PK ·İMLp
codemeta.json{"@context": ["https://doi.org/doi:10.5063/schema/codemeta-2.0", "http://schema.org"], "@type": "SoftwareSourceCode", "provider": {"url": "https://www.comses.net", "@type": "Organization", "name": "CoMSES Network (CoMSES)", "@id": "https://www.comses.net"}}PK ·İMLĥe~ôX ôX code/truststranger.nlogoglobals
[
R ; payoff from game when agents both cooperate
S ; payoff from game when agent cooperated and other defected
T ; payoff from game when agent defected and other cooperated
P ; payoff from game when both agents defected
nrExit ; number games where agents did not play games
nrCC ; number of games where both agents cooperated
nrDD ; number of games where both agents defected
nrCD ; number of games where one agent cooperated and other defected
avgnrExit
avgnrCC
avgnrDD
avgnrCD
avgalpha
avgbeta
avgpayoff
]
turtles-own
[
alpha ; guilt factor of agent
beta ; pride factor of agent
payoff ; payoff of games played during a generation
w ; weights for the nrsymbols + 1 units of the M function
symbols ; a list of 0 and 1 that represents the symbols of agents. The length of the list is nrsymbols + 1 since item 0 is a constant of the M equation.
nrgames ; nrgames played during a generation
notdrawn? ; is true when agent is drawn and can not be drawn again to determine player B
alphaparent
betaparent
wparent
symbolsparent
]
to setup
;; (for your model to work with NetLogo's new plotting features,
;; __clear-all-and-reset-ticks should be replaced with clear-all at
;; the beginning of your setup procedure and reset-ticks at the end
;; of the procedure.)
__clear-all-and-reset-ticks
set T 2
set R 1
set P -1
set S -2
set nrExit 0
set nrCC 0
set nrDD 0
set nrCD 0
set avgnrExit 0
set avgnrCC 0
set avgnrDD 0
set avgnrCD 0
set avgalpha 0
set avgbeta 0
set avgpayoff 0
let teller 0
set-default-shape turtles "dot"
crt nragents [
set color red
set size 5
let correct 0
while [correct = 0]
[
set alpha random-float 1
set beta random-float 1
if alpha > beta [set correct 1]
]
set xcor (alpha * 100)
set ycor (beta * 100)
set payoff 0
set nrgames 0
set teller 0
set notdrawn? true
set w []
set symbols []
while [teller <= nrsymbols]
[
set w lput 0 w
ifelse teller = 0 [set symbols lput 1 symbols]
[ifelse random-float 1.0 < 0.5 [set symbols lput 1 symbols][set symbols lput 0 symbols]]
set teller teller + 1
]
]
do-plots
end
to go
set nrExit 0
set nrCC 0
set nrDD 0
set nrCD 0
playgames
replacement
ask turtles [
set xcor (alpha * 100)
set ycor (beta * 100)
]
do-plots
ask turtles [
set payoff 0
set nrgames 0
set alphaparent alpha
set betaparent beta
set wparent w
set symbolsparent symbols
]
tick
end
to playgames
let teller 0
let M 0
let EUC 0 ; expected utility to cooperate
let EUD 0 ; expected utility to defect
let tellerS 0
let PTA 0 ; probability agent A has whether agent B will cooperate (trust from A in B)
let PTB 0 ; probability agent B has whether agent A will cooperate (trust from B in A)
let PrC 0 ; probability to cooperate
let decisionA 0
let decisionB 0
let agentA 0
let agentB 0
let payoffA 0
let payoffB 0
let weight 0
while [teller < gamespg]
[
; draw two random agents
set agentA one-of turtles
ask agentA [set notdrawn? false]
set agentB one-of turtles with [notdrawn?]
ask agentA [set notdrawn? true]
; estimate trust of A in B and decision to cooperate or not
set M item 0 [w] of agentA
set tellerS 1
while [tellerS <= nrsymbols]
[
set M M + item tellerS [symbols] of agentB * item tellerS [w] of agentA
set tellerS tellerS + 1
]
set PTA 1 / (1 + e ^ (- M))
set EUC PTA * R + (1 - PTA) * (S + [beta] of agentA * (T - S))
set EUD PTA * (T - [alpha] of agentA * (T - S)) + (1 - PTA) * P
set PrC (e ^ (steepness * EUC)) / ((e ^ (steepness * EUC)) + (e ^ (steepness * EUD)))
ifelse random-float 1.0 < PrC [set decisionA 1][set decisionA 0]
; estimate trust of B in A and decision to cooperate or not
set M item 0 [w] of agentB
set tellerS 1
while [tellerS <= nrsymbols]
[
set M M + item tellerS [symbols] of agentA * item tellerS [w] of agentB
set tellerS tellerS + 1
]
set PTB 1 / (1 + e ^ (- M))
set EUC PTB * R + (1 - PTB) * (S + [beta] of agentB * (T - S))
set EUD PTB * (T - [alpha] of agentB * (T - S)) + (1 - PTB) * P
set PrC (e ^ (steepness * EUC)) / ((e ^ (steepness * EUC)) + (e ^ (steepness * EUD)))
ifelse random-float 1.0 < PrC [set decisionB 1][set decisionB 0]
ask agentA [set nrgames nrgames + 1]
ask agentB [set nrgames nrgames + 1]
; only when both players trust eachother play the game
ifelse ((random-float 1.0 < PTA) and (random-float 1.0 < PTB))
[
if decisionA = 1 and decisionB = 1 [
ask agentA [set payoff payoff + R]
ask agentB [set payoff payoff + R]
set nrCC nrCC + 1]
if decisionA = 1 and decisionB = 0 [
ask agentA [set payoff payoff + S]
ask agentB [set payoff payoff + T]
set nrCD nrCD + 1]
if decisionA = 0 and decisionB = 1 [
ask agentA [set payoff payoff + T]
ask agentB [set payoff payoff + S]
set nrCD nrCD + 1]
if decisionA = 0 and decisionB = 0 [
ask agentA [set payoff payoff + P]
ask agentB [set payoff payoff + P]
set nrDD nrDD + 1]
; update weights symbols due to learning
set tellerS 0
while [tellerS <= nrsymbols]
[
set weight item tellerS [w] of agentA + learningrate * (decisionB - PTA) * item tellerS [symbols] of agentB
ask agentA [set w replace-item tellerS w weight]
set tellerS tellerS + 1
]
set tellerS 0
while [tellerS <= nrsymbols]
[
set weight item tellerS [w] of agentB + learningrate * (decisionA - PTB) * item tellerS [symbols] of agentA
ask agentB [set w replace-item tellerS w weight]
set tellerS tellerS + 1
]
][set nrExit nrExit + 1]
set teller teller + 1
]
end
to replacement
let tellerS 0
let agentA 0
let agentB 0
ask turtles [
set alphaparent alpha
set betaparent beta
set symbolsparent symbols
set wparent w
ifelse nrgames > 0
[set payoff payoff / nrgames][set payoff 0]]
do-plots2
; new generation is determined. With a probability 'replace' agents are replaced by the winner of a competition. Two agents are randomly drawn and the best agent is chosen. The child agent has a small variation in the traits due to mutations
ask turtles [
ifelse random-float 1.0 < replace [
set agentA one-of turtles
set agentB one-of turtles
if [payoff] of agentA > [payoff] of agentB [
set alpha [alphaparent] of agentA
set beta [betaparent] of agentA
set w [wparent] of agentA
set symbols [symbolsparent] of agentA
]
if [payoff] of agentB > [payoff] of agentA [
set alpha [alphaparent] of agentB
set beta [betaparent] of agentB
set w [wparent] of agentB
set symbols [symbolsparent] of agentB
]
if [payoff] of agentA = [payoff] of agentB [
ifelse random-float 1.0 < 0.5 [
set alpha [alphaparent] of agentA
set beta [betaparent] of agentA
set w [wparent] of agentA
set symbols [symbolsparent] of agentA
][
set alpha [alphaparent] of agentB
set beta [betaparent] of agentB
set w [wparent] of agentB
set symbols [symbolsparent] of agentB
]
]
; mutations
set alpha alpha + mutrate-alpha * random-normal 0 1
if alpha < 0 [set alpha 0]
if alpha > 1 [set alpha 1]
set beta beta + mutrate-beta * random-normal 0 1
if beta < 0 [set beta 0]
if beta > alpha [set beta alpha]
set tellerS 0
while [tellerS <= nrsymbols]
[
set w replace-item tellerS w (item tellerS w + mutrate-w * random-normal 0 1)
set tellerS tellerS + 1
]
set tellerS 1
while [tellerS <= nrsymbols]
[
if random-float 1.0 < mutrate-s
[
ifelse item tellerS symbols = 0 [set symbols replace-item tellerS symbols 1][set symbols replace-item tellerS symbols 0]
]
set tellerS tellerS + 1
]
][
set alpha alphaparent
set beta betaparent
set w wparent
set symbols symbolsparent
]
]
ask turtles [
set payoff 0
set nrgames 0
set notdrawn? true
]
end
to do-plots
let averagealpha 0
let averagebeta 0
let averagepayoff 0
ask turtles [set averagealpha averagealpha + alpha]
set-current-plot "alpha"
plot averagealpha / nragents
ask turtles [set averagebeta averagebeta + beta]
set-current-plot "beta"
plot averagebeta / nragents
set-current-plot "fraction"
set-current-plot-pen "CC"
plot nrCC / gamespg
set-current-plot-pen "DD"
plot nrDD / gamespg
set-current-plot-pen "CD"
plot nrCD / gamespg
set-current-plot-pen "Exit"
plot nrExit / gamespg
if ticks > 500 [
set avgnrExit avgnrExit + 0.001 * nrExit
set avgnrCC avgnrCC + 0.001 * nrCC
set avgnrDD avgnrDD + 0.001 * nrDD
set avgnrCD avgnrCD + 0.001 * nrCD
set avgalpha avgalpha + 0.001 * averagealpha
set avgbeta avgbeta + 0.001 * averagebeta
set avgpayoff avgpayoff + 0.001 * averagepayoff
]
end
to do-plots2
let averagepayoff 0
ask turtles [set averagepayoff averagepayoff + payoff]
set-current-plot "payoff"
plot averagepayoff / nragents
if ticks > 500 [
set avgpayoff avgpayoff + 0.001 * averagepayoff
]
end
@#$#@#$#@
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alpha
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"" ""
PENS
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PLOT
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beta
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true
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PLOT
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payoff
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"" ""
PENS
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PLOT
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fraction
NIL
NIL
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true
true
"" ""
PENS
"CC" 1.0 0 -16777216 true "" ""
"CD" 1.0 0 -13345367 true "" ""
"DD" 1.0 0 -2674135 true "" ""
"Exit" 1.0 0 -10899396 true "" ""
@#$#@#$#@
This is a Netlogo implementation of the model described in Janssen, M.A. (2008), Evolution of Cooperation in a One-Shot Prisonerïż½s Dilemma Based on Recognition of Trustworthy and Untrustworthy Agents, Journal of Economic Behavior and Organization 65: 458-471
The original model was implemented in 2002 in Java. Janssen (2008) includes one error in the table of default parameter values. In the original Java model I used absolute values for alpha and beta between 0 and 4. In the paper I scaled it to values between 0 and 1, relative to the difference between the payoff of S and T. I forgot to adjust the mutation rates of alpha and beta from 0.1 to 0.025.
The results of Janssen (2008) are replicated with this Netlogo version.
The replication is performed by Marco A. Janssen, Arizona State University, March 2008.
Copyright (C) 2008 M.A. Janssen
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see .
@#$#@#$#@
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@#$#@#$#@
NetLogo 5.0.2
@#$#@#$#@
@#$#@#$#@
@#$#@#$#@
setup
go
avgnrExit
avgnrCC
avgnrDD
avgnrCD
avgalpha
avgbeta
avgpayoff
@#$#@#$#@
@#$#@#$#@
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@#$#@#$#@
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@#$#@#$#@
PK ·İMLp
¤ codemeta.jsonPK ·İMLĥe~ôX ôX ¤, code/truststranger.nlogoPK VZ