This is a very good thread with a lot of excellent points, and more show up in the comments. I'd like to revive it.

One obvious explanation for teenagers having malleable minds that, to me, is strikingly missing, is status. Teenagers have low status, pretty much the lowest in society. People tell them they're annoying all the time, and they're alotoftimes depressed, which causes them to perceive themselves as low-status.

It's the inverse of this great speculative article. If high status makes you unable to change your mind, then maybe low status makes it easy to change your mind. Maybe if you have low status, the strategy to get high status is to prove that a formerly high-status belief is wrong. If beliefs are as attached to status as people like Planck suggest, this makes actual truth-seeking a viable strategy in low-status hunter gatherers.

Metadata: I am 19 and perceive myself as low-status. I also find that I change my mind very easily most of the time, but that could just be self-serving bias causing me to think that.