The Feynman Technique: Prove You Understand It
Why rereading feels like learning
In 2013, Dunlosky and colleagues reviewed 10 common study techniques and rated rereading and highlighting as low utility, while practice testing and distributed practice earned the highest ratings. Rereading feels productive because the page looks familiar, but familiarity is recognition, not recall. The Feynman technique is a cheap way to test which one you actually have.
The four steps
- Pick one concept and write its name at the top of a blank page.
- Explain it in plain words, as if teaching a smart 12-year-old, with no jargon and one concrete example.
- Mark every spot where your explanation turns vague or circular. Those spots are your real gaps.
- Go back to the source only for those spots, then rewrite the explanation from scratch.
Worked example: compound interest
Weak version: interest is calculated on the principal plus accumulated interest. Teach-back version: put 100 dollars in an account paying 10 percent a year. After year one you have 110 dollars. In year two the 10 percent also applies to the extra 10 dollars, so you earn 11 dollars, not 10. That extra dollar is the whole idea: growth itself starts growing. If you cannot produce the numbers without looking, you do not own the concept yet.
Where people cheat
The common failure is writing a summary while looking at the source. That tests copying, not understanding, so close the book before you write. A second failure is explaining at full length: a teach-back that needs pages of setup usually hides a vague core. Aim for an explanation a listener could repeat back in one minute.
Summary
Understanding is what survives a blank page. Explain it simply, find where the explanation breaks, repair only that spot, and repeat until a listener could teach it onward.