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Exploring Emergence

The World of Langton's Ant:
Thinking about "Purpose"

Part 2
Looking Inside: How's It Work?

Langton's ant acts in what seem to be quite sophisticated ways. What do you imagine it takes to do that? Something comparably sophisticated? The answer turns out to be no. What's inside the ant is actually a remarkably simple set of instructions:

Go forward one square.

If you are on a light square, change it to dark, and turn right.

If you are on a dark square, change it to light, and turn left.

Repeat

That's it? Yes, that's it. The aimless wandering, the transition to road building, and the persistant road building despite barriers all result from nothing more than those two instructions in the ant and a world for the ant to interact with that consists of squares that can be either dark or light.

One Step At A Time

You probably don't, and certainly shouldn't, take us at our word on this. Click on Set/Reset and then click the new "Go Once" button to the right. This way you can watch individual steps that the ant is taking and be sure what we've said is true. On the first step (the ant starts on a light square), the ant goes forward one, finds itself on a light square and turns it dark, and turns right. You can't see the light square yet but you will after the next step, when the ant goes forward, finds itself again on a light square (and turns it dark) and turns right again. Keep following the ant step by step for a bit. How come the ant doesn't just keep turning to the right forever?

To be sure that ant ALWAYS follows the same rules, you can try lots of variations by changing individual square colors yourself using the "Create Barrier" and "Remove Barrier" buttons. What happens, for example, if the ant starts on a dark square instead of a light one?

So, now we've made some interesting observations, gotten to know the ant from the outside and the inside. Let's start thinking about what it means, what we can make from all that, what lessons it might have for other things.


"The World of Langton's Ant" was produced by Paul Grobstein with the Summer 2005 Serendip/SciSoc group. Applets were created with NetLogo by Rebekah Baglini, building on earlier work. Our thanks to the Emergent Systems Working Group for fertile conversations from which this emerged and to which we hope it further contributes.
Introduction
Watching
Looking Inside
Agents/Environments | Observers | Architects | Beyond Determinism?
Summary and ...
Further reflections on Emergence and Science Education
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