Cognitive overload

Cognitive Load Theory (CLT) and classroom practice

For IB Geography teacher, Elen Harris, understanding CLT can enhance effective student learning, especially when introducing and developing a new topic, concept or idea.

What is Cognitive Load Theory?

 Cognitive Science (CogSci) explores how the brain encodes and stores information, transferring it from working to long-term memory Fletcher-Wood et al., 2019). Cognitive Load Theory (CLT) (devised by Sweller in the 1980s) is a strand of CogSci which demonstrates the potential for working memory overload and suggests teaching methods to minimise overload so students can learn complex ideas (Enser, 2019a).

According to Weinstein et al. (2018) ‘few teacher training textbooks cover’ CogSci principles, though there has been an ‘increased interest in the potential of cognitive science to inform classroom practice’ (Scutt, 2019) in recent years, especially as teaching becomes a more evidence-informed profession.  In a 2017 Tweet, Wiliam asserted that CLT is the ‘single most important thing for teachers to know’ (Enser, 2019a). Given this, how should we be mindful of it in our everyday practice?

Working memory under pressure

In order to optimise learning and to enable us to think, working memory has to perform efficiently. However, it can become cognitively overloaded:

  • The ‘intrinsic load’ is affected by task complexity (difficult or unfamiliar material equals a higher load (Tharby, 2019)).
  • The ‘extraneous load’ involves thinking that hinders learning, e.g. when dealing with overly-complex slide design (Enser, 2019a).
  • The ‘germane load’ is the desirable load that contributes to learning (Tharby, 2019).

The extraneous load should be reduced as far as possible because it gets in the way of learning. However, the intrinsic load should be managed, ‘but not necessarily reduced’ as ‘memory is the residue of thought’ according to Wiliam (Young, 2014), as you remember more of what you actively think hard about (McCrea, 2019). Reducing extraneous load and managing intrinsic load will benefit germane load and lead to better learning.

Using ‘Faded Scaffolding’

At the start of a topic, intrinsic load is high as students are novices and have few prior schemas (networks of information in the brain) to draw from in their long-term memory. They will benefit from simple to complex sequencing of taught material to reduce cognitive load. Therefore, carefully sequenced helix curriculum design is important for students to ‘hook’ new knowledge onto existing schemata to optimise learning (Deans for Impact, 2015). Within lessons, tasks should be delivered using a fading scaffolding continuum from ‘worked-out examples to completion assignments (where a partial solution is given and they have to complete it themselves)’ to independent answers (Shibli & West, 2018).

For example, a model answer could be provided by the teacher, then a partially completed writing frame done together, before students have a go at independently answering a question. Faded scaffolding is more applicable in some subjects than others – it is easier to achieve in Science and Maths, for example, than in subjects like Geography, where it initially appears this principle might only apply to the likes of completing past paper questions. However, faded scaffolding does not have to be as concrete as task design – it can also apply to providing analogies and examples for abstract concepts, so its use is multifaceted.

Explicit models of instruction

CLT provides support for explicit models of instruction (CESE, 2017) and challenges the myth that ‘students learn best by discovering things for themselves’ (Enser, 2019a) and therefore contends inquiry learning. Independent research tasks and inquiry learning take up valuable space in working memory (Wiliam, 2018) as students may be overloaded by simply working out what to research (Kirschener & Hendrick, 2020).

Research tasks have merit if the aim is to explicitly teach research skills, but if a research task is merely a method of content delivery it is important to ensure it is correctly scaffolded. Care is needed though, as Watson (2020) outlines how CLT can encourage an ‘overemphasis on teacher-led instructions’ as opposed to student-led learning.

Reducing extraneous cognitive loading

Tharby (2019) recommends reducing extraneous load by ensuring diagrams and associated information are near (the ‘multiple-modalities approach’ (Deans for Impact, 2015) to avoid the ‘split-attention effect’; that processes are revealed stage-by-stage on the same slide so students can be reminded of earlier stages; and that teachers do not read text that is on a slide to avoid the ‘redundancy effect’ (Jones, 2018) as students cannot process listening and reading at the same time. These are all things teachers can frequently be observed doing and therefore should work on to ensure students are not cognitively overloaded.

Benefits of teachers learning about CLT

CLT is a useful tool that can help guide our everyday practice – one of the most effective methods of teaching to develop deep understanding of new knowledge, is to build a student’s long-term memory, leading to successful learning. To be of full benefit, the principles need embedding into long-term curriculum planning with the creation of helix curriculums and increasingly confident use.

In one sense CLT is not new: as Enser (2019a) states, CLT just supports how ‘excellent teachers have always taught’, providing a rationale for why strategies they have adopted work and as such it is just ‘common sense’.

However, it is incredibly useful for early career teachers who have not reached expertise level, helping them to ‘leapfrog’ the trial-and-error stage (Enser, 2019b). Gaining a proper understanding of CLT ‘can improve teacher instruction’ (Shibli & West, 2018) and ensures teaching is ‘at the appropriate level of challenge’ (Watson, 2020). Moreover, even experienced teachers will benefit from learning about CLT and other CogSci principles: there is no doubt, if you ‘know and understand the theories behind your practice’ you can ‘optimise your teaching’ (Kirschner & Hendrick, 2020).


Elen Harris teaches Geography at Sevenoaks School, where she is a research fellow at the Institute of Teaching & Learning.

More information on this study together with other articles can be found in Innovate, the annual academic journal from the Institute for Teaching and Learning at Sevenoaks School:



Feature Image: by sallen666888 on Pixabay

Support Image: kindly provided by Sevenoaks School


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