globals [partner-is-silent?] to setup ca ;;Build the jail cell ask patches with [(abs pxcor) = screen-edge-x or (abs pycor) = screen-edge-y] [ set pcolor grey] ;;make the face visible cct 1 [set size 30 set shape "face"] ;; set up the prisoner's dillema ifelse partner-silence-known? [ set partner-is-silent? partner-silent? ] [ ;;if partner silence is not known, choose randomly whether or not he is silent. ifelse random 2 = 0 [ set partner-is-silent? true ] [ set partner-is-silent? false ] ] end ;;play the game, changing the face depending on the outcome. to answer setup ;;clears variables away so that setup doesn't need to be pressed every time. ;;next the four possible combinations of choices are dealt with. ;;the result corresponds to the tables in the interface and information tabs. ;;first check to see if your partner was silent. ifelse partner-is-silent? [ ;;now go through your two possible choices ifelse you-silent? [ ask turtles [set shape "silent-face"] user-message "You and your partner both remain silent. You are sentenced one year imprisonment." ] [ ask turtles [set shape "devious-face"] user-message "You confess and your partner remains silent. You go free." ] ] ;;your partner confessed. [ ;;again go through your two possible choices ifelse you-silent? [ ask turtles [set shape "sucker-face" ] user-message "You remain silent, but your partner confesses. You are sentenced five years imprisonment." ] [ ask turtles [set shape "rational-face"] user-message "You and you partner both confess. You are sentenced three years imprisonment." ] ] end ; *** NetLogo Model Copyright Notice *** ; ; This model was created as part of the project: ; PARTICIPATORY SIMULATIONS: NETWORK-BASED DESIGN FOR SYSTEMS LEARNING IN ; CLASSROOMS. The project gratefully acknowledges the support of the ; National Science Foundation (REPP program) -- grant number REC #9814682. ; ; Copyright 2002 by Uri Wilensky. Updated 2002. 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. (2002). NetLogo PD Basic model. ; http://ccl.northwestern.edu/netlogo/models/PDBasic. ; Center for Connected Learning and Computer-Based Modeling, ; Northwestern University, Evanston, IL. ; ; In other publications, please use: ; Copyright 1998 by Uri Wilensky. All rights reserved. See ; http://ccl.northwestern.edu/netlogo/models/PDBasic ; for terms of use. ; ; *** End of NetLogo Model Copyright Notice *** @#$#@#$#@ GRAPHICS-WINDOW 313 -5 673 376 17 17 10.0 1 10 1 1 1 CC-WINDOW 315 380 657 478 Command Center BUTTON 162 115 262 148 NIL answer NIL 1 T OBSERVER T SWITCH 58 214 262 247 partner-silent? partner-silent? 1 1 -1000 BUTTON 58 115 162 148 NIL setup NIL 1 T OBSERVER T SWITCH 58 148 262 181 you-silent? you-silent? 0 1 -1000 SWITCH 58 181 262 214 partner-silence-known? partner-silence-known? 0 1 -1000 TEXTBOX 119 374 300 434 TRUE FALSE\nTRUE 1 year 5 years\nFALSE none 3 years TEXTBOX 14 306 302 336 YOUR JAIL TIME\n-------------------------------------------------------------- TEXTBOX 176 342 298 360 partner-silent? TEXTBOX 21 396 111 414 you-silent? TEXTBOX 8 43 302 99 Decide whether to remain silent or confess and then answer the police to receive your sentence. @#$#@#$#@ UNDERSTANDING THE MODEL ----------------------- You and your partner have been arrested for robbing a bank and find yourselves in the classic prisoner's dilemma. The police place each of you into separate rooms and come to you with the following proposal: "We know you two did this, but don't have proof for anything but a minor charge of firearm possession that will give you a year of jail time. Confess to the robbery and we will make sure the judge goes easy on you, 3 years. If your partner confesses and you don't, we're going to throw the book at you and give you 5 years of prison time. If your partner doesn't and you do, we will let you go free." Should you remain silent or should you confess? How much jail time you will receive depends on your answer and also on your partner's answer to the same question. The following table summarizes the results of the four different situations: | Your Action | Partner's Action | Your Jail Time | Partner's Jail Time |---------------------------------------------------------------------- | Silent Silent 1 1 | Silent Confess 5 0 | Confess Silent 0 5 | Confess Confess 3 3 HOW TO USE IT ------------- SETUP: Place yourself in the prisoner's dilemma ANSWER: Answer the police and receive your sentence. YOU-SILENT?: If you are silent, you will not confess. If you are not silent, you will confess. PARTNER-SILENCE-KNOWN?: When on, this switch allows you to control the actions of your partner with the PARTNER-SILENT? switch. PARTNER-SILENT?: If your partner is silent, he will not confess. If he is not silent, he will confess. THINGS TO TRY ------------- Turn off PARTNER-SILENCE-KNOWN?. Attempt to minimize your prison sentence. Can you do better than your partner? Why or why not? What strategy is best for the group as a whole? Describe a real life scenario that is similar to the prisoner's dilemma, preferably one from your own life. What was the best decision? Why? EXTENDING THE MODEL -------------------- Examine the PD TWO PERSON ITERATED model. NETLOGO FEATURES ---------------- The use of the USER-MESSAGE primitive to give the prison sentence. The use the SIZE turtle variable and TURTLE SIZES option on the graphics window to make large faces. The use of the SHAPE turtle variable to change the faces. RELATED MODELS -------------- PD TWO PERSON ITERATED PD N-PERSON ITERATED PD BASIC EVOLUTIONARY CREDITS AND REFERENCES ---------------------- To refer to this model in academic publications, please use: Wilensky, U. (2002). NetLogo PD Basic model. http://ccl.northwestern.edu/netlogo/models/PDBasic. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL. In other publications, please use: Copyright 2002 by Uri Wilensky. All rights reserved. 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