Homework

Ant communication

In this assignment, you'll explore a ant-inspired scenario in which COMMUNICATION can be used to improve foraging efficiency.

To complete this assignment, you will need to modify code in the following template file: hw09_template.nlogo

Answer the questions found on the 'Assignment' tab and email your responses along with a copy of the netlogo file to mcb419@gmail.com with 'hw09' in the Subject line.

This assignment is due by 11:59PM (midnight) on Tue, Apr 14.

Controller

Your goal is to modify the 'trails' search-strategy, so that the ants improve their foraging efficiency via pheromone communication.

This may require changing two aspects of the ants' behavior:

• how an ant deposits pheromone (SENDER FUNCTIONS)
• how an ant responds to pheromone (RECEIVER FUNCTIONS)

You may also need to change the diffusion and evaporation properties of the pheromone via the two sliders on the user interface.

Food

Food is represented by green patches. There are a total of 90 food patches (3 groups of 30). When an ant overlaps a green food patch, it picks up the food and carrys it back to the home nest in the center of the screen. (The retrieved food in the center has a slightly different color, so the ants won't pick up food that has already been deposited in the nest).

Pheromone

The ants deposit pheromone as they are carrying food back to the nest. The pheromone trails show up as shades of orange and white. Two sliders control the diffusion and evaporation properties of the pheromone. In the TEMPLATE VERSION, ants ignore the pheromone trails.

Nest scent

There is also a nest-scent, which is a chemical gradient centered on the home-nest. By performing taxis on the nest-scent gradient, the ants can head directly back to the nest once they find food.

Sensors

The ants have access the the following sensory variables:

  nest-scent:     nest-scent at the ant's current location
  nest-left:      nest-scent at the tip of the left antenna
  nest-right:     nest-scent at the tip of the right antenna
 
  pheromone:      pheromone level at the ant's current location
  pher-left:      pheromone level at the tip of the left antenna
  pher-right:     pheromone level at the tip of the right antenna
 
  carrying-food?: whether or not the ant has food in its mouth (T/F)

Restrictions

In writing your code, you cannot allow your ant to move more than one unit per tick.

Assignment

You can access a copy of the assignment file HERE, or copy and paste from the text below.

=================================================================
MCB 419 Homework 9 (Spring 2009)

When you've finished answering all the questions, email a copy 
of this file (hw09.txt) along with your NetLogo file (hw09.nlogo)
to mcb419@gmail.com with 'hw09' in the Subject line. 

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1. For the 'wander' controller, record the amount of food 
collected at the end of 500 ticks on 5 consecutive trials and 
report the average  value across these 5 trials.

2. Following the guidelines on the 'specs' tab, implement a 
pheromone-based controller ('trails') that allows the ants 
to improve their foraging efficiency. For your final design,
record the food collected at the end of 500 ticks on 5 
consecutive trials and report the average. 
(Target value should be greater than 60.)

3. Briefly describe the strategy that your ants used to
DEPOSIT pheromone (SENDER FUNCTION)

4. Briefly describe how you selected the DIFFUSION and
EVAPORATION rates for the pheromone signal in your model.
Was the overall performance sensitive to these values?

5. Briefly describe the strategy that your ants used in
response to presence of pheromone (RECEIVER FUNCTION).

6. In developing the model, which was more complicated
to implement, the SENDER FUNCTION (rules for depositing
pheromone) or the RECEIVER FUNCTION (rules for responding
to pheromone)?  Which of these two systems would you 
expect to have more complicated neural circuitry in real
ants?

7. What did you find to be the most challenging aspect of 
this assignment?

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END OF THE ASSIGNMENT
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Solution

Solutions will be posted after the due date.