Here is a very simple exercise.
Count every ‘F’ in the following text. Count them ONLY ONCE and try to get it right.
Finished counting? Sure you got all the F’s ? Let’s find out if you found all of them.
There are 6 ‘F’s in the sentence. Don’t believe? Ok, count again if you want to.
Most people spot 3 ‘F’s. If you got 4 then you’re above average. To see 5 is very unusual. If you saw all six, you are remarkable.
Most people miss the ‘F’s in ‘OF’. When we read we tend to skip short words like ‘of’; our eyes don’t physically focus on them. Our brain ‘assumes’ their presence and fills in the gaps to make sense automatically.