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Why Ebbinghaus' forgetting curve isn't useful for teaching

Ebbinghau's forgetting curve has seen a resurgence in popularity, especially as teachers push back against the curriculum model based principally on skills and not domain specific knowledge and thinking.


While I agree that knowledge is essential for domain specific understanding and thinking, I argue here that Ebbinghaus' experiment, which has been generalised by many as a model of learning and forgetting is not a useful model for teaching. It is not an argument against retrieval practice.





What the Ebbinghaus curve shows


Ebbinghaus conducted an experiment on himself (n=1) to see how long he could retain nonsense words. The curve thus shows how long it took one person to forget completely and utterly isolated facts.


What the Ebbinghaus curve does not show


The curve doesn't allows us to know anything about forgetting of anything but isolated facts.


The distinction between facts and isolated facts is important. I cannot imagine any teachers ever teaching isolated facts. The discussion I see on Twitter seems to often be about contextualisation and the sequencing of content for optimal understanding. Not only do teachers go to great efforts to ensure new content is never isolated, students also bring a wealth of prior knowledge from other subjects and their lives to connect to and find meaning.


While we must always search for simplified (idealised) models to help our thinking, useful models are those that help us approximate reality. If we, as teachers, are working towards connected, networked, meaningful knowledge then we must question the popularity of a model that does not allow us to think precisely about these things. This is especially made worse when the graphs of precise timings and percentage of forgetting are shared with students.


Furthermore, while the Ebbinghaus curve remains popular as a go-to mental model of forgetting for both teachers (and for students when shared with them), it diverts attention away the more complex reality of learning. That complex reality of learning is actually our goal. Ebbinghaus' forgetting curve may be intuitive and easy, but it takes us away from where we want to go and the type of learner we want to build.


The Ebbinghaus forgetting model has become a sort of zombie model that is permeating the teaching community with a lack of questioning of its utility. It's a zombie because as a profession we don't work this way with students, yet it remains.


If we need to instill an idea of learning and forgetting, can't we just talk to our students about how humans forget and we must revisit concepts? I don't think we need to refer to Ebbinghaus in an effort to obtain authority over the idea. I think humans find the idea of forgetting quite intuitive (it happens all the time). How about a model that focuses on forgetting in more useful fashion?


An idealised and useful model of learning and forgetting: Ausubel


Ausubel's theory of learning, at its simplest, makes a stark distinction between rote learning and meaningful learning. Rote learning is the learning of isolated facts, that is they don't hold connections to other knowledge. Meaningful knowledge is the opposite, new knowledge being incorporated into a growing cognitive network (Figure 1).


Figure 1. Copied from: Novak, 2010. Learning, Creating, and Using Knowledge

With forgetting, Ausubel made the useful distinction again between rote and meaningful, which I think is much more useful than the quantified Ebbinghaus curve. Rote learning, once forgotten is lost forever, but with forgetting meaningful learning the cognitive structure, the network configuration we could say, (or maybe even the new general way of seeing that knowledge) remains.


The details go, but some understanding persists. When we want to revisit the learning, the details are incorporated rapidly into the structure that remained. With revisiting rote learning, the learning is from scratch.


While this is also an idealised model, it diverts our attention to meaningful learning as the goal of knowledge, rather than just the retention of (any) knowledge. This in itself is much more useful as the models we hold closest affect how we and our students perceive the course and its objectives.


A teacher could sketch an Ebbinghaus forgetting curve on the board to make a point, but to stop there is to limit student and teacher thinking about learning. In my opinion it would be more useful to draw an idealised (without words) concept map on the board, emphasising the connections, and then rub out some nodes to show forgetting while the structure remains (Figure 2).


Figure 2: A simple attempt at showing Ausubel's model of forgetting meaningful learning


This expresses more clearly that connected knowledge in meaningful mental models is the goal of learning, and thus, when students engage in retrieval practice they should have in mind that those closed questions in isolation should be building to something more bigger and connected. (See my post here on core question design).


Ebbinghaus: Focus on forgetting isolated knowledge. Quantified timings and percentages.


Ausubel: Focus on learning and forgetting connected, meaningful knowledge. Qualitative.


For biology teachers: if you are insterested in networked knowledge in our subject, I have a paper published on it here. DM if you want to read it.


Christian Moore Anderson

@CMooreAnderson (follow me on twitter)


Find my other posts here


References


Novak, J. D. 2010. Learning, Creating, and Using Knowledge: Concept Maps as Facilitative Tools in Schools and Corporations. 2nd ed. Oxford: Routledge.


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