I know its old but its a laugh, don't cheat and put your answer in spoilers Read this sentence: FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS. Now count the F's is that sentence. Count them ONLY ONCE. Do not go back and count them again. Spoiler There are 6 F's in the sentence. One of average intelligence finds 3 of them. If you spotted 4, you're above average. To see 5 is rare. If you caught 6, you are a genius. There is no catch. Most people forget the OFs. The human brain tends to see them as Vs instead of F's.