I’ve come to the conclusion Sweller’s Cognitive Load Theory is the single most important thing for teachers to know https://t.co/MkJJLruR8g
— Dylan Wiliam (@dylanwiliam) January 26, 2017
What do teachers need to know about Cognitive Load Theory? The short answer is, not that much.
There’s an awful that’s been written and said about Cognitive Load Theory (CTL) in recent years and most of it is wholly unnecessary for teachers to know about. At it’s heart, the theory relies on a decades old model of human cognition, generally referred to as the Working Memory Model. It’s important to note that this model – like all models – is wrong. (The rule of thumb here is that if your brain was simple enough for you to understand, you’d be too simple to understand it.) The Working Memory Model is one of the foundations on which most of cognitive science rests as it makes useful, testable predictions about how we think and learn. Of course, science is always contingent; new models are regularly developed and old models tweaked. It may be that at some point in the future some discovery may overturn the last four decades of research in this area, but it’s not particularly likely. Regardless, currently it is the simplest and most useful model of human cognition we possess.
The Working Memory Model predicts that human beings struggle to pay attention to more than about 2 or 3 new ideas at once. But, once new information has been ‘processed’ it is stored in long-term memory which, to the best of our current knowledge, has a limitless storage capacity. The relationship between working memory and long-term memory is two way; not only are we constantly storing new information, we are also retrieving it, using prior knowledge to help us make sense of our environments. Anything we’ve stored in long-term memory can be transferred back to working memory to allow us think abstract thoughts and complete highly complex and specialised tasks and behaviours. The more familiar we are with information we’ve learned, the more automatically we are able to retrieve it. Our working memory seems to have no limits when handling familiar, previously learned information, allowing us to read and write books, build and drive cars, split the atom, discover penicillin, and vent invective on social media.
So, the Working Memory Model predicts that we have limited cognitive resources when dealing with information and ideas that are not well stored in long-term memory. These limited resources can be spent on trying to solve problems, or on storing solutions for solving problems in the future. CLT predicts is that you probably can’t do both at once, especially if the task is complex. It’s perfectly possible for students to solve problems and yet remember nothing about how to solve them again in the future. As an example, I give you the clock in my car.
This is both deeply counter-intuitive and difficult for teachers to spot. From a classroom perspective it can often seem that students understand something during the lesson only to have forgotten it by their next lesson. CLT suggests that whenever we perform a task we experience a cognitive load. If the task is simple and familiar, the load is light; if the task is complex and unfamiliar, the load is high. The theory predicts that if load is minimised during instruction students will retain more for longer.
Within CLT, learning is described as a change in long-term memory. Some people are critical of this, insisting that surely learning must be more complex than that. Well, of course learning is more complex than that, but so what? If we want to insist on a more complex definition then we would need to explain how piling up additional layers of complexity was helpful to teachers.
All teachers really need to know is this: students are unlikely to benefit from a problem solving approach to instruction unless the content is simple or familiar, but if problems are explained and discussed before students are given some guided practice, they are likely to learn more.
The cognitive load students experience can be reduced in two main ways:
- By offering support in the form of modelling and scaffolding. But, once students begin to rely on external help, it must be slowly withdrawn in order to promote internalising the support. Once students are familiar with the problems they are being asked to solve, providing additional help may actually increase cognitive load.
- By manipulating the complexity and the quantity of the task: start with an easy version of a problem before moving to a harder version, and limit the length of time students spend on a task – the longer they work, the greater the load they are likely to experience. If the quantity of a task is reduced, its complexity can be increased. And vice versa.
None of this is particularly surprising or controversial, but it does tend to contradict theories of learning that suggest children are more likely to learn if they discover things for themselves. There’s an awful lot of fairly unhelpful theory that’s been added to this solid and sensible base. Much of it is interesting, but little of it will make much difference to hardworking teachers who just want to make sure their students are making progress. If teachers embrace the two simple points above, children are likely to learn more. If they don’t, children – particularly the most disadvantaged – are likely to be worse off. As Thomas Sowell put it, “It is so easy to be wrong – and to persist in being wrong – when the costs of being wrong are paid by others.”
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