turtles-own [ dialect colour diff ] globals [ donetalking di lang ] ;; lets the user draw geographical barriers to draw-boundaries if mouse-down? [ ask patch mouse-xcor mouse-ycor [ set pcolor black ] ] end to clear-boundaries clear-patches ask patches [ set pcolor white ] end to setup clear-turtles clear-all-plots reset-ticks set-default-shape turtles "face happy" if count patches with [ pcolor = black ] = count patches [ ask patches [ set pcolor white ] ] create-turtles initial-populations [ setxy random-xcor random-ycor move-to patch-here move-to-white find-new-spot set dialect n-values lang-complexity [ random 2 ] determine-colour ] end ;; fill world with turtles to fill-world ask patches [ if ( pcolor = white ) and ( not any? turtles-here ) [ sprout 1 [ set dialect n-values lang-complexity [ random 2 ] determine-colour ] ] ] end ;; sets all turtles to same dialect to homogenise let uni-dialect [ dialect ] of turtle 0 ask turtles with [ who > 0 ] [ set dialect uni-dialect determine-colour ] end to go set donetalking [ ] ask turtles [ move-to-white mutate check-talkstatus migrate expand ] tick if plot-pop? [ update-plot-crowding ] if plot-di? [ if ticks mod plot-step-di = 1 [ update-plot-di ] ] if plot-lang? [ if ticks mod plot-step-lang = 1 [ update-plot-lang ] ] if ticks > 10000 [ stop ] end ;; sets turtle's colour as sum of dialect-values' percentage of spectrum ;; NB same dialect means same colour, but converse not always true to determine-colour set colour ( ( ( reduce [ ?1 + ?2 ] dialect ) / lang-complexity ) * 140 ) set colour ( floor (colour) ) if colour = 140 [ set colour 0 ] set color colour end ;; only white patches are habitable land to move-to-white while [ pcolor != white ] [ move-to one-of ( neighbors with [ pcolor = white ] ) ] end ;; only one population allowed per patch to find-new-spot let k 0 while [ ( k < 5 ) and ( any? other turtles-here ) ] [ rt random 360 ifelse [ pcolor ] of patch-ahead 1 = white [ fd 1 ] [ rt random 360 ] set k ( k + 1 ) ] move-to patch-here if any? other turtles-here [ die ] end ;; leaves home for a new one to migrate let empty-areas ( neighbors with [ not any? turtles-here and pcolor = white ] ) if count empty-areas > 0 [ if random-float 1 < migration-rate [ move-to one-of empty-areas ] ] end ;; expands population into neigbouring area, if area full then new population seeks new home to expand let empty-areas ( neighbors with [ not any? turtles-here and pcolor = white ] ) if count empty-areas > 0 [ if random-float 1 < expansion-rate [ hatch 1 [ move-to one-of empty-areas ] ] ] end ;; dialect randomly mutates on its own to mutate if random-float 1 < mutation-rate [ let mutant ( random lang-complexity ) set dialect replace-item mutant dialect ( 1 - ( item mutant dialect ) ) determine-colour ] end ;; has the turtle communicated on this tick? to check-talkstatus if not member? who donetalking [ check-compatibility ] end ;; does the pair of turtles speak mutually intelligible dialects? to check-compatibility let dialect-a dialect if any? turtles-on neighbors [ ask turtles-on neighbors [ let dialect-b dialect set diff ( map [ abs ( ?1 - ?2 ) ] dialect-a dialect-b ) let totaldiff ( reduce [ ?1 + ?2 ] diff ) if ( ( totaldiff / lang-complexity ) < ( 1 - intelligibility-ratio ) ) and ( totaldiff > 0 ) [ communicate ] ] ] end ;; finds out where the dialects differ, then changes one of those differences to be the same ;; makes a list of who's communicated on this tick to communicate if random-float 1 < borrow-rate [ let posn [ ] let k 0 foreach diff [ if ? = 1 [ set posn lput k posn ] set k ( k + 1 ) ] let mutant one-of posn set dialect replace-item mutant dialect ( 1 - ( item mutant dialect ) ) determine-colour set donetalking lput ( [ who ] of self ) donetalking set donetalking lput ( [ who ] of myself ) donetalking ] end ;; measures diversity of dialects and of languages, then plots these ;; dialect diversity measured as portion of distinct dialects per total population ;; language diversity measured as reciprocal of average number of dialects that are the same language as a given dialect to update-plot-di let all-dialects [ ] ask turtles [ if not member? dialect all-dialects [ set all-dialects lput dialect all-dialects ] ] set di ( ( length all-dialects ) / ( count turtles ) ) set-current-plot "Diversity" set-current-plot-pen "dialects" set-plot-pen-interval plot-step-di plot di end to update-plot-lang let same-langs [ ] ask turtles [ let dialect-a dialect let k 0 ask other turtles [ let dialect-b dialect set diff ( map [ abs ( ?1 - ?2 ) ] dialect-a dialect-b ) let totaldiff ( reduce [ ?1 + ?2 ] diff ) if ( totaldiff / lang-complexity ) < ( 1 - intelligibility-ratio ) [ set k ( k + 1 ) ] ] set same-langs lput k same-langs ] let x ( mean same-langs ) ifelse x < 1 [ set lang 1 ] [ set lang ( 1 / x ) ] set-current-plot "Diversity" set-current-plot-pen "languages" set-plot-pen-interval plot-step-lang plot lang end to update-plot-crowding set-current-plot "Diversity" set-current-plot-pen "crowding" plot ( count turtles / ( count patches with [ pcolor = white ] ) ) end @#$#@#$#@ GRAPHICS-WINDOW 6 10 653 678 16 16 19.30303030303031 1 10 1 1 1 0 1 1 1 -16 16 -16 16 0 0 1 ticks CC-WINDOW 5 730 1414 825 Command Center 0 SLIDER 662 28 834 61 initial-populations initial-populations 1 500 4 1 1 NIL HORIZONTAL SLIDER 1017 10 1189 43 lang-complexity lang-complexity 1 100 50 1 1 NIL HORIZONTAL BUTTON 518 683 581 716 NIL setup NIL 1 T OBSERVER NIL NIL NIL NIL SLIDER 839 10 1011 43 migration-rate migration-rate 0 0.01 0.0030 0.0001 1 NIL HORIZONTAL BUTTON 590 683 653 716 NIL go T 1 T OBSERVER NIL NIL NIL NIL SLIDER 839 47 1011 80 expansion-rate expansion-rate 0 0.02 0.012 0.001 1 NIL HORIZONTAL SLIDER 1194 10 1366 43 mutation-rate mutation-rate 0 1 0.03 0.01 1 NIL HORIZONTAL SLIDER 1017 47 1189 80 intelligibility-ratio intelligibility-ratio 0 1 0.75 0.01 1 NIL HORIZONTAL PLOT 662 86 1405 679 Diversity time NIL 0.0 10.0 0.0 1.0 true true PENS "dialects" 1.0 0 -16777216 true "languages" 1.0 0 -2674135 true "crowding" 1.0 0 -1184463 true SLIDER 1194 47 1366 80 borrow-rate borrow-rate 0 1 0.75 0.01 1 NIL HORIZONTAL SLIDER 1233 683 1405 716 plot-step-lang plot-step-lang 1 500 200 1 1 NIL HORIZONTAL BUTTON 5 683 130 716 NIL draw-boundaries T 1 T OBSERVER NIL NIL NIL NIL BUTTON 141 683 265 716 NIL clear-boundaries NIL 1 T OBSERVER NIL NIL NIL NIL SWITCH 1118 683 1228 716 plot-lang? plot-lang? 0 1 -1000 BUTTON 315 683 412 716 NIL homogenise NIL 1 T OBSERVER NIL NIL NIL NIL BUTTON 417 683 489 716 NIL fill-world NIL 1 T OBSERVER NIL NIL NIL NIL SWITCH 803 683 906 716 plot-di? plot-di? 0 1 -1000 SLIDER 910 683 1082 716 plot-step-di plot-step-di 1 100 25 1 1 NIL HORIZONTAL SWITCH 662 683 770 716 plot-pop? plot-pop? 0 1 -1000 @#$#@#$#@ WHAT IS IT? ----------- This is a model of language evolution, where agents are human populations that possess a dialect. A dialect is modelled here as simply an ordered array of ones and zeros. HOW IT WORKS ------------ Two dialects are considered variants of the same language if they are mutually intelligible. Otherwise they are different languages. HOW TO USE IT ------------- Mutation rate is how fast dialects change on their own. Borrow rate is how fast they are influenced by neighbouring, mutually intelligible dialects. Mutual intelligibility ratio is how similar two dialects must be for one to say they can understand the other. THINGS TO NOTICE ---------------- If two agents have the same dialect, they will be the same colour. However, two agents with the same colour may or may not have the same dialect. Calculating language diversity is somewhat intense computationally and causes the program to stall momentarily. For this reason a switch and slider are provided to allow you to plot this value less often or not at all. THINGS TO TRY ------------- Try drawing boundaries by clicking on that button and then clicking and dragging on the world. You can draw them first and then populate the world, or populate first and then draw accordingly. EXTENDING THE MODEL ------------------- Each agent could take its mutation rate as a random multiple of the global parameter; the dialect could be modelled with numbers between 0 and some number much higher than 1; the dialect could have sub-arrays to account for the faster- and slower-changing parts of itself, and these could also be weighted when determining the mutual intelligibility; and so on... NETLOGO FEATURES ---------------- This model provided some good exercise in working with lists, the NetLogo equivalent of arrays. RELATED MODELS -------------- Genetic Drift - "GenDrift T interact" is similar in many respects CREDITS AND REFERENCES ---------------------- Made by Chuck Cranston for a class taught by Dr Jeff Fletcher at Portland State University, fall 2009. @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 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 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195 240 210 180 210 165 195 Polygon -7500403 true true 135 195 135 240 120 255 105 255 105 285 135 285 165 240 165 195 line true 0 Line -7500403 true 150 0 150 300 line half true 0 Line -7500403 true 150 0 150 150 pentagon false 0 Polygon -7500403 true true 150 15 15 120 60 285 240 285 285 120 person false 0 Circle -7500403 true true 110 5 80 Polygon -7500403 true true 105 90 120 195 90 285 105 300 135 300 150 225 165 300 195 300 210 285 180 195 195 90 Rectangle -7500403 true true 127 79 172 94 Polygon -7500403 true true 195 90 240 150 225 180 165 105 Polygon -7500403 true true 105 90 60 150 75 180 135 105 plant false 0 Rectangle -7500403 true true 135 90 165 300 Polygon -7500403 true true 135 255 90 210 45 195 75 255 135 285 Polygon -7500403 true true 165 255 210 210 255 195 225 255 165 285 Polygon -7500403 true true 135 180 90 135 45 120 75 180 135 210 Polygon -7500403 true true 165 180 165 210 225 180 255 120 210 135 Polygon -7500403 true true 135 105 90 60 45 45 75 105 135 135 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