This is a quite interesting "IQ-test". 
It's very short so try it, you may be amazed. 
There are no tricks to the test. 

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.

Here is the correct answer.