In 1885, a German psychologist named Hermann Ebbinghaus ran an experiment on himself. He memorised lists of nonsense syllables and recorded how quickly he forgot them. What he found — replicated across hundreds of subsequent studies — is that unreinforced information decays steeply in the hours after exposure. Most of it is gone within a day.
Ebbinghaus was testing meaningless syllables in a laboratory. AEC professionals are learning building physics, fire safety specifications, and structural design principles in a hotel meeting room. The conditions are not identical. But the directional finding is the same, and the professional development sector has spent 140 years largely ignoring it.
Here is the question worth sitting with: of the CPD sessions you attended last year, how much do you actually remember? Not remember attending. Not remember enjoying. Remember — in the sense of being able to recall the specific argument, the cited evidence, the changed assumption, the decision you made differently three months later.
For most professionals, the honest answer is: very little. This is not a failure of attention or intelligence. It is a predictable consequence of the format in which almost all CPD is delivered.
Why passive attendance is the wrong format for retention
In 2009, Karpicke, Butler and Roediger surveyed 177 undergraduate students on how they studied. Eighty-four percent listed rereading as their primary strategy. Only one percent mentioned self-testing.
This matters because rereading produces something that feels indistinguishable from learning but isn’t. Each pass through familiar material creates fluency — the content seems easier, more recognisable, more graspable. Learners interpret this as understanding. Cognitive scientists call it the fluency illusion. The material has not been encoded into long-term memory. It has been temporarily activated, and that activation feels like retention.
Robert Bjork formalised the underlying principle in 1994 as “desirable difficulties” — the observation that conditions which slow apparent learning during practice accelerate actual long-term retention. Rereading is easy and feels productive. Retrieval is effortful and feels slow. This is precisely the relationship Bjork documented: the technique that feels harder works better.
A CPD session delivered as a presentation — slides, speaker, questions at the end — is the professional equivalent of rereading. The professional is exposed to content. They recognise it, engage with it, may even discuss it. Then they leave, return to a live project, and the content decays at exactly the rate Ebbinghaus described, because nothing has interrupted that decay.
The session was not poor. The speaker was not unprepared. The format was wrong — not wrong for engagement, but wrong for retention. And retention is the only measure that connects a CPD session to a professional outcome.
What the evidence says actually works
Three findings from the retention literature have direct application to professional CPD. They are not complicated interventions. They are attention, recall, and timing — structured deliberately.
Retrieval practice. Roediger and Karpicke (2006) demonstrated that students who retrieved information through practice tests retained substantially more after a week than students who restudied the same material four times. A subsequent meta-analysis by Adesope, Trevisan and Sundararajan (2017), covering 118 studies, confirmed effect sizes of g=0.51 compared with restudy and g=0.93 compared with no activity. The mechanism is well understood: the act of retrieval does not merely test whether learning occurred — it strengthens the memory trace. Every time you successfully retrieve a piece of information, the neural pathway encoding it is reinforced. The test is the training.
The implication for CPD is specific. Asking “what do I intend to do differently as a result of this session?” immediately after attending is a retrieval event. The professional must actively recall the session, identify its most relevant content, and articulate a specific application. That act of recall produces better retention of the session than taking a second look at the slides.
Spaced review. Cepeda and colleagues’ (2006) meta-analysis of 839 assessments across 184 studies established that distributed practice — returning to material at intervals rather than in a single massed session — produces substantially better long-term retention than equivalent time spent in continuous review. The optimal gap between initial exposure and review falls broadly in the region of 10–30% of the intended retention interval: for material you want to retain for a month, a review somewhere in the first week is meaningfully better than a review at day one or day twenty-eight. Their 2008 follow-up refined this further: for longer retention targets, the optimal gap shifts proportionally. The practical translation is that a 30-day check-in — timed to fall within that window — is not arbitrary. It is the interval the literature identifies as most effective for converting initial exposure into durable knowledge.
The pretesting effect. Pan and Carpenter (2023), synthesising sixty-plus peer-reviewed studies, found that attempting to answer a question before a learning event improves subsequent retention compared with equivalent study time alone — even when the initial attempt is wrong. The proposed mechanism is that an incorrect attempt creates a cognitive gap that the subsequent learning fills more completely than it would have otherwise. Approaching a CPD session having first articulated “what do I expect to understand better after this?” is not a bureaucratic pre-task. It is an attentional primer. The professional who does it will retain more from the same session than a colleague who arrived without it.
These three findings converge on the same structural point: the session itself is not the learning. The learning happens in what surrounds the session — the anticipation before it, the retrieval immediately after it, and the spaced review in the weeks that follow.
What this means for how CPD works
The session format cannot change overnight. Providers who have been delivering structured presentations to AEC professionals for ten years are not going to restructure their programmes into retrieval-practice workshops before next month’s booking. The content is often good. The evidence base is often solid. The format is the problem, and the format is constrained by the conventions and expectations of the market.
What can change is the frame around the session.
The pre-attendance question — “what do I expect to get from this?” — is a pretesting mechanism. It costs thirty seconds and primes the entire session.
The post-attendance submission — “what do I intend to do differently?” — is a retrieval event. It forces active recall and specific articulation at exactly the moment when the memory trace is freshest and most amenable to consolidation.
The 30-day check-in — “did you act on what you intended?” — is a spaced review. Timed to fall within the window the literature identifies as optimal, it serves two purposes simultaneously: it assesses whether the intent was enacted, and it reactivates the learning at the interval most likely to extend its retention.
CPD Impact did not design these features from the retention literature and then construct a platform around them. It designed them because they are honest instruments for measuring whether CPD produces professional change. The alignment with cognitive science is a consequence of that honesty — the mechanics that genuinely capture professional development turn out to be the mechanics that cognitive science already knew produce it.
The gap the sector has always known about
There is a strand of professional education research that has documented the gap between CPD delivery and retention for decades. Guskey (2002) noted that most professional development evaluation stops at participant satisfaction — the lowest, least informative level — and rarely reaches evidence of changed practice. In healthcare, aviation, and law, where the consequences of retained incompetence are visible and acute, the sector has developed more rigorous evaluation infrastructure. In AEC, the evaluation infrastructure has not existed.
This is not an argument that AEC professionals are indifferent to learning. Most are not. It is an argument that the system around the learning — what happens before, during, and after the session, what is recorded, what is followed up, what is evaluated — has been designed for compliance rather than retention.
The techniques that produce durable professional learning are not exotic. They are well-documented, relatively simple, and almost entirely absent from the standard CPD experience in AEC. The question is not whether the profession knows they exist. It is whether there is any infrastructure to make them routine.
FAQs
Q1: Why do I forget most of what I learn in CPD sessions? A1: The dominant CPD delivery format — lecture or presentation — produces what cognitive scientists call the fluency illusion: material feels familiar during exposure, which learners mistake for learning. Research on memory decay (Ebbinghaus, 1885, widely replicated) demonstrates that unreinforced information decays steeply in the hours after exposure. The techniques that produce durable retention — retrieval practice, spaced review, elaborative questioning — are almost entirely absent from standard CPD delivery. You are not forgetting because you weren’t paying attention. You are forgetting because the format was not designed to produce retention.
Q2: What does research say is the most effective way to retain learning from a CPD session? A2: The two techniques with the strongest evidence base are retrieval practice — actively recalling information rather than re-reading it — and spaced review, returning to material at structured intervals. Meta-analyses across 118 studies (Adesope et al., 2017) show effect sizes of g=0.51 for retrieval practice over restudy and g=0.93 over no activity. Research on distributed practice (Cepeda et al., 2006, 839 assessments across 184 studies) confirms that reviewing material within broadly 10–30% of your intended retention interval substantially outperforms massed repetition. Asking “what do I intend to do differently?” immediately after a CPD session is a retrieval event. Checking 30 days later whether you followed through is a spaced review. Both are more effective for retention than taking notes during the session.
Q3: How does the CPD Sniff Test help with retention? A3: The Sniff Test pre-commitment question — “what do I expect to get from this session?” — activates the pretesting effect: research synthesising over 60 peer-reviewed studies (Pan & Carpenter, 2023) shows that attempting to answer a question before a learning event improves subsequent retention compared with equivalent study time alone, even when the initial answer is wrong. By articulating an expectation before attending, you prime your attention toward information relevant to that question during the session. You will retain more from it than a colleague who attended without that pre-commitment — not because anything about the session was different, but because of what you did before you arrived.
