A mental model is a simplified understanding of how something works. Here the term refers to the assumptions that influence a decision or system map.

One resident may assume a bigger basket will solve the laundry problem; another may think it will merely hold a bigger pile. Their predictions point to different mechanisms worth checking.

An assumption can be explicit, partly recognised or overlooked. Calling it a mental model does not prove that it is wrong, deeply hidden or the sole cause of the routine.