Try to count the “f”s in the text below:
How many did you find?
There are in fact six letter “f”s, even though most people will only find three. Why is this the case? It appears the brain has trouble processing the word “of”. The letter “f” generally makes the ‘f” sound, like in the word foal. With the word “of” though, the sound is more of a “v”. The result is that the brain completely misses the word “of” as it scans for the sound of “f”!