A common area of overconfidence: judgements about what other people are thinking or valuing.
I often notice people concluding that someone they have some reasons to admire is either making a naive mistake, or else does not in fact share their values.
Often, the truth is that person 1 is weighing considerations that person 2 does not recognise, or pursuing a strategy person 2 has not thought of. And person 2 is not sufficiently adjusting for this possibility.
The mistake is especially common when two people are separated by greater inferential distance than they realise.
It’s natural to assume that, if someone shares your values and is acting reasonably, it would be fairly easy to understand them. But there are strong reasons to doubt this. Everyone knows lots of things that you do not, everyone’s brain is trained differently. Another person’s reasoning may not be legible to you after a cursory or even a fairly close inspection—or even after you’ve asked them to state their reasons, and they have tried. Yet it may still be good.
Careless strawmanning can lead us to badly underrate people who—by our own lights—we ought to admire, or at least take seriously. I know many people who severely underestimate figures like Tyler Cowen and Peter Thiel, partly due to this effect.
Things get especially bad for people who tend to overindulge in general cynicism about motives.
The principle of charity is a strong antidote. So is the general attitude of “Most of my judgements are mostly wrong—I must keep attending, I must keep listening”.