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 ` ) .

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 . . .

---