Kahneman: Expert behavior is in System 1. Most of the time we are expert in most of what we do. Sometimes it's very striking. I like the example that I pick up the phone, and my wife, Anne, says one word and I know her mood. That's very little information, but it's enough. That is expertise of a high order. How did it come about? It came about through reinforced practice, a lot of reinforcement, and a lot of practice. All of us are experts on things. The stories about fireground commanders, or about physicians who have those marvelous intuitions, they're not surprising if they have had the opportunity to learn as much about their field as I have learned about Anne on the telephone, then they're skilled. It's in System 1; it comes with complete confidence.
What's interesting is that people also have intuitions that they're equally confident about except they're wrong. That happens through the mechanism that I call "The mechanism of substitution." You've been asked a question, and instead you answer another question, but that answer comes by itself with complete confidence, and you're not aware that you're doing something that you're not an expert on because you have one answer. Subjectively, whether it's right or wrong, it feels exactly the same.