“There’s a baked-in assumption in RPGs that humans are rational actors that I think is interestingly political and mostly unexamined.” – Paul Beakley  – SO very much this. I spent mumblety-mumble years in academia going down the psychology rabbit hole and our ability to manage our own behaviour is sooo much smaller than we appreciate. (Even me, after all this time.)
I mean, gamers can argue for a million years about realism in combat mechanics and gun statistics but the fact that players have perfect control over their character’s behaviour is eternally ignored and renders that whole argument ludicrous.
I love games that complicate that stuff somehow. Wraith’s Shadowguide comes to mind – another player whispering stuff in your ear is a pretty blunt way to model non-linear internal processing, but it certainly has a visceral punch to it.
So that’s my answer – human psychological reality. I look forward to better systemic support for this (in games that it suits).