Tag Archives: Dual Coding

Understanding what you don’t know: dual-coding, cognitive load, and using diagrams in explanations

So, full disclosure, I’m no expert in either dual-coding or Cognitive Load Theory. Actually, I am really not an expert in many of the issues I will be covering in this blog post. But that’s ok. In fact, in many ways, it’s desirable because, as teachers, we have to interact with so much information on a daily basis that it is simply not possibly to become an expert across so many different domains. When interacting with research, advice, or theories, we must attempt to take the ‘headline’ principles and apply them to our classroom practice. Some stuff we’ll get wrong; other stuff we might get right. The great thing about blogs, and also about platforms like Twitter, is that they allow the flow of ideas to be shared, refined, discussed, and critiqued.

For Cognitive-Load-Theory I’m going to take this from Dan Williams as my ‘headline’:

“Working memory is only able to hold a small amount of information at any one time and instructional methods should avoid overloading it in order to maximise learning (Sweller, 1988).”

For my dual-coding ‘headline’, I’ll make us of what Oliver Caviglioli describes as Sweller’s “hack”:

“The amount of information that can be processed using both auditory and visual channels should exceed the processing capacity of a single channel.”

Given these explanations, it seems dual-coding is technique that allows the brain to complete additional processing, sort of like a processor upgrade in a computer, to partially overcome the limitations of working memory. No doubt this is true, but when I reflect on how I use visuals in my teaching of English, it occurs to me that I use them for the opposite reason: to decrease cognitive load, rather than produce increase in overall cognitive capacity.

For example, when teaching ‘Bayonet Charge’ recently, I felt would be useful for my pupils to have an understanding of what ‘no man’s land’ is. Were I to have stood in front of the class and explained the concept to them, I might have said something like this:

“In World War One, armies generally fought in long trenches. Imagine a field with two trenches dug parallel to one another; one army is in one trench trying to advance east while the other army is in the other trench trying to advance west. There is a gap of land between them that no one owns. This is called ‘no man’s land’ because it belongs to ‘no man’.

While some pupils may grasp the concept, many will not. This is not because they are incapable of understanding the concept but because there are many bits of information they must remember: WWI, trenches, a field, parallel lines, east and west advances, a ‘gap’ of land. Another problem is that I am trying to explain something visual, but since I am attempting to explain where certain things are located in relation to one another, the explanation comes across as quite technical. I can hardly be said to have “painted a picture” in their minds. Further, I’m asking them to apply mathematical and historical knowledge to a poetry lesson in an English classroom. So, clearly, there is a number of potential pitfalls here, and I am expecting them to simultaneously hold and manipulate multiple pieces of information.

And yet, by simply drawing a crude diagram, I can negate most of these pitfalls:

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For me, the beauty of the diagram isn’t so much that it allows extra information to be processed, as advanced by the definition of dual-coding above (although it may do that), but rather that it releases pressure from the pupils’ working memories. I would begin with a blank white board and add to the diagram piece by piece as I explain the concepts, thus freeing the pupils’ to fix their attention on the upcoming piece of information rather than using it to hold onto the last piece of information; in effect, the diagram performs the role of long-term memory and, in the process, frees up working memory. Hopefully, when the explanation is complete, the diagram will also allow the information to be processed and stored as a single concept, rather than as a number of disparate pieces of information that must be pulled together.

Let’s look at one another example. This time capitalism. When studying texts such as ‘An Inspector Calls’ or ‘Blood Brothers’, I might consider it useful for pupils to have some understanding of capitalism. While I could tell them something like: “capitalism is an economic system in which private individuals own companies and employ workers to make a profit,” this alone doesn’t cut the mustard; there are problems with this explanation. Do the pupils know what “capital” is? How many will know what is meant by “economic system”? What about “private individuals” or “profit”? Et cetera. But actually, even before we get to the point of defining capitalism or the constituent parts of knowledge that are required to understand the definition, I think it is useful for pupils to first have an understanding of how capitalism works.

Again, to illustrate this, I can use a combination of explanation and diagram:

“Mrs Builder has £1,000,0000 from a job she has just completed. For save keeping, she gives it to Mr bank. Now Mrs Builder still has £1,000,000 but Mr Bank also “has” £1,000,000.”

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“Along comes Mr cake, who wants to open a cupcake shop. He asks Mr Bank if he can borrow a £1,000,000 to set up his business. Mr Bank agrees, but says Mr Cake must pay back £1,100,0000. Mr Cake now has the £1,000,000 and the bank “has” £100,000 (owed in interest).”

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“Next up, Mr Cake employs Mrs Builder to build his cupcake shop. Mrs Builder charges him £1,000,000. Mr Cake now has £1,000,000 of assets. Mrs Builder, who now has £2,000,000, places the £1,000,000 Mr Cake has paid her in the bank. The bank now has £1,000,000 of deposits and £100,000 of interest owed.”

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“Unfortunately for Mr Cake, halfway through the job Mrs Builder realises she has severely underestimated the cost of building the cupcake shop, as builders are likely to. She charges Mr Cake an extra £1,000,000 to complete the job. Mr Cake is not happy but he can hardly stop now, so he goes to the bank, who again approve his request and again charge £100,000 in interest. Mr Cake now has £2,000,000 worth of assets, the bank £200,000 of interest owed, and Mrs Builder £3,000,000.”

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“Finally, Mrs Builder also puts this additional  £1,000,000 into the bank.”

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Now, clearly this is a gross oversimplification of how a modern capitalist economy actually functions, and the pupils may ask a series of follow-up questions (“what if Mrs Builder wants all her money back at once?”), so if you’re going to explain this you must anticipate those questions and know the answers. However, it does give a nice example of how capitalism uses credit, and the idea of future earnings, to turn money into more money (useful for ‘Blood Brothers’). In this case, £1,000,000 has been “turned into” £6,200,000. Mrs Builder has £3,000,000, Mr Baker has £2,000,000 of assets, and Mr Bank has £200,000 owed in interest from Mr Baker and £1,000,000 of Mrs Builder’s money, which it can invest elsewhere. In the future, assuming Mr Cake pays his debts, Mr Bank will also be able to re-invent this £2,000,000 in other ventures, turning it into yet more money. From here, it will be easier to have conversations about things such as “capital” “investment” or “bosses v workers” (useful for ‘An Inspector Calls’) as pupils have an idea, albeit very basic, of how a capitalist economy works. If you use Mr Cake or Mrs Builder as illustrations of bosses, then a discussion of bosses v workers feels more concrete than simply saying they are a part of “an economic system in which private individuals own companies and employ workers in order to make profit.” The pupils may well never use the precise knowledge gained  in an essay on BB or AIC, but they may well become more confident and coherent when discussing capitalism and its surrounding issues in the texts.

However, my point here is not really about the discussions this knowledge may lead to. Again, it is about how the diagrams facilitate understanding. If I had explained the process without the aid of diagrams, it is highly unlikely that any pupils would have grasped what I had said, because the volume of information is simply too large. Again, the diagrams stand in place of long-term memory, freeing-up working memory to understand and follow the explanation.

(Just in case you’re wondering, banks operate on the premise that not all of their depositors [people or organisations who deposit money] will want to withdraw their money at the same time. It was, in part, this assumption that caused Northern Rock to fail, as, all at once, its depositors lost confidence in the banks’ ability to pay them their money. Thus they simultaneously withdrew their funds, creating a self-fulfilling prophecy. This is also what happens during the bank scene in Mary Poppins.)

Lastly, I want to touch on how I explain Browning’s use of irony in ‘My Last Duchess. I have previously blogged about this, so I won’t give another blow-by-blow account. (You can download the resources here, should you wish.) In short, what I do is talk the pupils to a point whereby they understand that there is a gap between what The Duke says in his monologue and what it is that the reader is supposed to understand from his words. The Duke says one thing and the reader understands this. But the reader also understands that Browning, the poet, is using The Duke’s words to tell us something opposite. We end up with this diagram:

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I recently read an extremely enlightening blog by Clare Sealy, in which she investigated knowing and understanding and pointed out that they are more interlinked than people often assume. Traditionally, the debate has focussed upon whether knowing is enough and whether memorising information alone can be said to produce understanding. The implication is that knowing (or memorising) is the grubby second-cousin of true understanding, and this model of thought naturally assumes that knowing/memorising comes before understanding.

But what I touched on in my previous post about ‘My Last Duchess’, and what Cognitive Load Theory and dual coding make clear, is that it is possible to understand something without ‘knowing’ it. That is, without having committed it to long-term memory. This flies in the face of much of what is said about memorisation — which is often claimed to be superficial. But sometimes, if we take the time to give pupils clear and cogent explanations, with diagrams standing in for long-term memory, they can understand much more than we think. This has important implications for what we teach our pupils, as it allows us to raise the threshold of our expectations.

It might also change the nature of our instructional sequences. Were I to solely consider pupils’ prior knowledge, I might think it a bad idea to teach irony in relation to ‘My Last Duchess’. Irony can be a slippery concept at the best of times, and this might put me off teaching it in relation to ‘My Last Duchess’, a difficult poem itself, especially when pupils do not know nor understand the concept. But irony isn’t like alliteration. You can’t just explain it and then confidently expect pupils to begin identifying it — it is far too complex. To avoid confusion and misconceptions, pupils need to have irony demonstrated for them before it is defined for them, before they know the definition, and the use of diagrams allows for this; by standing in for long-term memory, diagrams allow us to reverse the knowing/understanding relationship.

Here, it is important to note that this in no way means we can do away with committing things to memory. Quite the opposite, in fact. How can I be so sure? Well, I have taught the lesson on irony in ‘My Last Duchess’ to two different bottom set Y10s in two different schools and I’d say 90% of the pupils I explained it to understood it. You might be sceptical, but, trust me, these are not the kind of shy kids who will meekly agree that they understand if they don’t. If they are confused, they will make sure you know about it! But what was interesting was as soon as I used the blank screen function on the interactive whiteboard to take away the diagram (i.e., to remove the crutch that functions as “long-term memory”), the pupils could not parrot back to me what I had just explained, what they had just understood, and what they could parrot back when the diagram was displayed.

Unsurprisingly, the pupils found this highly frustrating. But they were frustrated because they understood, not because the didn’t. They were frustrated because they understood the concepts but the mental architecture that would allow to explain what they understood had not been constructed in their long-term memories.

The clear inference is that, in a well-designed instructional sequence, not only is memorisation vital to enable pupils to demonstrate what they understand, but memorisation, far from being a grubby, secondary learning-goal, can sometimes be the harder and more advanced learning process; it is not shallow, dry, surface, or disembodied, but effortful, useful, and the ultimate goal of education, because it is memorisation, the ability to recall information at will, that allows that information to be used at the moment it is required. Memorisation allows performance, is a pre-condition for long-term performance, and, without it, understanding cannot be made visible.