Finished files are the result of years of scientific study combined withthe experience of years.
Read the sentence once, out loud or in your head. Then write your count.
No re-reading, no pointing with your finger. First count = locked in.
The answer is 6 — and almost everyone says 3
There are six F's. Most people count three. The brain skips the F's hiding inside 'of' — three of them — because 'of' is pronounced with a V-sound. Your eyes see it, your brain airbrushes it out.
This is attention blindness: you don't see with your eyes, you see with your expectations. Great readers are the WORST at this puzzle. Spotting your own blind spot once? That's the whole lesson.