Eye test - answer.

How many? Three?

Wrong, there are six - no joke!

Read again!

FINISHED FILES ARE THE
RESULT OF YEARS OF SCIENTIFIC
STUDY COMBINED WITH
THE EXPERIENCE OF YEARS

The reasoning is that the brain cannot process the word "OF".
Incredible or what?
Anyone who counts all six F's on the first go is a genius.
Three is normal.

Thanks to Heather Butters for this one

It certainly caught me out - and I knew the answer!