The Point

Sunday, May 25, 2008

Emergent behaviour






















Fractal origami

You know when you get a word that just sort of sticks in your head and you can't figure out where it came from or what it means? I had this the other day with the word 'tesseract.' I could not figure out why it had wormed its way into my brain or what it meant, but my friend Adam and I speculated that it probably had something to do with tessellation, the kind of repeating of part of an object over and over to make a pattern.

When I got home I wikipediaed the word and got even more confused. The way it explained it is this: if you have a line and you want to make it into a square, you move out at perpendicular angles from it until you make a closed object. Right angles. And if you want to make a cube, you move out at perpendicular angles from the vertices of the square until you make another closed object, which is now in three dimensions. Okay, so apparently a tesseract is what you get if you make the same movement out from a cube. It can look like a cube inside a cube... or sometimes not. Confused? So was I. But it got me thinking about this very basic idea that extraordinarily (and sometimes mystifyingly) complex things can arise from the extension of very simple principles in a system.

Which is kind of the basic idea between a field of science I've been sort of captivated at a distance by for years: emergence. Emergence is the study of the complex behaviours of systems arising from the simple, sometimes even stupid behaviours of individuals making up the system as a whole. A good example is the way a colony of ants behave.

On their own, ants can be pretty dumb. Out foraging for food (and I've never studied ants, but this is my understanding of this thing), ants put their little antennae up to smell for anything of interest, but they're just kind of running around every which way, back and forth, in a way that looks pretty random to an observer. And then, it turns out, when they run into something good, they lay down a pheromone trail that lets other ants know which way to go to find it.

And when a a second ant bumps into this pheromone trail, catches that tasty tasty scent and follows it, it lays down its own chemical trail, amplifying the effect for the next ant and the next ant and the next ant. Before you know it, these little hiking trails become big ant super highways. This is the kind of thing I've heard described as 'architecture through error.' It's not planned, it's not coordinated by some director, and if you looked at each individual ant to try to extrapolate some picture of what this pheromone gland might be used for, a food superhighway wouldn't necessarily be intuitively obvious. But it works.

This is the same kind of thing that's going on in your brain. You can't look at a neuron and see a memory. Just holding up one cell, it'd be impossible to find where love is located, or a fear of sea urchins. But when you get an eight and a half pound ball of neurons all firing together, you get emergent properties that are pretty incredible. Emergent behaviour is behind the exponentially more accurate guesses a crowd makes the more people there are guessing, behind the surprising accuracy of articles written by thousands of amateurs on Wikipedia... it's everywhere.

If you want to learn more about it, I recommend:
  1. This episode about emergence from Radiolab, a show out of WNYC in New York. It's brilliant. You'll get a kick out of it, and who wouldn't love a co-host with a name like Jad Abumrad?
  2. This website called Exploring Emergence, where you can play around with little games that show how simple rules like 'pixel on,' 'pixel off' can make some craaazy crazy things.
The picture of the crazy origami above is a Creative Commons licensed photo from a user named polyscene. Don't you just love CC? Incidentally, I'm still trying to find a biologist who can explain to me the connection between emergent behaviour and entropy. Just putting it out there. Thanks.

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posted by Christopher at 10:21 p.m.

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