How many F's do you see in this sentence

There are 6. The trick is that the brain usually ignores "of"s because they're just connectors that don't really mean anything (I think).

Just pay very very close attention to the sentence as you read and you'll find all of them.

@Kalovale: No sex causes bad eyes? Oh really?

I can read that with a little difficulty...but I haven't had sex?