This example baffles me. The results do not differ between native English speakers and those, who learned English later. I have not tried it with non-English speakers. When I find other examples, in other languages, perhaps I will understand what is happening.

Count the number of F's in the following text:

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

Managed it?

Scroll down only after you have counted them!

OK?

How many?

Three?

Wrong, there are six !

Read again!

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

It seems that the brain cannot process the word "OF".

Three is normal....why?