‘I’ve come to the conclusion Sweller’s Cognitive Load Theory is the single most important thing for teachers to know’ – Dylan Wiliam, 2017
What is Cognitive Load Theory?
Cognitive Load Theory (CLT) is based on two assumptions about the human brain: first, that the cognition process has two parts, working memory and long-term memory; and second, that ‘schemas’ (sometimes called ‘schemata’) are cognitive structures that allow information temporarily stored in working memory to be transferred into long-term memory and thus reduce working memory load.
CLT also says that our working memory – the place in our brain where we think about things – can only deal with a very limited amount of information at one time. Here is Frederick Reif’s 2010 description of cognitive load: ‘The cognitive load involved in a task is the cognitive effort (or amount of information processing) required by a person to perform this task’.
John Sweller is regarded as the doyen of Cognitive Load Theory and his work on it since the 1980s has been very influential. Sweller’s work built on the research of others, notably George Millar, whose research in the 1950s suggested that the maximum number of items that can be held in memory for a short period of time is about seven, and Peterson and Peterson who demonstrated in 1959 that information stored in working memory will be lost within about 30 seconds if it is not ‘rehearsed’. In 2006, together with Paul Kirschner and Richard E. Clark, Sweller published a very influential paper, ‘Why minimal guidance during instruction does not work: an analysis of the failure of Constructivist, Discovery, Problem-based, Experiential, and Inquiry-Based teaching’, which drew extensively on Cognitive Load Theory and made a compelling case for explicit instruction as the best way to teach; their key point being that only by breaking learning up into small chunks, explaining very clearly, modelling, providing worked examples and so on, can teachers ensure that students’ capacity to learn is not overloaded.
Why does Cognitive Load Theory (CLT) matter?
CLT explains that it is easy for us as teachers to unwittingly overload our students’ capacity to learn. For a significant period of time, many teachers were using techniques influenced by theories of how we learn ‘naturally’ in the real world. Discovery learning and problem-based learning are two examples of real-world learning techniques that have enjoyed significant take-up in schools at various times over the years – CLT counsels strongly against using real-world learning techniques such as these in classrooms for the teaching of new knowledge.
Comparing the real world with classrooms, CLT references the work of David Geary (Geary, 1995), who has explained that humans are programmed to learn some things automatically and unconsciously – he called this ‘instinctive knowledge’ – such as our ability to recognise faces, problem-solve, conduct social interactions and, crucially, listen and speak our native tongue – we do not need to go to school to learn this ‘Biologically Primary Knowledge’. On the other hand, there are many things that we are not programmed to learn instinctively, including how to read and write, and the content of all of the discrete school subjects – science, English, maths, history, geography, music, foreign languages and so on. For this ‘Biologically Secondary Knowledge’ we need to be taught it.
Whilst working memory can be seen as short term and finite, long-term memory can be seen as infinite. A key aim of teaching should therefore be to move knowledge to long-term memory, because when a student is exposed to new material, they can draw on this prior knowledge in their long-term memory to significantly reduce cognitive load.
To reduce cognitive load, we should:
1. Be explicit: tell students what they need to know; use models, worked examples and other forms of scaffolding that can fade, slowly, as expertise builds; check for understanding; provide feedback; provide frequent opportunities for retrieval practice etc …
2. Avoid using problem-solving activities unless and until students have a sufficient grasp of the knowledge to not be overloaded by learning in this way: ‘Futile searches for problem solutions during problem-based learning impose a heavy working memory load with no discernible advantage’ (Sweller, 2017).
3. Avoid adding additional unnecessary visual or auditory information beyond that which is needed to explain a thing – keep it simple and concise and unfussy. Greg Ashman makes this particular point thus, in his June 2018 ResearchEd article, ‘Battling the bandwidth of your brain’: ‘Remove those fancy borders, animations and cartoons unless they are fundamental to what is being communicated’.
4. Present information through both the visual and the auditory mode to increase working memory, provided both sources of information are essential and not redundant; this is about the effective use of dual coding, as opposed to assuming that including dozens of images will automatically enhance learning – they won’t, and indeed they may well harm it.
5. Use written information to support understanding. Written information has a permanence that spoken information does not have; students can return to it again and again.
The take-aways
1. When teaching novel information, we need to be aware of the severe limitations of working memory.
2. Cognitive Load Theory suggests strongly that explicit teaching works best, especially the use of examples (worked examples, partially-worked examples, What a Good One Looks Like etc), because these reduce the load and significantly aid learning.
3. Activities such as discovery learning and problem-solving are likely to overload students’ working memory, with the result that learners can engage in these activities for extended periods and learn almost nothing.
4. Frequent retrieval practice increases the chance of knowledge being stored in long-term memory – which is exactly where we want it.
Maybe Cognitive Load Theory is not quite the single most important thing for teachers to know, but it’s up there.
