memories are made of this

Education theory appears to be dominated by polarised debates. I’ve just come across another; minimal guidance vs direct instruction. Harry Webb has helpfully brought together what he calls the Kirschner, Sweller & Clark cycle of papers that seem to encapsulate it. The cycle consists of papers by these authors and responses to them, mostly published in Educational Psychologist during 2006-7.

Kirschner, Sweller & Clark are opposed to minimal guidance approaches in education and base their case on the structure of human cognitive architecture. As they rightly observe “Any instructional procedure that ignores the structures that constitute human cognitive architecture is not likely to be effective” (p.76). I agree completely, so let’s have a look at the structures of human cognitive architecture they’re referring to.

Older models

Kirschner, Sweller & Clark claim that “Most modern treatments of human cognitive architecture use the Atkinson and Shiffrin (1968) sensory memory–working memory–long-term memory model as their base” (p.76).

That depends on how you define ‘using a model as a base’. Atkinson and Shiffrin’s model is 45 years old. 45 years is a long time in the fast-developing field of brain research, so claiming that modern treatments use it as their base is a bit like claiming that modern treatments of blood circulation are based on William Harvey’s work (1628) or that modern biological classification is based on Carl Linnaeus’ system (1735). It would be true to say that modern treatments are derived from those models, but our understanding of circulation and biological classification has changed significantly since then, so the early models are almost invariably referred to only in an historical context. A modern treatment of cognitive architecture might mention Atkinson & Shiffrin if describing the history of memory research, but I couldn’t see why anyone would use it as a base for an educational theory – because the reality has turned out to be a lot more complicated than Atkinson and Shiffrin could have known at the time.

Atkinson and Shiffrin’s model was influential because it provided a coherent account of some apparently contradictory research findings about the characteristics of human memory. It was also based on the idea that features of information processing systems could be universally applied; that computers worked according to the same principles as did the nervous systems of sea slugs or the human brain. That idea wasn’t wrong, but the features of information processing systems have turned out to be a bit more complex than was first imagined.

The ups and downs of analogies

Theoretical models are rather like analogies; they are useful in explaining a concept that might otherwise be difficult for people to grasp. Atkinson and Shiffrin’s model essentially made the point that human memory wasn’t a single thing that behaved in puzzlingly different ways in different circumstances, but that it could have three components, each of which behaved consistently but differently.

But there’s a downside to analogies (and theoretical models); sometimes people forget that analogies are for illustrative purposes only, and that models show what hypotheses need to be tested. So they remember the analogy/model and forget what it’s illustrating, or they assume the analogy/model is an exact parallel of the reality, or, as I think has happened in this case, the analogy/model takes on a life of its own.

You can read most of Atkinson & Shiffrin’s chapter about their model here. There’s a diagram on p. 113. Atkinson and Shiffrin’s model is depicted as consisting of three boxes. One box is the ‘sensory register’ – sensory memory that persists for a very short time and then fades away. The second box is a short-term store with a very limited capacity (5-9 bits of information) that can retain that information for a few seconds. The third box is a long-term store, where information is retained indefinitely. The short-term and long-term stores are connected to each other and information can be transferred between them in both directions. The model based on what was known in 1968 about how memory behaved, but Atkinson and Shiffrin are quite explicit that there was a lot that wasn’t known.

Memories are made of this

Anyone looking at Atkinson & Shiffrin’s model for the first time could be forgiven for thinking that the long-term memory ‘store’ is like a library where memories are kept. That was certainly how many people thought about memory at the time. One of the problems with that way of thinking about memory is that the capacity required to store all the memories that people clearly do store, would exceed the number of cells in the brain and that accessing the memories by systematically searching through them would take a very long time – which it often doesn’t.

This puzzle was solved by the gradual realisation that the brain didn’t store individual memories in one place as if they were photographs in a huge album, but that ‘memories’ were activated via a vast network of interconnected neurons. A particular stimulus would activate a particular part of the neural network and that activation is the ‘memory’.

For example, if I see an apple, the pattern of light falling on my retina will trigger a chain of electrical impulses that activates all the neurons that have previously been activated in response to my seeing an apple. Or hearing about or reading about or eating apples. I will recall other apples I’ve seen, how they smell and taste, recipes that use apples, what the word ‘apple’ sounds like, how it’s spelled and written, ‘apple’ in other languages etc. That’s why memories can (usually) be retrieved so quickly. You don’t have to search through all memories to find the one you want. As Antonio Damasio puts it;

Images are not stored as facsimile pictures of things, or events or words, or sentences…In brief, there seem to be no permanently held pictures of anything, even miniaturized, no microfiches or microfilms, no hard copies… as the British psychologist Frederic Bartlett noted several decades ago, when he first proposed that memory is essentially reconstructive.” (p.100)

But Atkinson and Shiffrin don’t appear to have thought of memory in this way when they developed their model. Their references to ‘store’ and ‘search’ suggest they saw memory as more of a library than a network. That’s also how Kirschner, Sweller & Clark seem to view it. Although they say “our understanding of the role of long-term memory in human cognition has altered dramatically over the last few decades” (p.76), they repeatedly refer to long-term memory as a ‘store’ ‘containing huge amounts of information’. I think that description is misleading. Long-term memory is a property of neural networks – if any information is ‘stored’ it’s stored in the pattern and strength of the connections between neurons.

This is especially noticeable in the article the authors published in 2012 in American Educator from which it’s difficult not to draw the conclusion that long term memory is a store that contains many thousands of schemas, rather than a highly flexible network of connections that can be linked in an almost infinite number of ways.

Where did I put my memory?

In the first paper I mentioned, Kirschner, Sweller & Clark also refer to long-term memory and working memory as ‘structures’. Although they could mean ‘configurations’, the use of ‘structures’ does give the impression that there’s a bit of the brain dedicated to storing information long-term and another where it’s just passing through. Although some parts of the brain do have dedicated functions, those localities should be thought of as localities within a network of neurons. Information isn’t stored in particular locations in the brain, it’s distributed across it, although particular connections are located in particular places in the brain.

Theories having a life of their own

Atkinson and Shiffrin’s model isn’t exactly wrong; human memory does encompass short-lived sensory traces, short-term buffering and information that’s retained indefinitely. But implicit in their model are some assumptions about the way memory functions that have been superseded by later research.

At first I couldn’t figure out why anyone would base an educational theory on an out-dated conceptual model. Then it occurred to me that that’s exactly what’s happened in respect of theories about child development and autism. In both cases, someone has come up with a theory based on Freud’s ideas about children. Freud’s ideas in turn were based on his understanding of genetics and how the brain worked. Freud died in 1939, over a decade before the structure of DNA was discovered, and two decades before we began to get a detailed understanding of how brains process information. But what happened to the theories of child development and autism based on Freud’s understanding of genetics and brain function, is that they developed an independent existence and carried on regardless, instead of constantly being revised in the light of new understandings of genetics and brain function. Theories dominating autism research are finally being presented with a serious challenge from geneticists, but child development theories still have some way to go. Freud did a superb job with the knowledge available to him, but that doesn’t mean it’s a good idea to base a theory on his ideas as if new understandings of genetics and brain function haven’t happened.

Again I completely agree with Kirschner, Sweller & Clark that “any instructional procedure that ignores the structures that constitute human cognitive architecture is not likely to be effective”, but basing an educational theory on one aspect of human cognitive architecture – memory – and on an outdated concept of memory at that, is likely to be counterproductive.

A Twitter discussion of the Kirschner, Sweller & Clark model centred around the role of working memory, which is what I plan to tackle in my next post.

References

Atkinson, R, & Shiffrin, R (1968). Human memory: A proposed system and its control processes. In K. Spence & J. Spence (Eds.), The psychology of learning and motivation (Vol. 2, pp. 89–195). New York: Academic Press
Clark, RE, Kirschner, PA & Sweller, J (2012). Putting students on the path to learning: The case for fully guided instruction, American Educator, Spring.
Damasio, A (1994). Descartes’ Error, Vintage Books.
Kirschner, PA, Sweller, J & Clark, RE (2006). Why Minimal Guidance During Instruction Does Not Work: An Analysis of the Failure of Constructivist, Discovery, Problem-Based, Experiential, and Inquiry-Based Teaching Educational Psychologist, 41, 75-86.

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