With these criteria, how does anyone make any statement about their own abilities? If you went to a job interview and they asked "What is your biggest strength?" would you say "Well, humans are prone to overestimate their abilities. I couldn't answer that question without doing a double blind research study"?
Think about it: The only way that you could change your view of your own abilities is by comparing your predictions about people's character to their actual behavior over time. Jessica did the same thing, but she found that her predictions were accurate.
JL has the opportunity to make judgements about people, and then spend months or more with them as a part of YCombinator. She can say "I don't think the members of this startup will work well together" or "I don't like the looks of this guy", and then see if she was right or not. She has the opportunity to do this dozens of times per year, every year. That's how she knows.
Think about it: The only way that you could change your view of your own abilities is by comparing your predictions about people's character to their actual behavior over time. Jessica did the same thing, but she found that her predictions were accurate.
JL has the opportunity to make judgements about people, and then spend months or more with them as a part of YCombinator. She can say "I don't think the members of this startup will work well together" or "I don't like the looks of this guy", and then see if she was right or not. She has the opportunity to do this dozens of times per year, every year. That's how she knows.