globals [ history ;; the history of which number was the minority (encoded into a binary number) complete-history ;; (stored as a binary number) minority ;; the current number in the minority ticks ;; keeps track of time avg-score ;; keeps track of the turtles' average score (0-minority 1-majority) stdev-score ;; keeps tracks of the standard deviation of the turtles' scores (0-minority 1-majority) majority-preferer-number ;; number of turtles which prefer majority ] turtles-own [ score ;; each turtle's score choice ;; each turtle's choice strategies ;; each turtle's strategies (a list of lists) current-strategy ;; each turtle's current strategy (index in above list) strategies-scores ;; the accumulated virtual scores for each of the turtle's strategies (a list) preference ;; whether turtle wants to be in minority or majority ] ;; setup procedure to setup ca if (memory = 1 and strategies-per-agent > 4 ) ;; prevent an infinite loop from occurring [ user-message "You need to increase the memory variable or\n" + "decrease the strategies-per-agent variable" stop ] initialize-system initialize-turtles update-system setup-plots end ;; resets state variables to initialize-system set history random (2 ^ memory) set complete-history binary ( history ) set ticks 0 set avg-score [0 0] set stdev-score [0 0] set majority-preferer-number (floor( majority-preferer-percentage * number)) end ;; creates the specified number of turtles to initialize-turtles cct number [ setxy 0 (world-height * who / number) ;; disperse over the y-axis set heading 90 assign-strategies set current-strategy random strategies-per-agent set choice item history (item current-strategy strategies) ifelse (color-by = "choice") [ recolor-by-choice ] [ set color green ] ;; we initially set all to green to prevent divide by zero error set score 0 set strategies-scores n-values strategies-per-agent [0] assign-preference] end ;; gives the turtles their preference ;; preference=1 means that turtle likes majority to assign-preference ;; turtle procedure ifelse (majority-preferer-number > 0) [set majority-preferer-number (majority-preferer-number - 1) set preference 1] [set preference 0] end ;; gives the turtles their allotted number of unique strategies to assign-strategies ;; turtle procedure set strategies [] while [ length remove-duplicates strategies < strategies-per-agent ] [ set strategies n-values strategies-per-agent [create-strategy] ] end ;; reports a random strategy (a list of 1 or 0's) to-report create-strategy report n-values (2 ^ memory) [random 2] end to setup-plots clear-all-plots set-current-plot "Number Picking Zero" set-plot-y-range 0 number set-current-plot "Success Histogram Minority" set-histogram-num-bars 25 set-current-plot "Success Histogram Majority" set-histogram-num-bars 25 do-plots ;; plot initial values end to do-plots do-plot 0 do-plot 1 end to go no-display ;; we turn off the display temporarily to speed up the model ask turtles [ update-scores-and-strategy ] advance-system ask turtles [ update-choice-and-color ] update-system do-plots move-turtles display end ;; moves the turtles about the world (a visual aid to see their collective behavior) to move-turtles ask turtles with [preference = 0] [ fd score / item 0 avg-score ] ask turtles with [preference = 1] [ fd score / item 1 avg-score ] end ;; updates minority, avg-score, and stdev-score globals to update-system let num-picked-zero count turtles with [choice = 0] ifelse (num-picked-zero <= (number - 1) / 2) [ set minority 0 ] [ set minority 1 ] ;; plot this here for speed or optimization let num-picked-zero-minority count turtles with [choice = 0 and preference = 0] let num-picked-zero-majority count turtles with [choice = 0 and preference = 1] set-current-plot "Number Picking Zero" set-current-plot-pen "minority" plot num-picked-zero-minority set-current-plot-pen "majority" plot num-picked-zero-majority set-current-plot-pen "total" plot num-picked-zero set avg-score replace-item 1 avg-score mean values-from turtles with [preference = 1] [score] set avg-score replace-item 0 avg-score mean values-from turtles with [preference = 0] [score] set stdev-score replace-item 0 stdev-score standard-deviation values-from turtles with [preference = 0] [score] set stdev-score replace-item 1 stdev-score standard-deviation values-from turtles with [preference = 1] [score] end ;; advances the system forward in time and updates the history to advance-system set history decimal (lput minority but-first full-history) set complete-history (lput minority complete-history) set ticks ticks + 1 end ;; updates turtle's score and their strategies' virtual scores to update-scores-and-strategy ;; turtles procedure increment-scores let max-score max strategies-scores let max-strategies [] let counter 0 ;; this picks a strategy with the largest virtual score foreach strategies-scores [ if (? = max-score) [ set max-strategies lput counter max-strategies ] set counter counter + 1 ] set current-strategy one-of max-strategies ifelse (choice = minority) [ if (preference = 0) [set score score + 1] ] [ if (preference = 1) [set score score + 1] ] end ;; this increases the virtual scores of each strategy ;; that selected the right preference to increment-scores ;; turtles procedure ;; here we use MAP to simultaneously walk down both the list ;; of strategies, and the list of those strategies' scores. ;; ?1 is the current strategy, and ?2 is the current score. ;; For each strategy, we check to see if that strategy selected ;; the minority. If it did, we increase its score by one, ;; otherwise we leave the score alone. ifelse (preference = 0) [set strategies-scores (map [ifelse-value (item history ?1 = minority) [?2 + 1] [?2]] strategies strategies-scores)] [set strategies-scores (map [ifelse-value (item history ?1 = minority) [?2] [?2 + 1]] strategies strategies-scores)] end ;; updates turtle's choice and re-colors them to update-choice-and-color ;; turtles procedure set choice (item history (item current-strategy strategies)) ifelse (color-by = "choice") [ recolor-by-choice ] [ recolor-by-success ] end to recolor-by-choice ;; turtles procedure ifelse (preference = 0) [ifelse (choice = 0) [ set color red ] [ set color orange] ] [ifelse (choice = 0) [ set color blue ] [ set color violet ] ] end to recolor-by-success ;; turtles procedure ifelse (preference = 0) [ifelse (score > item 0 avg-score + item 0 stdev-score) [ set color red ] [ ifelse (score < item 0 avg-score - item 0 stdev-score) [ set color yellow ] [ set color orange ] ] ] [ifelse (score > item 1 avg-score + item 1 stdev-score) [ set color blue ] [ ifelse (score < item 1 avg-score - item 1 stdev-score) [ set color pink ] [ set color violet ] ] ] end ;; updates the plots three of the four plots. one is updated in the update-system procedure to do-plot [given-preference] let max-score max values-from turtles with [preference = given-preference] [score] let min-score min values-from turtles with [preference = given-preference] [score] ifelse (given-preference = 0) [set-current-plot "Success Rate Minority"] [set-current-plot "Success Rate Majority"] if (ticks != 0) [ set-current-plot-pen "max" plot max-score / ticks set-current-plot-pen "min" plot min-score / ticks set-current-plot-pen "avg" plot item given-preference avg-score / ticks ifelse (given-preference = 0) [set-current-plot "Success Histogram Minority"] [set-current-plot "Success Histogram Majority"] histogram-from turtles with [preference = given-preference] [score / ticks] ifelse (given-preference = 0) [set-current-plot "Scores Minority"] [set-current-plot "Scores Majority"] set-current-plot-pen "max" plot max-score set-current-plot-pen "min" plot min-score set-current-plot-pen "avg" plot item given-preference avg-score ] end ;; reports the history in binary format (with padding if needed) to-report full-history report (n-values (memory - length binary history) [0] + binary history) end to-report all-history report complete-history end ;; converts a decimal number to a binary number (stored in a list of 0's and 1's) to-report binary [decimal-num] let binary-num [] loop [ set binary-num fput (decimal-num mod 2) binary-num set decimal-num int (decimal-num / 2) if (decimal-num = 0) [ report binary-num ] ] end ;; converts a binary number (stored in a list of 0's and 1's) to a decimal number to-report decimal [binary-num] report reduce [(2 * ?1) + ?2] binary-num end ; *** NetLogo 3.1.3 Model Copyright Notice *** ; ; This model was created as part of the projects: ; PARTICIPATORY SIMULATIONS: NETWORK-BASED DESIGN FOR SYSTEMS LEARNING IN ; CLASSROOMS and/or INTEGRATED SIMULATION AND MODELING ENVIRONMENT. ; The project gratefully acknowledges the support of the ; National Science Foundation (REPP & ROLE programs) -- ; grant numbers REC #9814682 and REC-0126227. ; ; Copyright 2004 by Uri Wilensky. All rights reserved. ; ; Permission to use, modify or redistribute this model is hereby granted, ; provided that both of the following requirements are followed: ; a) this copyright notice is included. ; b) this model will not be redistributed for profit without permission ; from Uri Wilensky. ; Contact Uri Wilensky for appropriate licenses for redistribution for ; profit. ; ; To refer to this model in academic publications, please use: ; Wilensky, U. (2004). NetLogo Minority Game model. ; http://ccl.northwestern.edu/netlogo/models/MinorityGame. ; Center for Connected Learning and Computer-Based Modeling, ; Northwestern University, Evanston, IL. ; ; In other publications, please use: ; Copyright 2004 Uri Wilensky. All rights reserved. ; See http://ccl.northwestern.edu/netlogo/models/MinorityGame ; for terms of use. ; ; *** End of NetLogo 3.1.3 Model Copyright Notice *** @#$#@#$#@ GRAPHICS-WINDOW 630 19 955 365 17 17 9.0 1 10 1 1 1 0 1 1 1 -17 17 -17 17 CC-WINDOW 5 629 964 724 Command Center 0 BUTTON 33 10 102 43 setup setup NIL 1 T OBSERVER NIL NIL BUTTON 107 10 170 43 go go T 1 T OBSERVER NIL NIL SLIDER 17 50 189 83 number number 1 1501 5 2 1 NIL SLIDER 17 87 189 120 memory memory 1 12 4 1 1 NIL SLIDER 17 124 189 157 strategies-per-agent strategies-per-agent 1 10 10 1 1 NIL PLOT 220 395 417 545 Success Rate Minority time success rate 0.0 1.0 0.0 0.05 true true PENS "max" 1.0 0 -2674135 true "min" 1.0 0 -13345367 true "avg" 1.0 0 -10899396 true PLOT 670 396 876 546 Number Picking Zero time count 0.0 1.0 0.0 100.0 true true PENS "minority" 1.0 0 -2674135 true "majority" 1.0 0 -13345367 true "total" 1.0 0 -16777216 true MONITOR 0 566 942 615 History all-history 3 1 PLOT 4 394 207 544 Scores Minority time score 0.0 1.0 0.0 1.0 true true PENS "max" 1.0 0 -2674135 true "min" 1.0 0 -13345367 true "avg" 1.0 0 -10899396 true CHOOSER 243 106 335 151 color-by color-by "choice" "success" 1 PLOT 430 395 631 545 Success Histogram Minority success frequency 0.0 1.0 0.0 1.0 true false PENS "default" 0.02 1 -16777216 false SLIDER 16 170 275 203 majority-preferer-percentage majority-preferer-percentage 0 1 0.5 0.01 1 NIL PLOT 6 226 206 376 Scores Majority time score 0.0 10.0 0.0 10.0 true true PENS "max" 1.0 0 -2674135 true "min" 1.0 0 -13345367 true "avg" 1.0 0 -10899396 true PLOT 429 226 629 376 Success Histogram Majority success frequency 0.0 1.0 0.0 10.0 true false PENS "default" 1.0 1 -16777216 true PLOT 218 226 418 376 Success Rate Majority success rate time 0.0 10.0 0.0 1.0 true true PENS "max" 1.0 0 -2674135 true "min" 1.0 0 -13345367 true "avg" 1.0 0 -10899396 true @#$#@#$#@ WHAT IS IT? ----------- This is a simplified model of what takes place in an economic market. In each time step, agents choose one of two sides, 0 or 1, and those on the minority side win a point. This problem is inspired by the "El Farol" bar problem. Each agent uses a finite set of strategies to make their decision based upon past record; however, the record consists only of which side, 0 or 1, was in the minority, not the actual population count of how many chose each side. HOW IT WORKS ------------ Each agent begins with a score of 0 and STRATEGIES-PER-AGENT strategies. Initially, they choose a random one of these strategies to use. The initial historical record is generated randomly. If their current strategy correctly predicted whether 0 or 1 would be the minority, they add one point to their score. Each strategy also earns virtual points according to if it would have been correct or not. From then on, the agents will then use their strategy with the highest virtual point total to predict whether they should select 0 or 1. This strategy consist of a list of 1's and 0's that is 2^MEMORY long. The choice the turtle then makes is based off of the history of past choices. This history is also a list of 1's and 0's that is MEMORY long, but it is encoded into a binary number. The binary number is then used as an index into the strategy list to determine the choice. This means that once the number of agents, the number of strategies, and the length of the historical record are chosen, all parameters are fixed and the behavior of the system is of interest. HOW TO USE IT ------------- GO: Starts and stops the model. SETUP: Resets the simulation according to the parameters set by the sliders. NUMBER: Sets the number of agents to participate. This is always odd to insure a minority. MEMORY: Sets the length of the history which the agents use to predict their behavior. Most interesting between 3 and 12, though there is some interesting behavior at 1 and 2. Note that when using a MEMORY of 1, the STRATEGIES-PER-AGENT needs to be 4 or less. STRATEGIES-PER-AGENT: Sets the number of strategies each agent has in their toolbox. Five is typically a good value. However, this can be changed for investigative purposes using the slider, if desired. COLOR-BY: "Choice" represents the agents changing their colors depending on if they have chosen 0 (red) or 1 (blue). "Success" represents the agents changing their color depending upon their success rate (the number of times they have been in the minority divided by the number of selections). An agent is green if they are within one standard deviation above or below the mean success rate, red if they are more than one standard deviation above, and blue if they are more than one standard deviation below. **RECOMMENDED SETTINGS: NUMBER=501, MEMORY=6, STRATEGIES-PER-AGENT=5 (Should be loaded by default) **CAUTION: If you are on a slow computer and the model is likewise slow, try turning off the shapes in the view. You could also turn off the view as the plots show everything the view does, just in a different representation. Also, beware setting the MEMORY slider to higher values. It scales exponentially (2^MEMORY), however this only has an affect when SETUP is run. This means that for each increased unit of MEMORY, it takes twice as long for SETUP to run. THINGS TO NOTICE ---------------- There are two extremes possible for each turn: the size of the minority is 1 agent or (NUMBER-1)/2 agents (since NUMBER is always odd). The former would represent a "wasting of resources", while the latter represents a situation which is more "for the common good." However, each agent acts in an inherently selfish manner, as they care only if they and they alone are in the minority. Nevertheless, the latter situation is prevalent. Does this represent unintended cooperation between agents, or merely coordination and well developed powers of prediction? The agents move according to how successful they are relative to the mean success rate. After running for about 100 time steps (at just about any parameter setting), how do the fastest and slowest agents compare? What does this imply? THINGS TO TRY ------------- Notice how the population of agents choosing 0 stays close to NUMBER/2. How do the deviations change as you change the value of MEMORY? How do things change if you keep everything the same but change the STRATEGIES-PER-AGENT? EXTENDING THE MODEL ------------------- There are a few evolutionary possibilities for this model which could be coded. (1) Maybe after some (long) amount of time, the least successful agent is replaced by a clone of the most successful agent, with zeroed scores and possibly mutated strategies. How would things change then? (2) Similar to (1), you could start the agents with a very small memory value, and again replace the least successful agent with a clone of the most successful agent. But this time instead of just zeroing the scores and giving mutated strategies, you also add or subtract one unit of memory for the new agent. What would happen here? Would their brains continue to get bigger or find some happy value? Would people with small memory be altogether eliminated, or would they survive (maybe even still thrive)? NETLOGO FEATURES ---------------- One feature which was instrumental to this program was the n-values primitive. When setting up strategies for each player, they are binary numbers (stored in lists) of 2^MEMORY values. If this was done by starting with an empty list and calling fput 2^MEMORY times for each agent and for each strategy, you are calling fput NUMBER * STRATEGIES-PER-AGENT * (2^MEMORY) times. Using n-values sped this up by about 2 or 3 orders of magnitude. The primitives map and reduce were also used to simplify code. RELATED MODELS -------------- Any of the Prisoner's Dilemma models Altruism Cooperation CREDITS AND REFERENCES ---------------------- Original implementation: Daniel B. Stouffer, for the Center for Connected Learning and Computer-Based Modeling. This model was based upon studies by Dr. Damien Challet, et al. Information can be found on the web at http://www.unifr.ch/econophysics/minority/ Challet, D. and Zhang, Y.-C. Emergence of Cooperation and Organization in an Evolutionary Game. Physica A 246, 407 (1997). Zhang, Y.-C. Modeling Market Mechanism with Evolutionary Games. Europhys. News 29, 51 (1998). To refer to this model in academic publications, please use: Wilensky, U. (2004). NetLogo Minority Game model. http://ccl.northwestern.edu/netlogo/models/MinorityGame. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL. In other publications, please use: Copyright 2004 Uri Wilensky. All rights reserved. See http://ccl.northwestern.edu/netlogo/models/MinorityGame for terms of use. @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 link true 0 Line -7500403 true 150 0 150 300 link direction true 0 Line -7500403 true 150 150 30 225 Line -7500403 true 150 150 270 225 airplane true 0 Polygon -7500403 true true 150 0 135 15 120 60 120 105 15 165 15 195 120 180 135 240 105 270 120 285 150 270 180 285 210 270 165 240 180 180 285 195 285 165 180 105 180 60 165 15 arrow true 0 Polygon -7500403 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 box false 0 Polygon -7500403 true true 150 285 285 225 285 75 150 135 Polygon -7500403 true true 150 135 15 75 150 15 285 75 Polygon -7500403 true true 15 75 15 225 150 285 150 135 Line -16777216 false 150 285 150 135 Line -16777216 false 150 135 15 75 Line -16777216 false 150 135 285 75 bug true 0 Circle -7500403 true true 96 182 108 Circle -7500403 true true 110 127 80 Circle -7500403 true true 110 75 80 Line 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