Using Cognitive Load Theory to improve slideshow presentations

In recent years, the slideshow presentation has become so ubiquitous in our schools that it has become rare to walk into a lesson and not see one on display. However, teaching from a slideshow can either support or hamper learning, depending on the slideshow design.

In my English classroom, I use slideshows for a number of practical reasons:

• to present pre-prepared examples, models and images
• to provide permanent access to task instructions and success criteria
• to prompt me about what to cover next
• to share and store resources effectively and efficiently.

Unfortunately, the way that slideshows are sometimes designed – overflowing in a chaos of words and images – does not complement what we know about how people learn. 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 three and five for young adults, depending on the difficulty of the task – and there are differences in capacity between individual people (Cowan, 2010). When the capacity of our working memory becomes overloaded, it becomes harder to transfer new information into long-term memory.

Susan E. Gatherscole and Tracy Packiam Alloway (Gathercole and Alloway , 2007) note the stark differences in working memory capacity 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.

Cognitive load theory has developed from the work of Australian educational psychologist John Sweller (Sweller , 1994). It is based on understanding 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.

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, while understanding the workings of the human respiratory system has more intrinsic load than knowing where the lungs are situated in a human body.

Extraneous load is bad for learning because it can hinder the construction of long-term memories. It refers to 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.

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.

What follow are some very practical tips that I have been using in my lessons for doing just this:

Less is more. Reduce the amount of text and diagrams to as few as necessary, but no fewer. This will ensure that you do not overload your students’ limited working memory capacity.

Ensure that labels are integrated into diagrams and ensure that information is presented in close physical proximity to related information. This way, students can look at text and images simultaneously. This helps to avoid the ‘split-attention effect’, which occurs when learners have to mentally integrate information by holding one thing in working memory while they search for another (Chandler and Sweller , 1992).

Avoid reading out text that is already written on the slide (unless you think that students are unable to read it independently). Studies have shown that you should avoid reading aloud text that is written on the board or a slide. This overloads working memory because students cannot process two types of language input simultaneously.

Remove distracting or superfluous images. Only use those that directly support learning, because unnecessary images create extraneous cognitive load.

Use images to support complex and conceptual ideas. The dual coding theory suggests that presenting language and images together enhances learning (Paivio , 1971).

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). Again, this can create extraneous load.

Never expect students to read something from the board while you are talking at the same time! It is not possible to split attention between both.

Reveal processes stage by stage on the same slide, rather than on consecutive slides. This way, students have a prompt to remind them of earlier stages and do not have to juggle too much information in working memory.

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