How Memory Works


Key Takeaways

  1. There are different types and they each matter. Short term, working, and long-term memory all need to be activated for students to learn.
  2. How students process information impacts the quality of their learning. Student process information into their memories using encoding, storage and retrieval.
  3. Forgetting helps students to learn. Provided they were paying attention in the first place!
  4. Space and interleaving can increase the chances of students remembering. Good teaching will space and interleave content to promote learning

If Dylan Wiliam contends that The main purpose curriculum is to build up the content of long-term memory’, then teachers need to know about memory. Into this space steps David Didau, a former teacher, whose excellent blog ‘The Learning Spy’ drew him to prominence in the UK, including working with both Ofsted and the Department of Education (UK). Didau’s book ‘What if everything you knew about education was wrong?’ questions the fundamental beliefs of the schooling system and asks the fundamental question: ‘how do kids remember what they have learnt?’


There are different types of memory and they each matter.


Short-term  memory

At every moment in a lesson, you and your students are being bombarded with thousands of pieces of information from the classroom environment. Things like the room temperature, what Sam is saying and thinking ‘my left foot is a bit itchy‘ can all occupy our thoughts in a given moment. What we pay attention to is key when it comes to memory. Information enters the short-term memory when attention is paid to that piece of information. For instance, the firmness of the chair on which a student is sitting is being relayed to their brain at all points in a lesson but it is only when they focus that stimuli that it enters the short term memory. This means that if a student does not pay attention to what you want them to learn, they will not learn it.

The capacity and duration of short-term memory are limited. Revilin contends that without rehearsing or repeating information, the duration of short-term is approximately 18 seconds. While Miller’s magic number paper suggests that short term memory has a capacity of seven items plus or minus two. More recent research suggests this number could be even lower.


Working memory

Working memory is the small amount of information that can be held in mind and used in the execution of cognitive tasks. According to Didau “Working memory is synonymous with awareness” in that it allows us to engage with the information in our short-term memory, manipulate it and if required, connect it to information from our long-term memory.

From What if everything you knew about education was wrong?

“We can store some immediate experiences and a little bit of knowledge, but working memory also allows us to reach back into our long-term memory and pull bits into the foreground as needed. We can then process this mix of what we’re experiencing and what we previously knew to make decisions and achieve our goals.”



Long-term memory

In contrast to short-term memory, long-term memory has an infinite capacity. Effectively if you can recall anything that has not happened in the last 20 seconds then it has been stored in your long-term memory (the exception is if you have been repeating that something to over and over – this has just kept it in your short-term memory).

Effectively, to be stored in long-term memory, an idea of thought must enter the short-term memory, be manipulated by the working memory and then usually, connected with prior knowledge or developed into a new schema. For instance right now, we hope, you’re manipulating what you’re reading right now and adding to your schema of memory and learning. Long-term memory can be broken down into further categories: explicit (knowledge of events/times/facts/events and experiences) and implicit memory (procedural memory such as how to ride a bike and emotional memories).

What is highly relevant to the classroom is that the way students encode, process, and retrieve information is a significant factor in whether they will remember the information you have exposed them to during your lessons.


How students process information impacts the quality of their learning

As we move to the process of memorising, let us be clear, our brain is not a computer or video recorder. Sometimes what we remember misses a simple and obvious piece of information from events. Occasionally, we even recall details that were not actually in the original event. Because memories are constructed through our individual thoughts and feelings, it is easy for two people to witness the same event but have vastly differing stories – just ask any year level coordinator! So, the process of memorising something is a very personal affair – which increases the difficulty of our teaching job. However, the process of remembering information is the same for all students – encoding, storage and retrieval.


Encoding

“Encoding is getting the information in”. For this to happen, a student needs to pay attention to a stimulus. This attention places the stimulus into their short-term memory. Then for the information to be encoded, the student needs to link this information to prior knowledge. If the information is not encoded or linked by the working memory, it will not transfer to long-term memory. One way to think about encoding is that it is the way a student files information. Some students will encode information with the efficiency of a librarian, and others may have a more unique filing system. knowledge can be encoded in several forms, including

  • Visual encoding (think pictures/images)
  • Acoustic encoding (sound)
  • Semantic encoding (language and meaning)

Note: Encoding has been found to be more effective if the information is encoded in more than one way, e.g. visually and semantically.  


Storage

Memory and knowledge can be stored in the sensory memory (for a few seconds at most), the short term memory (for certainly less than 30 seconds) and the long-term memory (indefinitely). The process of storing memories is the same for all cognitively normative students but each student is unique in terms of how that information has been encoded due to their individual interests and experiences.  

From What if everything you knew about education was wrong?

The term ‘storage strength’ is a measure of how interconnected or entrenched information is, how related it is to everything else that’s in our memories.



Retrieval

What every teacher wants their student to be able to do is find taught information again at the time it’s needed. Unfortunately, this is easier said than done. Retrieval strength is how quickly and easily a person can locate a piece of information or schema in their long-term memory. This strength will differ regarding different ideas and areas of knowledge. 


Forgetting helps students to learn.

This seems counter-intuitive, doesn’t it? If we want them to learn something, why would we want them to forget it? Surely forgetting is the enemy of learning.

Not so. First, let’s go back to some old research. Harmann Ebbinghaus broke ground in the importance of forgetting in 1885. The forgetting curve (below) is a lasting testament to his research.

Effectively, what Ebbinghaus discovered is that when we learn something, if we do not review it over time, we become less likely to remember it. However, after we have ‘forgotten’ something, it is quicker to relearn and it is also more likely that this information will be retained in the future. This has significant implications for the teaching and learning practices that enable students to encode, store and retrieve knowledge.

From What if everything you knew about education was wrong?

“Possibly counterintuitively, the higher the retrieval strength of an item of memory – that is, how easy it is for us to recall a piece of information right now – the smaller the gains in storage strength from additional study or practice. So, if something is highly accessible, virtually no learning can happen! No matter what you do, there will be no additional increases in storage strength from additional study or practice.


So, what does this all mean for our teaching? We need to make our classroom engaging and challenging enough that students are likely to pay attention to the curriculum being enacted in the classroom, but not so challenging that students are overwhelmed. We need to employ formative assessment to monitor if this is the case and if the student has retained the required content and adjust our teaching accordingly.  We should also carefully consider the sequence of our curriculum.


Space and interleaving can increase the chances of students remembering


Spacing

As the learning curve graph above suggests, the recalling of information increases its storage strength over time. When we space a student’s exposure to content, they are more likely to recall it in the long term. Didau draws on the work of Piotr Wozniak in in making this point.

From ‘What if everything you knew about education was wrong?’

It seems that by allowing ourselves to forget before further study, not only do we filter out competing information but we get more practice in trying to actively recall what we want to learn…


This may be because longer spaces allow for more forgetting, but also gives the learner the chance to find out weakness in memory and correct for them.

So a fair question at this point is how often should we ‘space’ content? There isn’t clear consensus on this but Barak Rosenshine’s work emphasises a daily, weekly, and monthly review and a good starting point for consideration. If you are preparing students for high stakes exams, Didau emphasises the work of Capeda et al. who developed these useful guidelines.

Time to testOptimum interval between study sessions
1 week1 to 2 days
1 month1 week
2 months2 weeks
6 months3 weeks
1 year4 weeks



Interleaving

But what do I teach when I am waiting for the student to forget what they have learnt? This is where the concept of interleaving come in.


As depicted above, most curriculum is blocked; that is, teachers design units with a singular focus, for example, the concept of ‘light’ in Physics. This unit may run for a number of weeks before moving to the next unit on ‘motion’. Students feel confident sequentially learning information. However, research would suggest that this confidence doesn’t translate into long term learning. Interleaving in topics that are readily switched between ‘feels’ harder to students but has better long term learning.  

From ‘What if everything you knew about education was wrong?’

Blocking leads to deceptively compelling short-term gains. It ’feels right’ to teach this way. But as we have seen, our instinct can be misleading…Maybe it’s studying in blocks provides the ‘illusion of knowing’ and gives us a false sense of security; we think we are getting better. In contrast, interleaving creates anxiety, the feeling that things are unpredictable and therefore we need to take more care.


There is also some debate about what counts as interleaved and spaced content. Is a ‘do now’ or ‘starter’ activity enough to interleave content, or does it has to be a complete lesson? The jury is still out on this one but increasing reflection and interleaving in some lessons is a good starting place,

Want to know more Craig Barton has an excellent podcast with the King and Queen of memory research, Robert and Elizabeth Bjork.

Key Takeaways

  1. There are different types and they each matter. Short term, working, and long-term memory all need to be activated for students to learn.
  2. How students process information impacts the quality of their learning. Student process information into their memories using encoding, storage and retrieval.
  3. Forgetting helps students to learn. Provided they were paying attention in the first place!
  4. Space and interleaving can increase the chances of students remembering. Good teaching will space and interleave content to promote learning