Cognitive Load Theory (CLT)

Cognitive Load Theory (CLT) provides a framework for educators to optimise learning material and activities so that students aren’t overwhelmed.  It draws heavily from cognitive science to understand how the brain processes information.  An important part of this modelling is the dynamic relationship between our working memory and our long-term memory.

The working memory (also referred to as short-term memory) is continuously processing all the data that our senses are receiving.  It works on many levels and has to perform a lot of functions simultaneously.   It works dynamically with the more passive long-term memory to store and retrieve information at critical points.  The obvious analogy is to the interaction between a computer’s random access memory (RAM) and its less volatile HDD or SSD storage drives.

Working memory is essential for high cognitive functioning such as learning activities where we are holding and manipulating different thoughts and ideas and mentally constructing working models and scenarios.  It is a fast high turnover operation but it has limited  processing power and it doesn’t take much to overload the system; particularly in a dedicated learning situation, like a classroom or university lecture, where learners have to process a lot of complex information in a limited time.   

CLT provides us with modelling to help us understand and mitigate cognitive overload.  It classifies cognitive activity into three overlapping types:

Intrinsic load is the totality of what we are expected to know or understand about the particular subject area at the completion of the learning activities.  It is thought to be a constant that has been set (perhaps in the curriculum) and is normally not negotiable.

Extraneous load is any unnecessary information processing activity that is not fulfilling a useful role in helping the student understand what they need to know.   Extraneous load is wasteful of the student’s cognitive resources and can compromise the learning outcomes.    For example, if a teacher’s explanation is unnecessarily convoluted or confusing the learner has to dedicate cognitive resources to interpret what the teacher is trying to say. Extraneous load can come from a number of sources and they are accumulative and often compounding – each magnifying the effect of the other.      It is usually attributed to poor learning design and presentation. 

Germane load is any information or learning activity that is pertinent and useful for the learner to understand the content without going into cognitive overload.

The first thing that teachers and education designers need to do to optimise their material is to minimise the extraneous cognitive load (there are a number of tips listed below). Ideally, after that, the remaining germane load can cover the intrinsic load (the material that needs to be covered) but many concepts and subject areas are too big and complicated to be covered comfortably in one go.

Often this is because there are so many working parts that function interdependently.     It’s difficult to understand  “A” if we don’t understand “B” and “C” and we cannot understand “B” if we don’t understand “C” and “A”; and in any case “A” might be conditional on “D” and “E” in particular contexts but not others.   

If we consider this whole (admittedly very abstract) scenario to be the intrinsic load of our subject we can appreciate that it might be difficult to explain it explicitly in one go. We would probably tie ourselves in knots and our students would pretty quickly reach cognitive overload.   CLT uses the term schema to describe a collection of concepts or ideas that work together interdependently.  When we break the subject up into these more manageable but still largely autonomous and self-contained units it becomes easier for the student to process.

Importantly, a schema can be a component part of another schema and can themselves have their own sub-schemas within them.     We could conceptualise the whole scenario above as a super-schema where the individual letter components  (A, B, C etc) are sub-schemas that are nested within it.  A logical way for teachers to approach this level of complexity would be to explain what the super-schema is doing and why it is important.    The teacher could then explain what the different component letters are doing within this overall context.   It’s important that the student gets enough germane information about each component to form a working model or schema that can be safely stored in the long-term memory.  It doesn’t matter if it is a bit sketchy and incomplete, or even a bit wrong, so long as the mental modelling is reasonably cohesive and meaningful.  If there is an underlying logic it becomes more memorable and can be safely stored in the long-term memory to be retrieved, updated and corrected when necessary.

As the learner understands more about each component schema within the context of a larger schema they are able to see how and why they work together.  It’s very much a building process.  As the student becomes more knowledgeable and more self-sufficient, and less reliant on explicit explanations from the teacher.

How to avoid cognitive overload

Think time and timing.  Time is an important factor that is often overlooked. Students need time to fully process and digest information.  Relentlessly piling information on top of information will quickly lead to cognitive overload.  Leave short gaps so that students can gather their thoughts and consolidate them in their long-term memory.

Use the right medium.  Some concepts are easier to explain by showing or demonstrating rather than by convoluted oral explanation. Other concepts can be better understood by completing an activity or from observation especially once the student has understood some of the fundamental principles.   Not everything has to be explained explicitly; many things are better understood tacitly through direct experience.   

Build confidence. A positive attitude from the student is vital.  The student needs to have confidence in their ability to master the material.  They also need to have confidence and in the course material and the presenter.  They want to be assured that they haven’t missed anything and that help is at hand when they need it.   Anxiety is itself a distraction (contributing to cognitive load) and can be a multiplier of any other extraneous load.   It’s important to look for signs of stress and anxiety and provide support and scaffolding where necessary.

Use plain and direct language.  Learners should not have to unpack convoluted long sentences.  Self-indulgent verbosity is perhaps the worst crime but carelessly constructed and ambiguous wording also presents problems.  Specialist terminology can and indeed should be used where appropriate but you should be confident that all the students are at a level that they understand it easily. 

Be aware that processing language is cognitively demanding.  Language is such an essential part of our human culture that we largely take it for granted but it is one of those background tasks that our working memory has to do and it chews up a lot of our processing power.   Don’t expect students to process spoken language and written language at the same time.  Limit the text in any presentation to headings and subheading or for emphasis.  Similarly, attempting to take notes while listening to a presentation is going to impact on the quality of learning.    

Clear layout and structure are important.     Use headings and sub-headings with written material to create a hierarchy of significance and make it easy for learners to find what they need to know.  Avoid big slabs of text.  Use fonts that are easy to read and leave enough white space so that it doesn’t feel cramped and constricted.  Oral presentations should follow a logical sequence and keep the audience orientated.    

Be selective and strategic about what you present (and when).   I could have started this article differently.  “In 1988 John Sweller published his landmark paper Cognitive load during problem-solving: Effects on learning which drew on earlier work in cognitive science by  G.A. Miller in the 1950s…” but this information about the academics is not germane information for the purpose of this article and is only going to distract the general reader who the article is written for.

There are:

  1. things that are important for the learner to know now.
  2. things that they will need to know in the near future but would be confusing in the current context. 
  3. things that it would be nice for them to know because it adds richness and interest (after all you cannot strip everything out so that it becomes bland and uninteresting).
  4. things that they should know already and don’t need to be explained.
  5. things that are irrelevant

It is often difficult to identify and classify what’s what.  A lot depends on the purpose of the learning and relative expertise of the learners.   For beginners and less advanced students, it’s primarily about understanding the fundamental principles and purpose and anything else is going to be a distraction.   Learning material should be specific for the level of expertise.  In the early stages, the important thing is to keep the student focussed to what is essential to the subject and what is going to be interesting to them.  The more advanced students become in an area, the more that they will be consolidating this fundamental knowledge and you should draw on more advanced examples and exercises to stretch them and help integrate their knowledge more fully.     

If there is material that you think will be of interest to the student but might trip them up then up or distract them, separate it out and put it in a sidebar or have it as a separate handout.

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