This is a Lexicon entry: the mechanism, when it shows up, and the countermeasure. The full correction, with real-world cases and the audit prompt, hasn't been written yet.
Definition
If you cannot explain something clearly to a child, you do not fully understand it yourself. The inability to simplify is a reliable indicator of incomplete understanding - often masked by technical vocabulary, authority and complexity. Genuine mastery produces simple explanations; apparent mastery produces complicated ones.
When it shows up
When explaining something you have studied; when an expert communicates with a non-expert audience; when you feel confident about a topic but struggle to explain it simply. In any expert field: when understanding your own calibration helps you communicate uncertainty to stakeholders. In research: when hypothesis pre-registration forces you to articulate your prior before seeing data.
Failure mode
Mistaking jargon fluency for genuine understanding. Explaining complexity with more complexity. Using technical language that conceals rather than reveals the underlying mechanism.
Countermeasure
Apply the Feynman Technique: attempt to explain the concept in simple language as if to a beginner. Where your explanation breaks down is where your understanding is shallow. Return to source material and resolve the gap.
Related traps
Also connected in the mapThe Curse of Knowledge·3 more, locked
Credit & first seen
DiscoveredFeynman, R.P. (1974).Cargo Cult Science.Caltech Commencement Address. Reprinted in Surely You're Joking, Mr. Feynman! (1985). W.W. Norton source ↗
Read next
Entry #542 of 631 in The Lexicon · see the full Lexicon