This article was written for SecEd magazine and first published in September 2017. You can read the original version on the SecEd website here.
You can access the full archive of my columns for SecEd here.
This is part six of a 10-part series. Catch up with the series so far.
Last time I argued that, if we want our pupils to learn anything (by which I mean, encode information in their long-term memories), then we need to engage their active attention and get them thinking hard. We need to give them work to do that’s challenging but achievable, because if the work’s too easy pupils will complete it through habit, but if the work’s too hard pupils will be unable to complete it. In both cases, learning will fail.
But to help pupils think hard, we need to teach them how to cheat the limited space in their working memory in order to avoid cognitive overload. In other words, we need them to think hard but efficiently.
Whereas long-term memory is practically limitless – we can keep filling it for a lifetime and never run out of space – working memory is very limited. What we get when we are born is what we’re stuck with for the rest of our lives. We can’t increase it, no matter how much so-called “brain-training” we do. And a lack of space in working memory is a functional bottleneck – when we hit the point of cognitive overload, we stop thinking and learning fails. However, there are ways to cheat this limitation…
Let’s consider the example of tying our shoe laces. At first, tying our laces requires our full attention and thus absorbs all of our working memory, but with practice we can tie our shoes automatically while our working memory is otherwise engaged, for example by having a conversation. The same rules apply to learning in a classroom environment.
Take for example learning to read. Once we have mastered reading in the sense that we know the sound each letter makes and how letters combine to make words, we still keep practising our reading not just to get faster at reading but in order to get so good at recognising the letters and words and the sounds they make that word recognition becomes automatic.
We see words and understand them and how they sound without having to think about it and this automaticity frees up precious space in our working memories which we once had to use in order to retrieve sounds and meanings from our long-term memories but which we can now devote to thinking about the meanings of sentences and texts.
Eventually, we get so good at reading that we have enough working memory to be able to recognise allusions and make other connections between the text we are reading and all the background knowledge we already possess.
What’s true of reading is true of all the skills our pupils use in all the subjects we teach.
In short, there are ways to making some processing activities automatic so that they bypass – or at least limit the space needed in – working memory, and thus free up space for more complex tasks. We’ll explore some of these in a moment, but first let’s define working memory then examine just how limited it is.
Working memory and cognitive overload
Our working memory, also called short-term memory, is used to perform mental tasks. For example, we use working memory to retain the meaning from the beginning of a sentence so that we can combine it with the end and thus understand the sense of the whole sentence.
We use working memory to help us perform mathematical equations, for example we use it to carry digits over from the single digits column to the tens and hundreds when adding up. We also use working memory to help us plan ahead and organise our actions. For example, we will use it to help us decide the order in which we clean the house or combine raw ingredients to make a meal.
George Miller, in a 1956 paper, said that “the magical number” of meaningful items or chunks the average person can hold in their working memory was “seven plus or minus two”. This has since become known as Miller’s Law.
Miller argued that we can repeat back a list of no more than about seven randomly ordered, meaningful items or chunks (these items could be letters, numbers, or whole words).
However, subsequent research has produced different results. According to Gilchrist, Cowan, and Naveh-Benjamin (2008), young adults can only recall between about three and four longer verbal “chunks”, such as idioms or short sentences.
Others have simply concluded that the limits of working memory depend on the type of task being performed, the person performing the task, and other environmental factors.
Cognitive load is the amount of mental effort it takes to do a task. There are three types of cognitive load needed for every task:
- Intrinsic load: This is the amount of mental activity involved in actually performing the task. For instance, in working out a maths problem we must follow a number of mathematical procedures. This effort is intrinsic to the task itself.
- Germane load: This is the amount of mental effort involved in trying to understand the task or material. For instance, if I read an unfamiliar text, much of my effort would be focused on trying to make sense out of it.
- Extraneous load or the immediate environment: This is extraneous to learning the subject or doing the task at hand, and is about dealing with the instructional context in which a task is being taught or performed. Disorganised instruction, for example, contributes extraneous load to a task.
Every kind of learning involves a combination of these three sources of mental effort. How we balance the three is the trick to cheating working memory.
Our capacity – and indeed our pupils’ capacity – to process information is, as we have already seen, limited. People can manipulate only a few pieces of information at any one time. Pupils are often asked to take in large amounts of new information that exceed their processing capacity, resulting in cognitive overload which, in turn, causes learning to fail. However, we can improve our pupils’ capacity for learning by managing and reducing the cognitive load required in our lessons. So, here are some strategies for reducing cognitive load.
As I say above, we can hold between five and nine meaningful items in working memory at any one time. We can help improve the usefulness of these items by combining several separate ideas into one item. This is called “chunking”. For example, if I asked you to memorise the following list of letters…
X D H
P E S
C G E
F D V
T I C
B B X
…you would need 18 spaces in your working memory to do so and so would be unable to complete the task. But if I were to ask you to memorise this list instead…
B B C
I T V
D F E
G C S E
P H D
…I bet you’d fare better than on the first list because you’d be able to chunk various letters into single items. And yet both lists contain the same number of letters (18) and, what’s more, both lists are identical albeit for the fact the letters are given in reverse order the second time around.
So why, given that the information you’re required to remember is identical, is the second list easier to memorise? Well, it’s because you were able to use your prior knowledge to combine separate items into single units, thus reducing the space required in working memory.
Because, for example, you know what the BBC is (a media organisation), you were able to chunk the three letters B, B and C into one item thus reducing the space required in working memory from three to one. The same applies to GCSE which you know is a type of qualification and so you could reduce the space required to memorise this line from four to one, using only a quarter of the space.
Rather than 18 items, you could manage with six if you consider the Xs at the beginning and end as one item.
You could also improve your memorisation of the first list by chunking information in other ways. For example, you could invent your own mnemonic to help you cheat the limited space available in working memory, perhaps using the first letter in each line to create an acronym, or you could use the “loci” method made famous by the Sherlock Holmes novels by placing the letters – perhaps represented by household objects – into memorable locations within your mind palace. You could also put the letters to song to help you through rhyme and rhythm.
In the classroom, this means we need to think of ways of reducing the amount of information pupils are expected to remember at any one time. We can teach in chunks and pause between ideas or topics.
We could also present information in ready-made mnemonics such as AFOREST (which is a mnemonic used in English to help pupils remember what to include in a piece of persuasive writing).
We could also make explicit the transitions from one topic to another, and make explicit references to how ideas and topics are related to one another. And we could make sure we teach in a logical sequence so that pupils can place new learning within the context of what they already know.
Talking of which…
Another way to help pupils cheat the limited space in their working memory is to connect new information with pupils’ prior learning because it is easier for pupils to make sense of new information when it is clearly related to what they already know and can do. Large amounts of unfamiliar material automatically increases cognitive load.
By connecting new learning with old, we help reduce the germane load, allowing more space for intrinsic load. This means drawing links, perhaps through the use of metaphor and analogy, and relating new ideas to pupils’ own life experiences, and hobbies and interests.
The use of worked examples can also be helpful in reducing germane load because they provide support that simplifies complex tasks. Worked examples and writing frames scaffold complex tasks in much the same way as stabilisers help children learn to ride a bicycle – they provide support so the novice can learn to pedal, steer and brake without also having to concentrate on maintaining their balance.
Once these aspects of cycling become familiar, there is more space in working memory to concentrate on balance and the training wheels can come off. Using a worked example or writing frame involves making the entire solution available so the pupil can explore different aspects of the problem without holding all its various parts in working memory.
And finally, we could remove all irrelevant information – thus reducing the extraneous load – so that pupils need focus only on the information that matters.
Well-organised information is better understood and remembered. Irrelevant material poses problems for pupils because they don’t always know that it is irrelevant or tangential and so devote unnecessary mental effort to trying to connect it to the topic at hand.
We should therefore try to reduce extraneous material or move it into a designated part of the lesson where pupils understand that it is not critical information.
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