Externalize your mental models

The idea

A mental model you cannot draw is a mental model you cannot examine. The models that govern your decisions most powerfully are the ones you have never made visible — and therefore never inspected, never tested, and never improved.

In 1943, the Scottish psychologist Kenneth Craik published a slim, extraordinary book called The Nature of Explanation. Craik proposed that the human mind works by constructing "small-scale models" of reality — internal representations that mirror the structure of external events and allow us to anticipate what will happen next. Thinking, Craik argued, is not the abstract manipulation of symbols. It is the running of simulations on internal models that parallel the world (Craik, 1943).

An example

A product manager believes her team ships slowly because engineering is understaffed. She has held this belief for eighteen months. It drives her hiring requests, her sprint planning, her escalations to leadership. When asked to draw her mental model of the shipping pipeline on a whiteboard, she maps: requirements flow to engineering, engineering builds, QA tests, product ships. The drawing takes ninety seconds. Then she stares at it. There is no feedback loop from QA back to requirements. There is no node for cross-team dependency resolution, which consumes roughly 30% of every sprint. There is no representation of the approval bottleneck where three stakeholders must sign off sequentially. The drawing reveals that her model is missing the three largest sources of delay — none of which are solved by hiring. She has been optimizing for a problem that exists in her mental model but not in reality. The real system, once drawn, suggests entirely different interventions.

Where it goes wrong

Describing your mental model in prose instead of drawing it. Writing a paragraph about what you believe preserves the linear, narrative structure that hides gaps. A paragraph can skip over missing relationships because language flows forward and the reader — including you — fills in the blanks automatically. A diagram cannot skip. Every box must connect to something. Every arrow must point somewhere. The spatial layout forces you to confront what is missing, what is disconnected, and what is circular. If you externalize your mental model in words alone, you will produce a convincing story, not an inspectable structure. Stories persuade. Diagrams reveal.

Make it stick

You have now practiced making your mental models visible — turning implicit structures into explicit diagrams you can inspect, challenge, and revise. But mental models are not the only invisible cognitive structure that governs your behavior. When you encounter a problem, you do not simply apply a model — you chain together a sequence of reasoning steps, each dependent on the one before it. These reasoning chains are just as invisible as your models, and just as vulnerable to hidden errors.