# Heros and Cowards (emergence extension)

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## ACKNOWLEDGMENT

This model is a minor but interesting variation on a model from from Chapter Two of the book "Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo", by Uri Wilensky & William Rand.

* Wilensky, U. & Rand, W. (2015). Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo. Cambridge, MA. MIT Press.

This original model is in the IABM Textbook folder of the NetLogo Models Library. The model, as well as any updates to the model, can also be found on the textbook website: http://www.intro-to-abm.com/.

Most of this info is from the "Hero's and Cowards" model. I have added a few comments here and there. Indicated by ;; comment RDM

## UPDATES TO THE MODEL SINCE TEXTBOOK PUBLICATION

In the textbook version of the code, there is a slight chance that a turtle's friend is also its enemy. Here, we prevent this from happening by choosing the enemy of a turtle amongst the set of other turtles not including its friend.

Also, we could not resist adding a few interesting preset configurations. Have fun playing with them!

## WHAT IS IT?

The "Heroes and Cowards" game, also called the "Friends and Enemies" game or the "Aggressors and Defenders" game dates back to the Fratelli Theater Group at the 1999 Embracing Complexity conference, or perhaps earlier.

In the human version of this game, each person arbitrarily chooses someone else in the room to be their perceived friend, and someone to be their perceived enemy. They don't tell anyone who they have chosen, but they all move to position themselves either such that a) they are between their friend and their enemy (BRAVE/DEFENDING), or b) such that they are behind their friend relative to their enemy (COWARDLY/FLEEING).

This simple model demonstrates an idealized form of this game played out by computational agents. Mostly it demonstrates how rich, complex, and surprising behavior can emerge from simple rules and interactions.

## HOW IT WORKS

The rules of this model are that there are two basic personality types. All agents in the model choose a friend and an enemy. If their personality is BRAVE, then the agent tries to stay between their enemy and their friend, protecting their friend. If their personality is COWARDLY, then the agent tries to keep their friend between them and their enemy, hiding behind their friend.

## HOW TO USE IT

Choose the NUMBER of turtles you want to examine, and choose whether the turtles should act COWARDLY, BRAVE, or MIXED. Then press SETUP followed by GO to observe the patterns of behavior formed.

## THINGS TO NOTICE

Run the model many times and observe the different patterns of behavior.

INSPECT or WATCH some turtles so that you can see their individual behavior.

## THINGS TO TRY

Can you find new cool configurations with 68 turtles? How many different type can you find? What happens when you vary the number of turtles?

## EXTENDING THE MODEL

There is a bug we deliberately introduced in the SETUP of the model. Can you find it and fix it? Once you have fixed it, how does it affect the preset configurations?

Can you find new presets?

I believe I fixed the bug at least in this version RDM.

Modify the code to add more control over how many of each type of behavior there is.

Change the world wrapping rules to see how that effects the results.

You can create buttons that capture interesting patterns of behaviors by using the RANDOM-SEED function in NetLogo. First set the RANDOM-SEED to different values. PRESS SETUP then GO and observe the behaviors. We created a `preset` procedure that makes it easy to create your own buttons that produce interesting behaviors. This procedure assumes a population of 68 turtles with "mixed" behaviors, but you could modify it to allow different settings. Create your own buttons that produce interesting behaviors.

I added a couple of very cool buttons that basically introduce a degree of order. As party goers arrive the person that arrives just before them is their friend and just after their enemy. For LinearWrap this resembles a circular buffer, while for LinearNoWrap this resembles a queue. RDM

I also added gender, which was not too interesting as well as links which were informative. Red links are to enemies, blue to friends. RDM

## NETLOGO FEATURES

RANDOM-SEED initializes the NetLogo random number generator so that it always produces the same set of random numbers, enabling exact reproduction of model runs.

## CREDITS AND REFERENCES

Versions of the Model are described in:

Bonabeau, E., & Meyer, C. (2001). Swarm intelligence. A whole new way to think about business. Harvard Business Review, 5, 107-114.

Bonabeau. E. (2012). http://www.icosystem.com/labsdemos/the-game/ .

Bonabeau, E., Funes, P. & Orme, B. (2003). Exploratory Design Of Swarms. 2nd International Workshop on the Mathematics and Algorithms of Social Insects. Georgia Institute of technology, Atlanta, GA.

Sweeney, L. B., & Meadows, D. (2010). The systems thinking playbook: Exercises to stretch and build learning and systems thinking capabilities.

## HOW TO CITE

This model is part of the textbook, “Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo.”

If you mention this model or the NetLogo software in a publication, we ask that you include the citations below.

For the model itself:

* Stonedahl, F., Wilensky, U., Rand, W. (2014). NetLogo Heroes and Cowards model. http://ccl.northwestern.edu/netlogo/models/HeroesandCowards. Center for Connected Learning and Computer-Based Modeling, Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL.

Please cite the NetLogo software as:

* Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

Please cite the textbook as:

* Wilensky, U. & Rand, W. (2015). Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo. Cambridge, MA. MIT Press.

## COPYRIGHT AND LICENSE

Copyright 2014 Uri Wilensky.

![CC BY-NC-SA 3.0](http://ccl.northwestern.edu/images/creativecommons/byncsa.png)

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.

Commercial licenses are also available. To inquire about commercial licenses, please contact Uri Wilensky at uri@northwestern.edu.

## Comments and Questions

turtles-own [ friend enemy ] breed [females female] breed [males male] globals [i] undirected-link-breed [red-links red-link] undirected-link-breed [blue-links blue-link] to setup ;;Minor change added male and females (gender) RDM clear-all ask patches [ set pcolor white ] ;; create a blank background create-females number [ setxy random-xcor random-ycor set shape "circle" set size 0.5 ;; set the turtle personalities based on chooser if (personalities = "brave") [ set color magenta ] if (personalities = "cowardly") [ set color green ] if (personalities = "mixed") [ set color one-of [ green magenta ] ] if (personalities = "mixed25Coward") [ set color one-of [ green green magenta ] ] if (personalities = "mixed75Coward") [ set color one-of [ green magenta magenta ] ] ;; choose friend and enemy targets set friend one-of other females set enemy one-of other females create-red-link-with enemy [set color red] ;; Links added RDM create-blue-link-with friend [set color blue] ;; Links added RDM ] create-males number [ setxy random-xcor random-ycor set shape "circle" set size 0.5 ;; set the turtle personalities based on chooser if (personalities = "brave") [ set color blue ] if (personalities = "cowardly") [ set color red ] if (personalities = "mixed") [ set color one-of [ red blue ] ] if (personalities = "mixed25Coward") [ set color one-of [ red red blue ] ] if (personalities = "mixed75Coward") [ set color one-of [ red blue blue ] ] ;; choose friend and enemy targets set friend one-of other males set enemy one-of other males create-red-link-with enemy [set color red] create-blue-link-with friend [set color blue] ] reset-ticks end to go ask turtles with [color = red or color = blue or color = green or color = magenta] [ ;; print who if (color = blue) [ act-bravely ] if (color = red) [ act-cowardly ] if (color = magenta) [ act-bravely ] if (color = green) [ act-cowardly ] ] tick end to gomf ;; Added male female go routine RDM ask males with [color = red or color = blue] [ ;; print who if (color = blue) [ act-bravely ] if (color = red) [ act-cowardly ] ] ask females with [color = green or color = magenta] [ ;; print who if (color = magenta) [ act-bravely ] if (color = green) [ act-cowardly ] ] tick end to act-bravely ;; move toward the midpoint of your friend and enemy facexy ([xcor] of friend + [xcor] of enemy) / 2 ([ycor] of friend + [ycor] of enemy) / 2 ;;fd 0.1 ;;show [count turtles in-radius 1] of self if ([count turtles in-cone 1 60] of self < 20) [fd 0.1] ;; Added simple collision avoidance RDM if ([count turtles in-radius 1] of self > 20) [ facexy random-xcor random-ycor fd 0.1 ] end to act-cowardly ;; put your friend between you and your enemy facexy ([xcor] of friend + [xcor] of friend - [xcor] of enemy) ([ycor] of friend + [ycor] of friend - [ycor] of enemy) ;;fd 0.1 if ([count turtles in-cone 1 60] of self < 20) [fd 0.1] ;; Added simple collision avoidance RDM if ([count turtles in-radius 1] of self > 20) [ facexy random-xcor random-ycor fd 0.1 ] end to preset [ seed ] ;; sets up the model for use with a particular random seed and constant ;; model parameters, so that a particular pattern can be re-created. set personalities "mixed" set number 68 random-seed seed setup end to one ;; Added routine to have one person be everyone's friend and enemy ;; set all friends and enemies to the same turtle ;; also interesting to set friend and enemy to different turtles clear-all ask patches [ set pcolor white ] ;; create a blank background create-turtles number [ setxy random-xcor random-ycor ;; set the turtle personalities based on chooser if (personalities = "brave") [ set color blue ] if (personalities = "cowardly") [ set color red ] if (personalities = "mixed") [ set color one-of [ red blue ] ] if (personalities = "mixed25Coward") [ set color one-of [ red red blue ] ] if (personalities = "mixed75Coward") [ set color one-of [ red blue blue ] ] ;; choose friend and enemy targets set friend turtle 1 set enemy turtle 1 ] reset-ticks end to linearWrap ;; Added Linear Wrap around or circular buffer order RDM ;; set all friend of turtle i to i+1 and enemy to i-1 ;; connect first and last turtle clear-all ask patches [ set pcolor white ] ;; create a blank background create-turtles number [ setxy random-xcor random-ycor ;; set the turtle personalities based on chooser if (personalities = "brave") [ set color blue ] if (personalities = "cowardly") [ set color red ] if (personalities = "mixed") [ set color one-of [ red blue ] ] if (personalities = "mixed25Coward") [ set color one-of [ red red blue ] ] if (personalities = "mixed75Coward") [ set color one-of [ red blue blue ] ] ;; choose friend and enemy targets set i 1 while [i < (number - 1)] [ ask turtle i [set friend turtle (i + 1)] ask turtle i [create-link-with (friend) [set color blue]] ask turtle i [set enemy turtle (i - 1)] ask turtle i [create-link-with (enemy) [set color red]] set i i + 1 ] ask turtle (number - 1 ) [set friend turtle 0] ask turtle (number - 1 ) [set enemy turtle (number - 2)] ask turtle 0 [set enemy turtle (number - 1)] ask turtle 0 [set friend turtle 1 ] ] reset-ticks end to linearNoWrap ;; Added Linear No Wrap around or queue order RDM ;; set all friend of turtle i to i+1 and enemy to i-1 ;; do not connect first and last turtle clear-all ask patches [ set pcolor white ] ;; create a blank background create-turtles number [ setxy random-xcor random-ycor ;; set the turtle personalities based on chooser if (personalities = "brave") [ set color blue ] if (personalities = "cowardly") [ set color red ] if (personalities = "mixed") [ set color one-of [ red blue ] ] if (personalities = "mixed25Coward") [ set color one-of [ red red blue ] ] if (personalities = "mixed75Coward") [ set color one-of [ red blue blue ] ] ;; choose friend and enemy targets set i 1 while [i < (number - 1)] [ ask turtle i [set friend turtle (i + 1)] ask turtle i [create-link-with (friend) [set color blue]] ask turtle i [set enemy turtle (i - 1)] ask turtle i [create-link-with (enemy) [set color red]] set i i + 1 ] ask turtle (number - 1 ) [set friend turtle (number - 1 )] ask turtle (number - 1 ) [set enemy turtle (number - 2) ] ask turtle 0 [set enemy turtle 0 ] ask turtle 0 [set friend turtle 1 ] ] reset-ticks end ; Copyright 2014 Uri Wilensky. ; See Info tab for full copyright and license.

There is only one version of this model, created over 2 years ago by Bob McLeod.

## Attached files

File | Type | Description | Last updated | |
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Heros and Cowards (emergence extension).png | preview | Preview for 'Heros and Cowards (emergence extension)' | over 2 years ago, by Bob McLeod | Download |

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