  
Slime
Source Code
What
is it?
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This project is inspired by the aggregation behavior of slime-mold
cells. It shows how creatures can aggregate into clusters
using a very decentralized strategy, without any "leader"
involved. In this example, each creature drops a chemical
pheromone (shown in green). The creatures also "sniff" ahead,
trying to follow the gradient of the chemical. Meanwhile,
the patches diffuse and evaporate the chemical. Following
these simple, decentralized rules, the creatures aggregate
into clusters.
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How
to Use It |
Click the setup button to set up a collection of slime-mold
cells. Click the go button to start the simulation.
The number slider controls the number of slime mold
cells. Changes in the slider do not have any effect
until the next setup command.
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Things
to Notice |
With 100 creatures, not much happens. The creatures wander
around, dropping chemical. But the chemical evaporates and
diffuses fairly quickly, and the creatures do not aggregate.
With 500 creatures, following the exact same rules, the result
is qualitatively different. When a few creatures happen (by
chance) to wander near one another, they create a "puddle"
of chemical. The creatures sniff the chemical and try to stay
nearby. They then deposit more chemical in the puddle, so
the puddle expands and attracts more creatures. This process
is a good example of positive feedback: the more creatures,
the larger the puddle, and the larger the puddle, the more
likely it is to attract more creatures.
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Explorations |
- Modify
the program so that the creatures aggregate into a single
large cluster more quickly.
- How
do the results change if there is more (or less) randomness
in the creatures' motion?
- What
"critical number" of creatures is needed for the clusters
to form? How does the critical number change if you modify
the evaporation or diffusion rate?
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StarLogo
Features |
In the uphill procedure, the turtle "follows the gradient"
of the chemical. That is, it "sniffs" in three directions, then
turns in the direction where the chemical is strongest. The
uphill procedure can be useful in many other projects. You might
want to try variants of the uphill procedure, changing the number
and placement of "turtle sniffs."
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We
welcome your feedback and suggestions! Please send us email.
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