CHAIN 26
LENGTH 4 REPETITION 0.0 SCORE 0.0
diet 1 produce 1 bean 1 pea 1
SUGAR and spice motivated many an explorer , and the voyages of discovery that resulted from European demand for these products were the basis for building powerful empires .
Today , the same resources are still stimulating the development of new trading societies - - but now those societies are growing inside computers , rather than overseas .
And in watching these artificial societies grow , their inventors are starting their own voyage of discovery - - one they hope will provide insights into real societies that have thus far been denied to conventional social science .
Two of these inventors are Robert Axtell and Joshua Epstein , who work at the Brookings Institution in Washington , DC .
They have created an artificial world they call ' Sugar scape ` .
In it , software ' agents ` of their devising live out their lives .
The agents devised by Dr Axtell and Dr Epstein appear on a computer screen as little red dots which move over a 50 by 50 grid .
Each is actually a piece of software running inside the computer .
But , like people in a real society , the Sugarscape agents are not identical .
They have different visual abilities and different demands for sugar .
The computer landscape has two mountains of a resource , called ' sugar ` , which the agents require .
All of them follow the same rules: look around , go to the unoccupied spot with the largest amount of sugar , and then eat the sugar .
The sugar , when consumed , grows back at a pre - determined rate .
When only sugar is present , the agents ' behaviour is boringly predictable .
Most of them cluster in the sugar mountains .
Only a few of the extremely short - sighted are left out in the cold .
But , having proved their model worked , Dr Axtell and Dr Epstein went on to add complexity to it in the form of a second resource - - ' spice ` .
In this version , the agents require both sugar and spice , but they do not necessarily have to gather their needs directly .
Instead , they may trade with one another .
Each time a trade happens , the computer registers the price of one good in terms of the other .
In the most simple sugar and spice models , the market settles on one price for each commodity .
It does so with no central planning - - a happy story for orthodox economics .
However , as Dr Axtell and Dr Epstein added further complexity to their model the story became messier .
The simple model had agents who never died and whose preferences never changed .
But if old agents are allowed to pass away and be replaced by new ones , and if agents ' preferences for sugar and spice evolve as they interact , the cyber - market never settles on a single price ( just like real life ) .
Sugarscape is not the only agent - based model that has started to explore the pattern of trade .
The agents in a model devised by Deborah Duong ( who works at George Mason University , in Fairfax , Virginia ) , can produce a variety of goods ( she calls them ' oats ` , ' peas ` , ' beans ` and ' barley ` ) .
They , too , can trade .
But they can also vary the amount of each good they produce .
In Ms Duong 's model , each agent quickly learns to tell which other agents sell the produce needed to complement its own diet .
It then adjusts its behaviour accordingly .
When she ran her model , Ms Duong found that it vindicated Adam Smith .
It ended up with a division of labour - - although each agent can ' grow ` the full range of goods if it chooses to , it generally decides that it is more efficient to produce just one and trade it for the others .
Ms Duong 's agents , then , spontaneously organise themselves into a barter economy .
Indeed , they sometimes go further , with one of the goods taking on a money - like quality and being used as a standard of trade .
The next step is to build models that can be tested against the real world .
In one such test Dr Axtell and Dr Epstein have collaborated with George Gumerman , an archaeologist from the Santa Fe Institute in New Mexico , to model the Anasazi society .
This was a culture that flourished in the American Southwest for hundreds of years , built astonishing cliff dwellings , and then vanished .
But the simulation has not yet found the reason why it did so .
Rather than disappearing , computer - based versions of Anasazi society sometimes go on .
And on , and on , and on , and on . . .