A 5-Minute Guide to: Cognitive Load Theory

Thinking takes place in working memory. However, our working memory is limited both in terms of the space it has to think and how long it can hold information. These limits are the bottleneck of learning.1

Cognitive Load Theory explores the limits of working memory and how these can be overcome. Dylan Wiliam has described this as ‘the single most important thing for teachers to know’.2  If teachers need to know it, then school leaders need to know it too. 

What is cognitive load? 

Anything that takes up space in our working memory can be thought of as causing cognitive load. The right amount of the right type of load is likely to lead to learning. The wrong amount of the wrong type will hold learning back. The reason is because our working memory can only cope with a limited amount of load at one time. Once its limit is exceeded, working memory goes into cognitive overload, whereby thinking slows down, we stop understanding things, and we make mistakes. If we want students to learn, then we need to ensure there is load, but not too much load, and not the wrong type.3

Types of load 

There are two types of cognitive load: 

  1. Intrinsic load 
  2. Extraneous load 

Effectively, intrinsic load is ‘good load’ and extraneous load is ‘bad load’. That’s perhaps oversimplifying things a little, but it helps to reinforce a key point: to maximise student learning, we should be aiming to optimise intrinsic load and minimise extraneous load.4

Optimising intrinsic load

Intrinsic load is the natural, unavoidable load caused by thinking about anything. It is essential to learning. 

Although I have suggested that it is ‘good load’, as is often the case, we can have too much of a good thing. Too much intrinsic load will lead to cognitive overload. Hence, we are trying to optimise it. 


A useful analogy is weightlifting. If we are to build muscle, we need weights to feel heavy, but not too heavy. The same is true of intrinsic load. We need intrinsic load if we are to learn. If there isn’t enough, we are likely to get bored. If there is too much, we get cognitive overload. As we have said, optimising intrinsic load is our goal. 

If we expect our working memory to think about too much at one time, or about content that is too complicated, we will overload it. As a result, we will stop being able to think, we will make mistakes, and learning will stop. 

Complexity of content 

The amount of intrinsic load that working memory experiences is related to the complexity of content being presented. The more complex content is, the more intrinsic load it is likely to cause. For example, the calculation 346 × 654 is likely to cause more intrinsic load than 6 × 12. 

The word ‘likely’ is important. The amount of intrinsic load caused by particular content will vary from student to student, depending on what they know or can do already. In other words, the amount of intrinsic load students experience will depend on the knowledge they have stored in long-term memory. Those with larger, better organised stores – relevant to the content being thought about – are likely to experience less intrinsic load than those with the opposite.5

Accordingly, ensuring students have secure prerequisite knowledge before teaching new content is essential for teachers if cognitive overload is to be avoided. This can be built on, gradually. As students learn more, they will be able to cope with more. 

The importance of background knowledge

Intrinsic load helps explain why teaching students a broad, deep body of knowledge is so important. If students don’t have prerequisite knowledge stored in long-term memory, they will have to look this up and hold it in working memory. As well as making the learning process laborious and slow, this causes avoidable intrinsic load. This load could be avoided if the knowledge students needed was stored in their long-term memory. Here, it could be accessed quickly, as and when required. The space now available in working memory could be used for thinking, rather than for temporary storage. 

Just as building muscle allows us to lift heavier weights, developing long- term memory allows students to think about more complex things. 

Break it down

Excessive intrinsic load can also be avoided if complex content is broken down and presented in smaller, cumulative chunks. The natural intrinsic load of the content is still there, but this is processed gradually, rather than all at once. Long-term memory can be used to store each chunk, giving working memory access to it, when required. Once learned, one by one the chunks can be brought together and processed in working memory. Now students are able to think about the full complexity of the content, but the load is reduced. Long-term memory is helping working memory out. 

Minimising extraneous load 

Extraneous load is the unnecessary, avoidable load associated with how content is presented. Because it doesn’t lead to learning, it can be thought of as ‘bad load’. We aren’t trying to ‘optimise’ extraneous load; we are trying to minimise it. 

Extraneous load tends to be caused when students are expected to pay attention to too much at once. Quite simply, there is too much information coming at them. For example: 

  • Our slides are crammed with text, much of which is unnecessary. 
  • Our slides are crammed with clipart.
  • Our explanations are too wordy and long-winded.
  • There is too much noise in the room.
  • Students have to look at multiple sources of information at one time in order to understand what is being presented. 

Because all of these things cause extraneous load, none of them are good for learning. The more extraneous load there is, the less intrinsic load working memory can process. Hence, the less it can think about the things that are most important for it to be thinking about. 

Careful instructional design is the key to minimising extraneous load and freeing up as much working memory as possible for thinking. 

Taken from The Teaching Delusion 3: Power Up Your Pedagogy by Bruce Robertson, published by John Catt Educational. 

Available at:


  1. Lovell, O. (2020) Sweller’s Cognitive Load Theory in Action. Woodbridge: John Catt Educational Ltd.
  2. https://impact.chartered.college/article/shibli-cognitive-load-theory-classroom/
  3. Barton, C. (2018) How I Wish I’d Taught Maths: Lessons Learned from Research, Conversations with Experts, and 12 Years of Mistakes. Woodbridge: John Catt Ed
  4. Lovell, O. (2020) Sweller’s Cognitive Load Theory in Action. Woodbridge: John Catt Educational Ltd.
  5. Lovell, O. (2020) Sweller’s Cognitive Load Theory in Action. Woodbridge: John Catt Educational Ltd.
  6. Barton, C. (2018) How I Wish I’d Taught Maths: Lessons Learned from Research, Conversations with Experts, and 12 Years of Mistakes. Woodbridge: John Catt Educational Ltd.

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