"Alzheimers' Eye Test" joke

Alzheimers' Eye Test
Count every " F " in the following text:

FINISHED FILES ARE THE RE
SULT OF YEARS OF SCIENTI
FIC STUDY COMBINED WITH
THE EXPERIENCE OF YEARS...
How many " Fs " really?
Don't scroll down yet. Count the " Fs ".

Wrong! There are 6 -- no joke. READ IT AGAIN!
Go Back and try to find the 6 F's before I give you the next clue..

OK, now the hidden part.
The brain cannot process " OF ".
Incredible or what? Go back and look again!!
Anyone who counts all 6 "F's" on the first go is a genius.
Three is normal, four is quite rare.
I got a three on first count.