In 1885, Hermann Ebbinghaus ran a memory experiment on himself, learning strings of nonsense syllables and testing how much he could recall over time. The finding attached to his name is now one of the most cited results in the psychology of learning: without reinforcement, most new information decays fast. The specific figure often quoted — 70% forgotten within 24 hours — comes from a single study using artificial material under laboratory conditions, and shouldn’t be treated as a precise statistic for professional learning. But the direction of the finding has held up for well over a century: unreinforced learning decays quickly, and it decays predictably. CPD, as currently structured across the AEC sector, is built as though this were not true.
It isn’t a personal failing — it’s a design failure.
It’s tempting to read the forgetting curve as evidence that attendees don’t try hard enough to retain what they’ve heard. Donald Norman’s argument in The Design of Everyday Things points the other way: when a system produces the same foreseeable outcome again and again, the fault usually sits with the system, not the person using it. Apply that to a typical CPD session. There’s nowhere to record what you intended to change afterwards. No prompt to retrieve it later. No mechanism that asks, a month on, whether it was used. Nothing about the format asks the brain to do the one thing that produces durable memory — retrieving it, under some effort, after time has passed. The forgetting curve isn’t proof that AEC professionals have poor memories. It’s proof that CPD, as an environment, was built — by accident, through decades of habit — to maximise forgetting. That reframing matters, because it changes the question from “how do we get people to try harder” to “what would a session need to include for retention to be the expected outcome, not the exception.”
The measurement problem makes it worse.
There’s a second, less comfortable implication, and it comes from an unlikely source: Nassim Taleb’s concept of antifragility, which rests on the observation that systems optimised for comfort and systems optimised for durability are not the same systems — removing all friction from something often makes it weaker, not stronger. CPD that is polished, frictionless, and easy to sit through is comfortable. That doesn’t make it more likely to change anything. A session that challenges an assumption an attendee had stopped questioning — that makes them reconsider a specification decision — is, almost by definition, less comfortable to sit through than one that simply confirms what they already believed. A satisfaction survey handed out five minutes after the session ends will reward the comfortable session and mark down the challenging one, every time. That isn’t a minor measurement quirk. It means the most common CPD evaluation instrument in the sector is quietly selecting against the sessions most likely to produce real competence change, while reinforcing the ones least likely to.
Retrieval, not repetition, is what closes the gap.
Cognitive science has a specific, well-replicated answer to the forgetting curve, and it isn’t “try to remember harder.” It’s retrieval practice: actively recalling information at a later point, under some effort, consolidates it far more effectively than passive re-exposure to the same material. Roediger and Karpicke’s 2006 study remains the clearest demonstration of this — testing memory, even briefly, produces markedly better long-term retention than simply restudying the same content for the same amount of time. Spacing compounds the effect. Cepeda and colleagues’ meta-analysis of over 800 memory studies found that reviewing material at an interval broadly proportional to how long you need to remember it produces stronger retention than reviewing it too soon, too late, or not at all. Put those two findings together and a specific design implication follows: a CPD session followed by a prompt roughly a month later isn’t an administrative nicety. It’s a two-point retrieval practice sequence, spaced at an interval the research suggests should meaningfully improve retention over a session with no follow-up at all.
That’s the entire mechanical justification for the 30-day check-in built into the CPD Impact portal. It isn’t a compliance step bolted onto a platform. It’s the point in the design where the forgetting curve gets interrupted — the moment a learner is asked to retrieve, rather than simply recall having attended.
None of this requires new pedagogy, a change to session format, or any additional effort from CPD providers. It requires one addition: a structured moment, roughly a month later, that asks whether what was learned actually got used. That’s a designed retrieval event, not paperwork. The Realisation Rate — the percentage of sessions where a professional confirms they acted on what they intended to change — is what that retrieval event produces as data. It’s a number generated by doing the thing that makes learning stick, which happens to also be the thing that measures whether it did.
FAQs
The commonly cited figure — 70% forgotten within 24 hours — comes from Hermann Ebbinghaus’s 1885 experiments using nonsense syllables under laboratory conditions, so it shouldn’t be treated as a precise statistic for professional learning specifically. What has been repeatedly replicated since is the underlying pattern: without reinforcement, newly learned information decays quickly and predictably. Standard CPD delivery — a session with no structured follow-up — provides no reinforcement at all.
The most consistently evidenced method is retrieval practice — actively recalling information at a later point, rather than simply being re-exposed to it. Roediger and Karpicke’s 2006 study found that testing memory, even briefly, produces better long-term retention than restudying the same material for the same amount of time. Spacing that retrieval at an interval proportional to how long the information needs to be retained (Cepeda et al., 2006) compounds the effect.
The 30-day check-in is a designed retrieval event, not an administrative step. Cognitive science research on retrieval practice and spaced repetition indicates that a structured prompt to recall and report on what was learned, roughly a month after the original session, should meaningfully improve retention compared with a session that has no follow-up at all. The Realisation Rate is the data produced by that retrieval event — a by-product of the mechanism that makes the learning more likely to stick in the first place.
“The 30-day check-in is built into the CPD Impact portal — it’s the retrieval practice that turns attendance into retained professional development.”
