Short-term Long-term Memory

I’ll begin looking at the structure of memory by looking at short-term memory, long-term memory, and how information is moved from one to the other (short-term to long-term = encoding, long-term to short-term = retrieval).

Short-term memory is exactly what the name implies, memory for the short term. It is the memory you are using to feed your thinking. The number of items you can hold in short-term memory is between about four and eight (5±2 or 7±2 depending on the research). You keep items active in short-term memory by rehearsing them in your head. You know what this feels like when you get a phone number. As long as you can keep repeating it in your mind, you don’t forget. As soon as another item comes along, you begin to lose part of the number. You can chunk information together and make it one item, so (keeping with the phone number analogy) a familiar area code can be treated as a chunk, even though it is three numbers long.

In learning, short-term memory is the memory that you are working with. It defines what you have in your mind at any given moment. You take what you have in your short term or working memory, and look for meaningful links to what you already have in your long-term memory. By establishing meaningful, semantic links and associations with the information you already have in long-term memory, you can move your new information from short-term memory to a more permanent store – long-term memory.

Long-term memory is a durable, permanent store that is organised semantically (by meaning). There are three aspects to long-term memory: encoding (getting it in there), storage (keeping it there), and retrieval (getting it back out). Formal learning is primarily concerned with encoding and retrieval. However, a lack of understanding about how long term memories are encoded, organised and stored means that there are powerful learning opportunities lost.

In education, the ways we are taught to encode long-term memories is based on our subjective experience with short-term memory – as long as we rehearse our short-term memories, we can keep them alive. As a result, the naive thinking is that we need to rehearse what we have in our short-term memories over and over in order to transfer that information to long-term memory. That’s not how it works, but that’s how we’re taught. Going over how long-term memory is organised can help us understand how long-term memories are encoded.

Because long-term memory is organised as a semantic network, the information that is transferred to long-term memory is organised according to how related the information is. A caveat here is necessary. The relatedness of information is completely subjective in that individuals decide what and how information is related. It would be nice to think that my long-term memory organisation is truly representative of reality (and I think that it is), however, my reality isn’t exactly the same as your reality.

The information that is moved to long-term memory is encoded through links to information that we already know, hence the semantic organisation. This is important for a couple of reasons. Firstly, because information is attached to other information, the more information you have encoded and stored already, the more links you have to encode other information. This is fantastic, because it means the storage capacity of long-term memory is essentially unlimited. The more you know, the more you can learn.

The other reason knowing semantic organisation is the way long-term memory works is that as information is added to our long-term store, the information that is there is changed. Our understanding of what we already knew is altered, and (usually) our understanding is deepened.

In education, I kept hearing that overassessment is a bad thing. I was told that overassessment is a bad thing. Overassessment is assessing something more than once. Once you have measured how well a student has learned something, to ask for the same measurement again is poor practise. You already know what your student has learned, so you shouldn’t assess it again. However, given what we know about how memory is organised, and since we know that when new information is added, it changes the old information as well, why wouldn’t we want overassessment? Asking the same question more than once (if it is a good question) will allow a learner to demonstrate how their understanding of something has developed as they have engaged in their learning opportunities. What a lost opportunity, due to a lack of understanding of how memory works.

Another problem with formal education and the lack of understanding of how long-term memory works, has to do with retrieval of information.

I remember how fascinating I was when I learned about something called state dependent learning. I first heard of it as a second year undergraduate in a Cognitive Psychology class. State dependent learning is the principle that you will remember much better if your state of recall is closely matched to your state of encoding. A great illustrative example of how this works was a study where memory was tested in scuba gear at the bottom of a pool. When the divers learned something at the bottom of the university swimming pool, they could recall it much easier if they were tested on the information at the bottom of the pool than if they were tested on the information in a classroom sitting at desks. If you try to recall information in a state (situation, place, mood etc.) that is as close to the state you were in when you learned the information, your recall will be much better. The take home message (at least for me as a student at the time) is that you need to study for your exams in a state as close to the state that you will be taking the exams as possible. Doing this will maximise your performance and give you the highest grade.

If you actually want to learn something that you might need to access in a different situation sometime in the future, this is the worst possible strategy. You are keeping the information you are learning linked to a single state (in order to maximise exam performance) and are not making links to other times, places and situations where the information might prove useful – the problem of transference of knowledge.

Since learning in formal education should be about preparing a person for what they need to know in the future, learning should be about accumulating knowledge that will aid in critical analysis, problem solving, and decision making (all of which need a solid content base from which to work). It is doubtful that many critical decisions, or rational problems are going to be solved in rooms that resemble exam halls.

State dependent learning might improve recall from long-term memory in a specific situation, but it does nothing to build an appropriate content base that a learner can draw on in the future to successfully engage in what the world needs the most of – thinking.

A far better strategy (for learning) is to engage in recall in as many different states as possible. Knowing how to solve problems involving fractions on paper while sitting at a desk is not a useful skill to have. Being able to apply knowledge about fractions in a kitchen or on a building site, or any other situation that could use the knowledge, is what is really useful. Unfortunately, this isn’t what is usually done in education, and overassessment being bad (as a principle) means that it is unlikely to be changed in the near future.


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