I did something similar for a "game engine" let the NPCs remember things from other NPCs' and the PC's interaction with them. It wasn't perfect, but the player

I did something similar for a "game engine" let the NPCs remember things from other NPCs' and the PC's interaction with them. It wasn't perfect, but the player could negotiate a cheaper price on a dagger for instance if they promised to owe the NPC a larger payout next time they returned to the shop. And it worked... most of the time, the shop owner remembered the debt and inquired about it on the next interaction - but not always, which I guess is kind of "human".