Using cognitive load theory to improve slideshow presentations

Written by Andy Tharby

In recent years, the slideshow has become so ubiquitous that it has become synonymous with the lesson itself. ‘I just need to finish planning this lesson’ has come to mean ‘I just need to complete slides 56 and 57 of my PowerPoint slideshow.’ However, the jury is still out as to whether teaching from a slideshow supports or hampers learning.

Perhaps the most pertinent advice on this matter comes from the 1980s British female pop music vocal group Bananarama: it ain’t what you do (it’s the way that you do it).

Teachers usually find slideshows to be useful for:

presenting pre-prepared examples and models;
presenting images and videos that support learning;
providing the class with permanent access to task instructions and success criteria;
providing prompts to remind the teacher about what to cover next;
sharing and storing resources efficiently.

In this post, we shall consider how to improve slideshow design by looking towards the findings from the research into the human working memory. Our working memory, which we use for language comprehension, problem solving and planning, has a very small capacity. We can only hold on to a limited number of items at once – between 3 and 5 for young adults depending on the difficulty of the task – and there are differences in capacity between individual people.

Susan E. Gatherscole and Tracy Packiam Alloway (2007) note the stark differences that can occur in the average class:

“… in a typical class of 30 children aged 7 to 8 years, we would expect at least three of them to have the working memory capacities of the average 4‑year-old child and three others to have the capacities of the average 11-year-old child which is quite close to adult levels.”

Working memory capacity difference, therefore, is one of the main reasons why some students learn less than other students from the same teacher input. However, we should also remember that the working memory capacity of all humans is very small, even those with a larger than average capacity.

Cognitive load theory is based on the types of information held in working-memory at any one time. These are known as intrinsic load, extraneous load and germane load and, added together, make up the capacity of the working memory. Cognitive overload occurs when the capacity of the working memory is exceeded.

Intrinsic load is related to the inherent difficulty of the subject matter being learnt. It is influenced by how complex the material is and how much a student already knows about the topic. For example, 2 + 2 + 4 has less intrinsic load than 93 x 543, whereas understanding the workings of the human respiratory system has more intrinsic load than knowing where the lungs are situated in a human body. Intrinsic load is fixed and unchangeable – although there are some nifty ways of helping to reduce its influence.

Extraneous load is bad for learning because it can hinder the construction of long-term memories. It is any extra and unnecessary thinking that students have to do that does not contribute to learning. Unlike intrinsic load, extraneous load is related to how the subject material is presented rather than its inherent difficulty and, as teachers, we can either heighten or reduce its effect. Unfortunately, many teachers remain unaware that the design of their slideshows actively increases extraneous load.

The third type of cognitive load, germane load, is desirable. It is the load placed on working memory that contributes directly to genuine learning. In other words, the nourishing and productive thinking that causes our students to form and consolidate long-term memories.

Therefore, a good slideshow presentation should:

Remain mindful of the intrinsic load of the task;
Reduce extraneous load;
Increase germane load.

Here are some very practical and evidence-informed tips for doing just this (please follow the links and references at the bottom of the page for more detail):

Less is more. Reduce the amount of text and diagrams to as little as is necessary. It may seem counterintuitive, but when students are working with new and complex material, the more jam-packed your slides, the less likely they are to learn.

Ensure that labels are integrated into diagrams so that students can look at text and images simultaneously.

Remove distracting or superfluous images. Only use those that directly support learning.

Use arrows to show connections between text and diagrams.

Use colour-coding to show the relationships between connected ideas – avoid too many colours though.

Ensure that the information is presented physically close to related information.

Use images to support complex and conceptual ideas. The dual coding theory suggests that presenting language and images together improves learning.

If you intend to explain an image, it is best not to include written text at the same time (especially when you intend to be brief).

Avoid reading out text that is already written on slide (unless you think students are unable to read it independently).

Never expect students to read something while you are talking at the same time!

Reveal processes stage-by-stage on the same slide, rather than consecutive slides.
This way, students have a prompt to remind them of earlier stages and can catch up if they lose concentration for a moment.

Remember that spoken words and slides are fleeting and transient and that your students’ innate cognitive architecture means that they will be unable hold on to them all at once. Slide-show handouts and directed note-taking can reduce this problem.

If you do one thing after reading this blog, then may we suggest that you watch these two videos on Richard E. Mayer’s Cognitive Theory of Multimedia Learning, which is closely linked to cognitive load theory. The first covers the theory; the second covers five practical principles for reducing extraneous load.

Further reading

The Split-attention Effect as a Factor in the Design of Instruction – Chandler and Sweller (1992)

Managing Split-attention and Redundancy in Multimedia Instruction – Kalyuga, Chandler and Sweller (1999)

The Magical Mystery Four: How is working Memory Capacity Limited, and Why? – Cowan (2010)

Understanding Working Memory: A Classroom Guide – Gathercole and Alloway (2007)

Cognitive Load Theory: Research that Teachers Really Need to Understand – Centre for Education Statistics and Evaluation, NSW (2017)