Maps are a brilliant way of communicating information.
For me, maps work on two levels. The first is that they provide a visual representation of a landmass — or figurative landmass, like the organisation of a company, the brain, or the Dewey Decimal System — some structure with which we are largely unfamiliar and need to be better acquainted. The world gets smaller when you can map it and contain it within a single image: by delineating the boundaries, you are effectively constraining what lies in the Here Be Dragons quadrant of known unknowns. Having a map of the terrain is useful for developing confidence: just as you wouldn’t tackle a mountain without having checked out the map first, students find it reassuring when they know what you are going to cover in a lecture, even if they don’t yet have a handle on the details.
The second reason maps are useful is to provide a familiar structure for new information. The most obvious recent example of this is Mark Newman’s fantastic 2008 electoral maps of the US, in which this
though by that point it almost starts looking like something out of Babylon 5.
Because — it is assumed — we are sufficiently familiar with the underlying structure, we are free to explore the new data: how did a given state, county or timezone vote? What could potentially be a really complex information set if just dumped on us wholesale (for example, in the form of statistics) now becomes easily graspable, because it’s framed by a known structure.
We could do this more in teaching: provide an early, basic road-map to students about the borders of the area under discussion, and progressively revisit and colour in the missing pieces. This is not always how we do things: a popular pedagogic M.O. seems to be to introduce Topic A and then fill in all the details before moving on to Topic B, etc. — but what we could do is show a map of Topics A through H first, and then revisit each topic once students have understood where the edges of the map are.
Good teaching practice means being more explicit about maps.