The numbers
The slide that reframes everything: the forgetting curve. The idea goes back to Hermann Ebbinghaus, who mapped his own memory decay in the 1880s, but the figures in our workbook are from a 2019 Harvard Business Review piece — Steve Glaveski's "Where Companies Go Wrong with Learning and Development" (HBR.org, October 2019). Immediately after learning: 100% retention. Twenty minutes later: 58%. One hour: 44%. Nine hours: 36%. One day: 34%. Two days: 28%. Six days: 25%. Thirty-one days: 21%. Read that again — within one hour, more than half is gone. Within a day, two-thirds. A month later, a fifth remains.
Repeat, exercise
The steepest losses happen absurdly early, which means the countermeasure has to start absurdly early too. My two-word note on this page is the entire prescription: repeat, exercise. Retention is not a property of how well the content was presented; it is a property of how often and how actively it was retrieved afterwards. Every retrieval — a recap quiz the same afternoon, a drill the next morning, a real application in week one — flattens the curve. Passive re-reading barely helps; active retrieval is what does the work. Writing this journal tonight is itself the countermeasure. I am at hour nine; these posts are my 36%-checkpoint retrieval.
The trainer's counter-attack
I turned this topic into a one-page trainer's guide (poster below), and building it forced me to organise the countermeasures into a system. Two weapons against forgetting. Spaced learning: don't teach once and end — revisit important ideas at increasing intervals; the longer knowledge must survive, the more deliberately you plan to revisit it. Retrieval practice: don't only remind them — ask questions that require recall without looking, because retrieval strengthens memory far more than re-reading or review. The trainer's formula chains them into a cycle: teach → retrieve → apply → feedback → space → repeat. Every return to the material, with successful retrieval and application, makes the memory stronger. Two techniques I want to make habits. The 3-2-1 retrieval at the end of a session: write three things you learned, two things you will apply, one action you will take immediately — and at the start of the next session, reconstruct the answers before looking at your notes. And a 30-day reinforcement blueprint: a 3-minute quiz within 24 hours, an application scenario at day 3–7, peer discussion or coaching in week 2 ("where did you apply it, what happened?"), and a new problem in week 4 without naming which framework to use. And one don't: never ask only "do you understand?" — understanding while looking is not the same as being able to retrieve and apply later. Ask for a paraphrase, an example, a what-would-you-do instead.
Case Study
placing SOP checkpoints against the cliff
Where the curve bites us hardest: new-hire SOP training. The traditional plan — a three-day classroom marathon covering everything from fire safety to folio adjustments, then straight onto shift. By day 31 they retain around a fifth of it, and not necessarily the fifth that prevents accidents. The redesign is not more training — it is scheduled retrieval, with checkpoints deliberately placed against the curve's cliff. Each critical SOP gets retrieved on day 1, day 2, day 6 and day 30 — the exact points where the workbook's data shows retention collapsing to 34%, 28%, 25% and 21%. The retrieval is active and cheap: a five-question standup quiz, spoken rather than written, because listening is one way to measure; or a two-minute demonstration of the task under observation. The insight that changes the economics: the fix costs almost nothing. Four short retrievals per SOP, minutes each, scheduled into shifts that already exist — versus re-running the three-day marathon when audit findings reveal nobody remembers the deposit policy. The forgetting curve is not a tragedy, it is a schedule. Design against it.
Reflections
One habit for myself, starting tonight: this journal gets its own day-2, day-6 and day-31 re-reads. The curve applies to me too, and I would rather be the boy who hears whistling.