The applet requires Java 1.4.1 or higher. It will not run on Windows 95 or Mac OS 8 or 9. Mac users must have OS X 10.2.6 or higher and use a browser that supports Java 1.4. (Safari works, IE does not. Mac OS X comes with Safari. Open Safari and set it as your default web browser under Safari/Preferences/General.) On other operating systems, you may obtain the latest Java plugin from Sun's Java site.
powered by NetLogo
view/download model file: village_evolution_and_warehouse_effect.nlogo
The model is about the observation of two prehistoric populations that collect food in their two villages. The main issue is to show the role played by the warehouse and the skill to preserve food that just one of the two villages has.
The model has been builted using a combination of NetLogo turtles and patches. There are three agentsets: men, gnus and villages. Men can eat gnus and barries to reproduce themselves; gnus can just eat grass to reproduce themselves; villages are different because one of them own the warehouse while other don't. Patches can represent grass, berries or sand.
The model starts when the "setup" button is pressed. In this way the user creates the prehistoric world with the agentsets and patches above-cited. Next step is to press the "go" button. So the user can see men that go around to hunt gnus or collect berries, gnus who move to eat grass and patches that change color continuously.
If you want to change the number of men or the number of gnus, move the NUMBER_OF_MEN or the NUMBER_OF_GNUS slider before pressing "setup". The DISTANCE? slider sets the maximum ditance that every man can reach. The VEGETAL_MEDIUM_GROW slider sets the growth speed of grass and barries in the world. The CAPITALISTIC_FACTOR? slider sets the daily level of energy that every man of village 1 has to leave in the warehouse. The BIRTH_THRESHOLD slider sets the energy that every man has to own to reproduce himself. If you want to see the differences between a capitalistic world and a communist world you can operate the on-off CAPITALISTIC_WORLD? switch. Finally you can turn on the GRASS_CONCENTRATION? switch if you like to show that the grass concentrates in a particular area of the world.
It's interesting to see the dinamics of the two populations along several years.The important thing to underline is that the orange population you can see on the graph is the one with warehouse so, in the capitalistic world, you should notice that this population grows more than the yellow one. It' also interesting to notice the different level of energy that the populations can reach and also in this case the orange population should have more energy than the yellow one due to the presence of the warehouse in its village. The third main thing one has to notice is the number of deaths in each village. These are the three more interesting aspects one has to see to notice the impact of the warehouse on the model.
The first thing one can do is to change the nature of the world. This mean that it's interesting to notice the different dinamics of the populations in the capitalistic and communist world. It's easy to pass to one world to the other: the user has just to push the switch called CAPITALISTIC_WORLD?. Another useful experiment is about to move the slider of the maximum distance that men can reach in the model. The distance is important because affects the number of gnus that a man can reach and hunt, moreover affects the energy and the populations of the villages.
We try to include in the model two periods of year, one in which the crop is good and one period of crisis. This is an attempt to create a more realistic world but it isn't complete and a little rough in the way it has been builted. So the model can be corroborated by the substitution of these two periods with seasons to get it more realistic.
The models we referred to are some predations models one can find into the NetLogo models library as indicated in the credits and references space.
In developing our model we use some models in the NetLogo models library. In particular we used Ants and Wolf sheet predation as our two main models. They both were useful to understand the ways agents interact.
This model was developed by Nicola Giuliano and Alessandro Graniero, students of the University of Turin, Faculty of Economics. See http://web.econ.unito.it/terna/tesine for other related student's project works.