Once, long ago, I encountered a discussion on different ways of computing – I cannot remember who wrote the article or when/where it was. Two images have stayed in my mind.

If you have a lot of broken spaghetti and you want to find the longest piece, you could do three things. One, you could measure each piece with a ruler, number each piece and tabulate the lengths as you go. After this you would scan the values you recorded for the largest value, note its number and retrieve the piece. Two, you could pick up a piece and compare it to another piece, discard the shortest and continue comparing to another piece. When all pieces but the one you are currently holding are in the discard pile, you have the longest piece. Or three, you could gather up the whole lot of spaghetti in your hands and hold them in an upright bundle. You would then tap the bundle lightly on the table so that all the pieces rested on the table. The longest piece would stand out as the tallest and could be picked out easily. Method three is very fast and easy when compared to the others. It is like an analog calculation rather than a digital one.

The other example I remember was finding the centre of three points – the point which is equal distant from all three points or the centre of the circle that passes through all three points. It is possible to construct, with compass and straight edge, the line that is equally distant between each pair of points. There will be a point where the three lines cross and that is the point you want. Another way is to attach an identical spring to each point and then bring the other ends of the three springs together and attach them all to the same little vertical stake. Where the stake rests is the centre point as the three springs will be identically extended. Unless you have to go out and buy the springs etc. but do not have to buy a compass, the spring method is instantaneous. Again it is like the different between an analog calculation and a digital one.

When we think of the brain as a computer, we have to be careful about what type of computer we have in mind, as well as remembering that this is just a rough metaphor.