What's this about?
World models today predict the physical: what's where, what happens next. This paper (55↑, week's top) argues human behavior is driven by hidden mental state — beliefs, desires, intentions, social permissibility — and builds world models that track minds as well as objects.
What exactly is a "world model"?
A learned simulator the AI uses to predict consequences before acting. Adding mental state means predicting not just "the cup will fall" but "she'll be annoyed, because she asked twice" — prerequisite for genuinely social agents.
Why does it matter?
Theory-of-mind has been tested in toy benchmarks; wiring it into the world-model layer is the structural version of the idea, and the upvotes suggest the community sees it as a direction, not a gimmick.