It is a self-evident truth that the role of teachers is to facilitate student learning. For students to learn anything there needs to be a change in their long-term memory (Kirschner et al., 2006). The problem is that no one really understands what memory is or how to define it. But undeterred I am nonetheless going to start with a simple model of how memory works and based on what we do know about memory I will then look at how spaced practice, low stakes testing and design of our curriculum can help with long-term memory retention.
There is a simple model of memory that splits memory into two components: long term memory and short term memory (Wallingham). Our short term memory directly interacts with the environment through our senses and act as a kind of filter that determines what new learning needs to be stored in long term memory. The problem with our short term memory is its capacity is rather limited (but I'll write about more about this in a future post). By contrast our long-term memory is vast. Although we observe our environment, we do not remember everything coming in via our senses. If you want to see an example of this effect then consider what happens when you make a journey for the first time. You cannot hope to learn all the landmarks, road names and so on, which means making the return journey from memory alone very difficult. When we learn something well, perhaps we have made the same journey half a dozen times, we can retrieve this knowledge from our long-term memory to help us navigate the route.
Robert Bjork proposes a framework for storage and retrieval strength of long term memory that we need to consider. Retrieval strength considers how easily something is retrieved right now so a low retrieval strength might require some effort of thought to dig that knowledge out. Storage strength refers to whether something is well learned. That is can we retrieve the knowledge at a later time or at least can we relearn something more easily than the first time round? Lets look as some concrete examples. Knowledge that has high storage strength and low retrieval strength might include something I learned years ago in school. From memory I am able to recite some of William Shakespeare's Julius Caesar that my English teacher forced me to learn some 20-odd years ago! And to demonstrate it, here is a speech by Brutus the assassin that I promise I am recounting from memory and not cheating by looking this up: "Friends, Romans, Countrymen lend me your ears I have come to bury Caesar not to Praise him ..."
Something that has high retrieval strength and high storage strength means that I am having constant and repeated exposure to that knowledge and I can retrieve it with little effort of thought. This is basically how marketing and advertising works. That is constant repetition of a very simple message, which means we all easily recognise the logos of big brands. Each day I drive past a MacDonald's bill board on the way to and from work. Therefore each year I am literally exposed to this message hundreds of time. And this is a single advert. Think of all the adverts I am constantly exposed to on TV, Radio, bill boards and web. Its a good job I have a vast long term memory to store all this!
Retrieval and storage strength in long term memory
It is desirable that some memories are not retained. For example, I go to the supermarket and I can remember where I parked the car. However ask me a week later where I parked and I will have no idea. Retaining this information is useless to me and so I forget it. Therefore this memory has a high retrieval strength but a low storage strength.
How does this help us to understand us what is going on when teaching students? When you test students immediately on their learning, perhaps in a plenary at the end of a lesson, they may perform well. Test them some time later and they perform less well. While this is to frustration of many teachers, it is clear that pupils have forgotten what they learned in the intervening time. What is going on here is that pupils' learning had high retrieval strength, but poor storage strength. How then do we ensure that children are well prepared for their exams and more importantly for life by ensure that what they learn sticks? Well the answer is to repeatedly expose the pupils to the learned content.
All this brings us nicely on to the Ebbinghaus Forgetting curves. In 1885 Ebbinghause carried out some experiments on himself where he learned a sequence of letters then tried to remember those sequences after various periods of time. What he concluded was that the longer the period of time between learning and recall the more he forgot. However the more he reviewed the material in subsequent days the more he remembered when tested at a later date.
We are all aware that we forget stuff over time, so the Ebbinghaus forgetting curves are an unremarkable result, nevertheless he demonstrated in a succinct way the effect that reviewing learning had on long term memory retention ie the storage strength that we have already discussed. The strength of the memory determines how steep the drop off of memory with time is. The more we are exposed to the content the less we forget over time. Another effect of this is that is it much easier for us to relearn something a second or third time than it is the first time. From this two questions arise. Firstly, what is the optimal time interval for spaced retrieval? Secondly, how many times do we have to revisit an idea before it is so embedded that we will never forget it?
Not much research has been carried out to answer either of these questions, but I suspect this will depend on the type of knowledge that we are trying to learn. However there is a study that looked at the spacing gap between studying something once then studying it again and the test delay between the second study of the material and the test (Cepeda et al, 2008).
The delay between content review and the test has a big impact on performance. Keeping this short yields the best performance on the final test. For long test delays up to 350 days the performance is poor. Think about what this means in the context of school education. When pupils learn something at the start of Year 12 for A level, they will be taking an exam some 650 days (~2 years) later. So if students have not revisited that material it is unlikely they will remember enough to perform well.
Memory over time (from Cepeda et al)
There also appears to be an optimal spacing gap. Reviewing something too soon after learning is less effective that allow a greater time delay for review. This is because not enough time has passed to allow forgetting to take place if the revision session has happened too soon. Relearning something after forgetting is more powerful as it helps build those strong neurological pathways,. So here is something totally counter intuitive: forgetting is actually helpful to learning.
By now I hope that I have convinced you that some kind of spaced practice benefits learning, even if we do not know exactly how often and how many times we should review learning. Realistically in a school environment we are constrained by timetables, school holidays and so on, so we will have to fit our spaced practice around the school structure. On a daily basis reviewing learning from the previous lesson at the start of the current lesson will help. Setting delayed homework by a week or two, and having cumulative tests (ie not just testing the previous topic, but testing all topics previously studied) are some ways we could review learning.
Once we have learned something, testing is the most effective way of making sure we consolidate that learning. It is thought the act of retrieving this information from our long term memory builds up stronger neurological pathways.
Studying versus testing (from Roediger et al)
This is demonstrated in a paper by Roediger et al. Three test groups learned some content using three different approaches. The first group only studied the material (SSSS). The second group spent most of their time studying the material, but also used self-testing to help them learn. The third group studied the material, and spent most of the time on self-testing. The three groups where then tested formally after 5 minutes. The group that only studied the content performed the best, and the group that performed worst was the group that spent most of the time self-testing. But look what happens when the formal test takes place a week later. The result is reversed; the group that spent most of the time studying performed the best. Clearly self-testing has leads to better storage strength.
Using testing for spaced practice does have its caveats and not everyone agrees on its efficacy. Most research on the topic has focused on simple knowledge (basic facts, vocabulary, rote learning). Van Gorg and Sweller (2015) stated that "the testing effect decreases as the complexity of learning material increases". What they meant by complex material referred to knowledge that showed interaction between various basic elements.
The point is is that testing is effective but we need to ensure that we are not just posing questions that require recall. We need to ask questions that require higher order thinking. Also we need to have a balance because we have a finite amount of time to deliver our curriculum and the more time we spend testing the less time we have for teaching the content and dealing with misconceptions. And actually if children fundamentally do not understand the content, no amount of testing is going to help. Below is a list of ideas that can help with space practice, some of these will be the focus of a future post:
In my subject computer science one of the elements of the KS3 national curriculum requires pupils to understand simple Boolean logic. Throughout years 7-9 pupils will come across this several times in the following topics:
I am going to leave you with a few basic principals which I hope the reader will take away:
Simple model of memory
There is a simple model of memory that splits memory into two components: long term memory and short term memory (Wallingham). Our short term memory directly interacts with the environment through our senses and act as a kind of filter that determines what new learning needs to be stored in long term memory. The problem with our short term memory is its capacity is rather limited (but I'll write about more about this in a future post). By contrast our long-term memory is vast. Although we observe our environment, we do not remember everything coming in via our senses. If you want to see an example of this effect then consider what happens when you make a journey for the first time. You cannot hope to learn all the landmarks, road names and so on, which means making the return journey from memory alone very difficult. When we learn something well, perhaps we have made the same journey half a dozen times, we can retrieve this knowledge from our long-term memory to help us navigate the route.
Robert Bjork proposes a framework for storage and retrieval strength of long term memory that we need to consider. Retrieval strength considers how easily something is retrieved right now so a low retrieval strength might require some effort of thought to dig that knowledge out. Storage strength refers to whether something is well learned. That is can we retrieve the knowledge at a later time or at least can we relearn something more easily than the first time round? Lets look as some concrete examples. Knowledge that has high storage strength and low retrieval strength might include something I learned years ago in school. From memory I am able to recite some of William Shakespeare's Julius Caesar that my English teacher forced me to learn some 20-odd years ago! And to demonstrate it, here is a speech by Brutus the assassin that I promise I am recounting from memory and not cheating by looking this up: "Friends, Romans, Countrymen lend me your ears I have come to bury Caesar not to Praise him ..."
Something that has high retrieval strength and high storage strength means that I am having constant and repeated exposure to that knowledge and I can retrieve it with little effort of thought. This is basically how marketing and advertising works. That is constant repetition of a very simple message, which means we all easily recognise the logos of big brands. Each day I drive past a MacDonald's bill board on the way to and from work. Therefore each year I am literally exposed to this message hundreds of time. And this is a single advert. Think of all the adverts I am constantly exposed to on TV, Radio, bill boards and web. Its a good job I have a vast long term memory to store all this!
It is desirable that some memories are not retained. For example, I go to the supermarket and I can remember where I parked the car. However ask me a week later where I parked and I will have no idea. Retaining this information is useless to me and so I forget it. Therefore this memory has a high retrieval strength but a low storage strength.
How does this help us to understand us what is going on when teaching students? When you test students immediately on their learning, perhaps in a plenary at the end of a lesson, they may perform well. Test them some time later and they perform less well. While this is to frustration of many teachers, it is clear that pupils have forgotten what they learned in the intervening time. What is going on here is that pupils' learning had high retrieval strength, but poor storage strength. How then do we ensure that children are well prepared for their exams and more importantly for life by ensure that what they learn sticks? Well the answer is to repeatedly expose the pupils to the learned content.
All this brings us nicely on to the Ebbinghaus Forgetting curves. In 1885 Ebbinghause carried out some experiments on himself where he learned a sequence of letters then tried to remember those sequences after various periods of time. What he concluded was that the longer the period of time between learning and recall the more he forgot. However the more he reviewed the material in subsequent days the more he remembered when tested at a later date.
We are all aware that we forget stuff over time, so the Ebbinghaus forgetting curves are an unremarkable result, nevertheless he demonstrated in a succinct way the effect that reviewing learning had on long term memory retention ie the storage strength that we have already discussed. The strength of the memory determines how steep the drop off of memory with time is. The more we are exposed to the content the less we forget over time. Another effect of this is that is it much easier for us to relearn something a second or third time than it is the first time. From this two questions arise. Firstly, what is the optimal time interval for spaced retrieval? Secondly, how many times do we have to revisit an idea before it is so embedded that we will never forget it?
Not much research has been carried out to answer either of these questions, but I suspect this will depend on the type of knowledge that we are trying to learn. However there is a study that looked at the spacing gap between studying something once then studying it again and the test delay between the second study of the material and the test (Cepeda et al, 2008).
The delay between content review and the test has a big impact on performance. Keeping this short yields the best performance on the final test. For long test delays up to 350 days the performance is poor. Think about what this means in the context of school education. When pupils learn something at the start of Year 12 for A level, they will be taking an exam some 650 days (~2 years) later. So if students have not revisited that material it is unlikely they will remember enough to perform well.
Memory over time (from Cepeda et al)
There also appears to be an optimal spacing gap. Reviewing something too soon after learning is less effective that allow a greater time delay for review. This is because not enough time has passed to allow forgetting to take place if the revision session has happened too soon. Relearning something after forgetting is more powerful as it helps build those strong neurological pathways,. So here is something totally counter intuitive: forgetting is actually helpful to learning.
By now I hope that I have convinced you that some kind of spaced practice benefits learning, even if we do not know exactly how often and how many times we should review learning. Realistically in a school environment we are constrained by timetables, school holidays and so on, so we will have to fit our spaced practice around the school structure. On a daily basis reviewing learning from the previous lesson at the start of the current lesson will help. Setting delayed homework by a week or two, and having cumulative tests (ie not just testing the previous topic, but testing all topics previously studied) are some ways we could review learning.
Once we have learned something, testing is the most effective way of making sure we consolidate that learning. It is thought the act of retrieving this information from our long term memory builds up stronger neurological pathways.
Studying versus testing (from Roediger et al)
This is demonstrated in a paper by Roediger et al. Three test groups learned some content using three different approaches. The first group only studied the material (SSSS). The second group spent most of their time studying the material, but also used self-testing to help them learn. The third group studied the material, and spent most of the time on self-testing. The three groups where then tested formally after 5 minutes. The group that only studied the content performed the best, and the group that performed worst was the group that spent most of the time self-testing. But look what happens when the formal test takes place a week later. The result is reversed; the group that spent most of the time studying performed the best. Clearly self-testing has leads to better storage strength.
Using testing for spaced practice does have its caveats and not everyone agrees on its efficacy. Most research on the topic has focused on simple knowledge (basic facts, vocabulary, rote learning). Van Gorg and Sweller (2015) stated that "the testing effect decreases as the complexity of learning material increases". What they meant by complex material referred to knowledge that showed interaction between various basic elements.
The point is is that testing is effective but we need to ensure that we are not just posing questions that require recall. We need to ask questions that require higher order thinking. Also we need to have a balance because we have a finite amount of time to deliver our curriculum and the more time we spend testing the less time we have for teaching the content and dealing with misconceptions. And actually if children fundamentally do not understand the content, no amount of testing is going to help. Below is a list of ideas that can help with space practice, some of these will be the focus of a future post:
- Diagnostic questions (including Quantum, Kahoot, Socrative, Plicekrs)
- Knowledge organisers and self-testing
- Delayed (interleaved) homework
- Cumulative knowledge tests
- Flash Cards
Block curriculum model
Spiral curriculum model
In my subject computer science one of the elements of the KS3 national curriculum requires pupils to understand simple Boolean logic. Throughout years 7-9 pupils will come across this several times in the following topics:
- Web searching (Year 7)
- Scratch (Year 7)
- Databases and SQL (Year 8)
- Spreadsheets (Year 8)
- Python (Year 9)
- Logic Circuits (Year 9)
I am going to leave you with a few basic principals which I hope the reader will take away:
- Any spaced retrieval practice is better than no spaced retrieval practice
- Testing is better than studying
- A spiral curriculum is better that a block curriculum
References
- Kirschner et al 2006
- Wallingham, Why don't students like school
- Bjork, R On the symbiosis of learning, remembering, and forgetting.
- Cepeda et al
- Roediger et al
- Ebbinghaus 1885
- Van Gorg and Sweller (2015)
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