This is so cool.
Read this sentence:

FINISHED FILES ARE THE RE-
SULT OF YEARS OF SCIENTIF-
IC STUDY COMBINED WITH
THE EXPERIENCE OF YEARS.

Now count ALOUD the F's in that sentence. Count them ONLY ONCE: do not go 
back and count them again. See below...

ANSWER:

There are six F's in the sentence. One of average intelligence finds three 
of them. If you spotted four, you're above average. If you got five, you 
can turn your nose at most anybody. If you caught six, you are a genius.  
There is no catch.  Many people forget the "OF"'s.  The human brain tends 
to see them as V's and not F's. Pretty weird, huh?  It fools almost 
everybody.

Robert