Late night thoughts #4

by reestheskin on 11/04/2019

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Late night thoughts on medical education #4: Maps and scheming over schemas

One of the problems in learning clinical medicine is the relation between an overall schema of what you have to learn and the detail of the various components that make up the schema. I can remember very early in my first clinical year, seeing a child with Crohn’s disease, and subsequently trying to read a little about this disorder. My difficulty was that much of what I read, contrasted Crohn’s with various other conditions — ulcerative colitis, Coeliac and so on. The problem was that I didn’t know much about these conditions either. Where was I too start? A wood and the trees, issue.

I have, pace Borges written about maps and learning before. This is my current riff on that theme. I am going to use learning how to find your way around Edinburgh as my example. There is a simple map here.

That fine city

The centre of Edinburgh is laid out west to east, with three key roads north of the railway station. You can imagine a simple line map — like a London underground map — with three parallel main roads: Prince’s street, George Street and Queen street. You can then add in a greater level of detail, and some arterial routes in and out of the city centre.

If you were visiting Edinburgh for the first time, you could use this simple schema to try and locate places of interest. If you were lost and asked for help, it night prove useful. You could of course remember this simple plan — which is the most northerly of these three streets and so on — or perhaps use a simple cognitive prosthesis such as a paper map.

Students learn lots of these maps when they study medicine, because they are asked to find their way around lots of cities. They also forget many of them. The more complete the map, the harder it is to recall. If they have to navigate the same terrain most days, their recall is better. No surprises there. If you challenge a student you can literally see them reproducing the ‘map tool’ as they try and answer your question. Just like if you ask them the causes of erythema nodosum, you can literally see them counting their list on their fingers.

Novices versus experts

There are obvious differences between novices and experts. Experts don’t know need to recall the maps for multiple cities, instead they reside in the city of their specialty. Experts also tend not be good at recalling long lists of the causes of erythema nodosum, rather they just seem to recall a few that are relevant in any particular context. The map mataphor provides clues to this process.

If you challenge experts they can redraw the simple line figure that I started this piece with. They can reproduce it, although as the area of coverage is increased I suspect their map may begin to break the rules of 2D geometry: they move through the city professionally, but they are not professional cartographers.

The reason for this failure is that experts do not see the ‘line map’ in the mind’s eye, but actually see the images of the real geography in their mind as they move through it. They can deduce the simple line graph, but this is not what they use diagnostically to find their way around. By contrast, they see the images of the roads and building and can navigate based on those images. They have their own simulation, that they can usually navigate without effort. Of course, when they first visited Edinburgh, they too probably crammed a simple line graph, but as they spent time in the city, this simple cognitive tool, was replaced by experience.

This sort of way of thinking was AFAIK first highlighted by the US philosophers Dreyfus and Dreyfus. They pointed out novices use ‘rule based’ formal structures, whereas experts did not. This is obvious in craft based perceptual subjects such as dermatology (or radiology or histopathology). Experts don’t use check list to diagnose basal cell carcinomas or melanoma, they just compare what they see with a personal library of exemplars. The cognitive basis for this ability, taking advantage of the idea of ‘familial likeness’, has been studied for a long time, although I do not think the problem is solved in any sort of formal way. It is usually very fast — too fast for the explicit scoring methods promoted by most clinicians and educators.

Although this way of thinking is easiest to appreciate in perceptual subjects such as dermatology, most clinicians do not view things this way — even when the experimental evidence is compelling. Some believe the explicit rules they use to teach students, are how they do it themselves. Others believe that experts are fluent in some high level reasoning that students to not possess . They like to think that their exams can test this higher level ‘deep’ reasoning. I think they may be mistaken.

Finding the takeaway

There are some ideas that follow from my story.

  1. Without wishing to open up the delusion that factual recall is not critical to expertise, experts and novices do not possess the same methodology for working out what is going on. This means that we might promote simple structures that are placeholders for expert knowledge that will come through experience. These placeholders are temporary and meant to be replaced. We should be very careful about making them play a central role in assessment. To me this is akin to the way that some written Asian languages have different systems for children and adults.
  2. Some of these placeholders might need to be learned, but some can be external cognitive prostheses, such as a paper map or a BNF.
  3. Having to memorise lots of simple line-maps for lots of different cities imposes a heavy cognitive load on students. Long term memorisation of meaningful concepts works best when you don’t know you are trying to memorise things, but rather, you were trying to understand things. Our students are all too often held hostage by getting on by ‘reproducing’ concepts rather than understanding things.
  4. Becoming expert means minimising the distance between rote learning of line-maps and building up your library of exemplars. Distance here refers to time. In other words, the purpose of prior learning is to give you the ability to try and navigate around the city so that you can start the ‘real’ learning. Some cities are safer than others — especially if you might get lost. Better to start in Edinburgh than Jo’burg (the ITU is not the place to be a novice).
  5. If you look at the process of moving from being a student to acquiring high professional domain expertise (as a registrar), it would seem better to focus on a limited number of cities. What we should not do is to expect students to be at home in lots of different places. Better to find you feet, and then when they get itchy, move on.