Theory of Memory
Much has been written about how we think memory works. I’ll just give some of the headlines and describe the bits that have most impact on teaching and learning.
First a simplified view of what is called working memory derived from the model presented by Baddeley & Hitch, 1974. The model describes a mechanism rather that particular places in the brain. You could not, for example, identify a lump of the brain which was working memory.
Sensory Memory Central Executive Long term memory
Phonological loop Episodic Buffer Visuospatial Sketchpad
The central executive is the name given to the process in the brain that manages the activity of inspecting the sensory information that comes into the working memory. One function of the central executive is to pay attention to sensory inputs.
Working memory is where stuff we detect via our senses gets initially processed. In the phonological loop the inputs loop around, gradually decaying over a matter of seconds. A similar process happens in the visuospatial sketchpad.
A critical issue for teachers about working memory is that it is a very short term. Think of a telephone number you have just been told and need to remember. To keep it in working memory while we look for somewhere to write it down we have to keep saying the number to ourselves. To keep it looping.
Working memory has a small capacity. Cognitive scientists now believe it can retain around 4 items. The size of these items depends on whether we know them already, ie they are in long term memory, or if they are new.
Working memory function, with its limited capacity and short term loop, is also where we engage in the process called thinking which uses some of the already limited capacity. The processing of what we think about takes up working memory.
Working memory is soon overwritten by other information, we pay attention to, coming from our senses. Then what was there is probably lost. This has an impact on the effect of distractions while learning.
If the central executive decides that the information currently in working memory is worth paying attention, and it does this by checking with material already stored in long term memory, then this information gets encoded (in some way in patterns of neurons, cells in the brain) and stored.
Cognitive load relates to the amount of information working memory can deal with. Cognitive overload means we are bombarding working memory with more than it can cope with. In general, teachers should be doing what they can to avoid cognitive overload in their learners and in themselves while teaching.
Long term memory is exactly that. The place(s) where memories that we keep get stored.
But the memory stored in long term memory is not automatically accessible. We can only recall memories if the central executive can access them somehow. This, in teaching, is where methods to strengthen recall come in.
As far as we know there is no limit to the amount that long term memory can hold. When working memory recalls from long term memory the chunks can be quite large. Some elements in long term memory are not chunked and take up more working memory when recalled. We can manipulate large amounts of ‘knowledge’ in working memory if it comes from the store in long term memory.