Courses/CS 461/Winter 2006/Brian Smith/Week 3

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[edit] Segregation Fields model with individual choice

I didn't have the time this week to devote to NetLogo, so I've posted the new version of my Segregation Fields model. This one expands on the previous versions with the option to allow all people to have an individual desired similarity percentage. The people are represented by arrows, and the direction of the arrows indicates this individual percentage. Pointing directly up (0%), and they can be rotated clockwise to directly downwards (100%). The colors function the same way as previous versions.

[edit] original description

This model expands on Schelling's Segregation by giving unhappy people some intelligence in choosing a new location. In the existing model unhappy people move to a random spot--even if the new spot has far more different neighbors than their comfort threshold. Not only will this person move again, but all the new neighbors (that were in a comfortable neighborhood) also move away, perhaps to undesireable locations. This unfortunately means that the model runs much longer than necessary. This behavior also seems unrealistic to me when trying to model segregation.

In the new model each person generates a field that affects its patch and neighboring patches. For red people these patches take on a red color, and green people generate green patches. The field is diffused once to spread the values to neighboring patches, including empty patches. When an unhappy person is moving they pick a random empty patch with a field that matches their color. This provides a much higher chance that their new location will be desirable and they will stay. It also prevents a person from moving into an area with a high number of people of the opposite color.

For example, let's say we create 2000 people who desire 100% of their neighbors to be their color. In the Schelling model the random moves mean that people stay scattered: percent similar stays at 50% and percent unhappy stays at 97%. In the new fields model groups begin to form in the first few steps signified by red or green shades in the background. Unhappy people move to the edges of these groups and the field becomes stronger. Eventually the only people moving are on the black borders between red and green and they eventually settle down in desireable spots. If we increase the count to 2500 people, there isn't enough empty space to create black borders and the people on the edges never stop moving.

Applet and Source code