You can hold a conversation with two phrases, consisting of four words. “I don’t know”, and “Indeed.”
With this, you can hold a conversation without having to think. Imagine a conversation on a plane. Some guy wants to talk to you the whole flight.
“Hey there, how’s it going?”
“I don’t know.”
“Ha ha! That’s a good one!”
“My name is Ralph, I’m in sales.”
“So what is your name?”
“I don’t know”
“You don’t know? Isn’t that a little strange?”
And depending how long they keep talking to you, gives you an idea how clueless they are to the fact that you don’t want to talk to them. Somebody who had a CF under a minute is very on the ball. Somebody who is still talking after 20 minutes is just going to be pretty oblivious to the entire world.