deep structure and understanding
Extracting information from data is crucially important for learning; if we can’t spot patterns that enable us to identify changes and make connections and predictions, no amount of data will enable us to learn anything. Similarly, spotting patterns within and between facts enables us to identify changes and connections and make predictions will help us understand how the world works. Understanding is a concept that crops up a lot in information theory and education. Several of the proposed hierarchies of knowledge have included the concept of understanding – almost invariably at or above the knowledge level of the DIKW pyramid. Understanding is often equated with what’s referred to as the deep structure of knowledge. In this post I want to look at deep structure in two contexts; when it involves a small number of facts, and when it involves a very large number, as in an entire knowledge domain.
When I discussed the DIKW pyramid, I referred to information being extracted from a ‘lower’ level of abstraction to form a ‘higher’ one. Now I’m talking about ‘deep’ structure. What’s the difference, if any? The concept of deep structure comes from the field of linguistics. The idea is that you can say the same thing in different ways; the surface features of what you say might be different, but the deep structure of the statements could still be the same. So the sentences ‘the cat is on the mat’ and ‘the mat is under the cat’ have different surface features but the same deep structure. Similarly, ‘the dog is on the box’ and ‘the box is under the dog’ share the same deep structure. From an information-processing perspective the sentences about the dog and the cat share the same underlying schema.
In the DIKW knowledge hierarchy, extracted information is at a ‘higher’ level, not a ‘deeper’ one. The two different terminologies are used because the concepts of ‘higher’ level extraction of information and ‘deep’ structure have different origins, but essentially they are the same thing. All you need to remember is that in terms of information-processing ‘high’ and ‘deep’ both refer to the same vertical dimension – which term you use depends on your perspective. Higher-level abstractions, deep structure and schemata refer broadly to the same thing.
deep structure and small numbers of facts
Daniel Willingham devotes an entire chapter of his book Why don’t students like school? to the deep structure of knowledge when addressing students’ difficulty in understanding abstract ideas. Willingham describes mathematical problems presented in verbal form that have different surface features but the same deep structure – in his opening example they involve the calculation of the area of a table top and of a soccer pitch (Willingham, p.87). What he is referring to is clearly the concept of a schema, though he doesn’t call it that.
Willingham recognises that students often struggle with deep structure concepts and recommends providing them with many examples and using analogies they’re are familiar with. These strategies would certainly help, but as we’ve seen previously, because the surface features of facts aren’t consistent in terms of sensory data, students’ brains are not going to spot patterns automatically and pre-consciously in the way they do with consistent low-level data and information. To the human brain, a cat on a mat is not the same as a dog on a box. And a couple trying to figure out whether a dining table would be big enough involves very different sensory data to that involved in a groundsman working out how much turf will be needed for a new football pitch.
Willingham’s problems involve several levels of abstraction. Note that the levels of abstraction only provide an overall framework, they’re not set in stone; I’ve had to split the information level into two to illustrate how information needs to be extracted at several successive levels before students can even begin to calculate the area of the table or the football pitch. The levels of abstraction are;
• data – the squiggles that make up letters and the sounds that make up speech
• first-order information – letters and words (chunked)
• second-order information – what the couple is trying to do and what the groundsman is trying to do (not chunked)
• knowledge – the deep structure/schema underlying each problem.
To anyone familiar with calculating area, the problems are simple ones; to anyone unfamiliar with the schema involved, they impose a high cognitive load because the brain is trying to juggle information about couples, tables, groundsmen and football pitches and can’t see the forest for the trees. Most brains would require quite a few examples before they had enough information to be able to spot the two patterns, so it’s not surprising that students who haven’t had much practical experience of buying tables, fitting carpets, painting walls or laying turf take a while to cotton on.
visual vs verbal representations
What might help students further is making explicit the deep structure of groups of facts with the help of visual representations. Visual representations have one huge advantage over verbal representations. Verbal representations, by definition, are processed sequentially – you can only say, hear or read one word at a time. Most people can process verbal information at the same rate at which they hear it or read it, so most students will be able to follow what a teacher is saying or what they are reading, even if it takes a while to figure out what the teacher or the book are getting at. However, if you can’t process verbal information quickly enough, can’t recall earlier sentences whilst processing the current one, miss a word, or don’t understand a crucial word or concept, it will be impossible to make sense of the whole thing. In visual representations, you can see all the key units of information at a glance, most of the information can be processed in parallel and the underlying schema is more obvious.
The concept of calculating area lends itself very well to visual representation; it is a geometry problem after all. Getting the students to draw a diagram of each problem would not only focus their attention on the deep structure rather than its surface features, it would also demonstrate clearly that problems with different surface features can have the same underlying deep structure.
It might not be so easy to make visual representations of the deep structure of other groups of facts, but it’s an approach worth trying because it makes explicit the deep structure of the relationship between the facts. In Seven Myths about Education, one of Daisy’s examples of a fact is the date of the battle of Waterloo. Battles are an excellent example of deep structure/schemata in action. There is a large but limited number of ways two opposing forces can position themselves in battle, whoever they are and whenever and wherever they are fighting, which is why ancient battles are studied by modern military strategists. The configurations of forces and what subsequent configurations are available to them are very similar to the configurations of pieces and next possible moves in chess. Of course chess began as a game of military strategy – as a visual representation of the deep structure of battles.
Deep structure/underlying schemata are a key factor in other domains too. Different atoms and different molecules can share the same deep structure in their bonding and reactions and chemists have developed formal notations for representing that visually; the deep structure of anatomy and physiology can be the same for many different animals – biologists rely heavily on diagrams to convey deep structure information. Historical events and the plots of plays can follow similar patterns even if the events occurred or the plays were written thousands of years apart. I don’t know how often history or English teachers use visual representations to illustrate the deep structure of concepts or groups of facts, but it might help students’ understanding.
deep structure of knowledge domains
It’s not just single facts or small groups of facts that have a deep structure or underlying schema. Entire knowledge domains have a deep structure too, although not necessarily in the form of a single schema; many connected schemata might be involved. How they are connected will depend on how experts arrange their knowledge or how much is known about a particular field.
Making students aware of the overall structure of a knowledge domain – especially if that’s via a visual representation so they can see the whole thing at once – could go a long way to improving their understanding of whatever they happen to be studying at any given time. It’s like the difference between Google Street View and Google Maps. Google Street View is invaluable if you’re going somewhere you’ve never been before and you want to see what it looks like. But Google Maps tells you where you are in relation to where you want to be – essential if you want to know how to get there. Having a mental map of an entire knowledge domain shows you how a particular fact or group of facts fits in to the big picture, and also tells you how much or how little you know.
Daisy’s model of cognition
Daisy doesn’t go into detail about deep structure or schemata. She touches on these concepts only a few times; once in reference to forming a chronological schema of historical events, then when referring to Joe Kirby’s double-helix metaphor for knowledge and skills and again when discussing curriculum design.
I don’t know if Daisy emphasises facts but downplays deep structure and schemata to highlight the point that the educational orthodoxy does essentially the opposite, or whether she doesn’t appreciate the importance of deep structure and schemata compared to surface features. I suspect it’s the latter. Daisy doesn’t provide any evidence to support her suggestion that simply memorising facts reduces cognitive load when she says;
“So when we commit facts to long-term memory, they actually become part of our thinking apparatus and have the ability to expand one of the biggest limitations of human cognition”(p.20).
The examples she refers to immediately prior to this assertion are multiplication facts that meet the criteria for chunking – they are simple and highly consistent and if they are chunked they’d be treated as one item by working memory. Whether facts like the dates of historical events meet the criteria for chunking or whether they occupy less space in working memory when memorised is debatable.
What’s more likely is that if more complex and less consistent facts are committed to memory, they are accessed more quickly and reliably than those that haven’t been memorised. Research evidence suggests that neural connections that are activated frequently become stronger and are accessed faster. Because information is carried in networks of neural connections, the more frequently we access facts or groups of facts, the faster and more reliably we will be able to access them. That’s a good thing. It doesn’t follow that those facts will occupy less space in working memory.
It certainly isn’t the case that simply committing to memory hundreds or thousands of facts will enable students to form a schema, or if they do, that it will be the schema their teacher would like them to form. Teachers might need to be explicit about the schemata that link facts. Since hundreds or thousands of facts tend to be linked by several different schemata – you can arrange the same facts in different ways – being explicit about the different ways they can be linked might be crucial to students’ understanding.
Essentially, deep structure schemata play an important role in three ways;
Students’ pre-existing schemata will affect their understanding of new information – they will interpret it in the light of the way they currently organise their knowledge. Teachers need to know about common misunderstandings as well as what they want students to understand.
Secondly, being able to identify the schema underlying one fact or small group of facts is the starting point for spotting similarities and differences between several groups of facts.
Thirdly, having a bird’s-eye view of the schemata involved in an entire knowledge domain increases students’ chances of understanding where a particular fact fits in to the grand scheme of things – and their awareness of what they don’t know.
Having a bird’s-eye view of the curriculum can help too, because it can show how different subject areas are linked. Subject areas and the curriculum are the subjects of the next post.