milliseconds, but it also takes mental shortcuts that could result in bizarre errors, and this is precisely what makes the recent viral challenge quite popular.

The challenge requires players to find the well-hidden number '46' that is buried amongst numerous '64's in just ten seconds. The puzzle might seem easy at first glance; however, due to the similar formation of digits, it proves t...