Claire Badger, Senior Teacher, Teaching and Learning, The Godolphin and Latymer School, UK

Sweller’s cognitive load theory (CLT; Sweller et al., 1998) has been described as a theory that teachers really need to understand (New South Wales DoE, 2017) to teach effectively. The theory has been summarised elsewhere (e.g. Kirschner, 2002; Tharby, 2019; Boxer, 2018) but the key implication for teaching is that we should maximise the amount of working memory that is dedicated to transferring information that is being learned to long-term memory (germane cognitive load). We can do this by ascertaining the level of prior knowledge of our students (in order to accurately assess the level of intrinsic cognitive load of the learning task) and by designing instructional experiences to minimise extraneous, non-productive cognitive load. This article describes how I have applied these principles to my A-level chemistry teaching.

Presenting new material

The use of worked examples is recognised as being highly effective for teaching novices. However, the ‘expertise reversal effect’ means that this becomes less effective for more knowledgeable students and may actually hinder learning (Sweller et al., 2019). A significant proportion of A-level chemistry is mathematical and builds on GCSE calculation work. I used to start the course re-teaching much of the GCSE calculations through worked examples; now I begin with a baseline test to ascertain students’ prior knowledge. This gives me a more accurate assessment of the intrinsic load that will be experienced by my students when learning from the material, allowing me to adjust my teaching accordingly. The rationale behind giving a ‘test’ at the beginning of the course was explained to the students and they responded positively, acknowledging that this would also allow them to assess for themselves which aspects of the GCSE material they needed to revisit.

CLT can be used to improve slideshow presentations, for example, by reducing the amount of text on slides and removing distracting or superfluous images (see Tharby, 2019). I have consciously made an effort not to read out what is written on the slides when teaching but, instead, to give time to students to read themselves, or alternatively show only keywords or a diagram, placing the original text into the speaker notes.

In the past, I used to introduce worked examples via a PowerPoint presentation, flashing up the next steps as I talked through how to approach a calculation. This imposed extraneous cognitive load on students, as they were desperately trying to copy down the example as well as listen to my explanations. I now explicitly tell the students to put their pens down whilst I am talking and hand-write the examples on the board, which slows down my explanations and models my own thought processes (see EEF, 2018). I often record these explanations (Badger, 2019), a strategy that has proved particularly effective as we have switched to remote learning due to the coronavirus pandemic.

Consolidation exercises

A feature of the linear A-level course is that students need to make links between different topics; this also entails them understanding where connections are not appropriate. CLT suggests that a combination of words and images, dual-coding, is more effective for learning (Paivio, 1971), so in order to address these issues, I used graphic organisers (Caviglioli, 2019, p. 50); the ‘chunk and compare’ graphic organisers seem to be the most pertinent to A-level chemistry. In one activity, I designed a Venn diagram sorting activity with two categories: attraction between electrons and the nucleus, and charge density, concepts that students often confuse. I provided students with descriptions of trends, for example the oxidising ability of the halogens and the strength of ionic bonding, and asked them to place them in the correct place on the diagram. I also included two examples that did not go in either circle. Students were asked to explain their reasoning as they completed the task and it proved particularly helpful in unpicking students’ misconceptions and confusion between these two topic areas.

Student responses

I made these changes to my teaching over the course of an academic year and planned to evaluate the impact by investigating to what extent students used ideas from CLT when revising for their practice examinations. However, due to COVID-19, we switched to remote working, and so this evaluation was limited. Nevertheless, I sent out a survey to all my Key Stage 5 classes (29 students in total) to garner their opinions on the activities described above. The survey asked students about their awareness of CLT and to rank the teaching and learning activities described above on a five-point scale, from extremely useful to extremely detrimental, as well as giving space for further comments.

Twenty students responded, a quarter of whom said that they had never heard of cognitive load theory, with the rest evenly split between having a reasonable grasp of the key points and an awareness but not sure how it translated to their learning. Despite this, students indicated that they found the activities described above useful; including images and modelling thought process were ranked highly by all students, with graphic organisers rated as extremely useful or mostly useful by all bar one. These same strategies were ranked as being useful for their own learning and were used when preparing for practice examinations. Interestingly, although half of the students stated that they found creating a voice-over useful for their learning, only five students actually used this technique. This could in part be explained by the fact that Year 13 in particular did not prioritise revision, with one saying, ‘I wanted to take a break from school so I mainly read over some notes to refresh my memory on the topic’, which seems reasonable under the circumstances, and another saying that she talked through explanations but didn’t necessarily record this.


Drawing firm conclusions from this small-scale study should be undertaken with a great deal of caution, particularly given the lack of formal end-of-year examinations or available comparisons with previous cohorts. Student responses refer only to their perceived learning and not their actual learning, and students are often poor judges of what makes effective learning. Nevertheless, the positive student feedback indicates that it is worth continuing to take cognitive load theory into account when planning my chemistry teaching. It seems more important that teachers understand how CLT can be applied to teaching rather than students themselves having an understanding of the theory. A further takeaway is that tasks using CLT principles, e.g. recording voice-overs and using graphic organisers, need to be set explicitly, as students appear less likely to do this independently despite finding it useful for their learning.


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