[ted12345]

I wonder if this has to do with your personality, how you behave under pressure, and how you react to not knowing the answer to something.

You seem more than capable enough to get a good job but in my experience, interviewers are looking to see how you react to being stumped. If it's anger/frustration/clamming up then that's a turn off for a lot of employers. They're looking for more than the right answer.

[p4wnc6]

What if he is merely introverted, and responds well to pressure when there is not an awkward, immediate social situation? There are lots of excellent programmers like this, you know, and also very few workplaces that actually benefit from lots of real-time interpersonal communication (as opposed to cargo culting that from startup bullshit).