The real power comes when turtles interact with each other.
How Turtles “See” Other Turtles Nearby¶
Find neighbors within a distance:
ask turtles [
let nearby-turtles other turtles in-radius 3
if any? nearby-turtles [
; Do something with nearby turtles
]
]Find the closest turtle:
ask turtles [
let closest min-one-of other turtles [distance myself]
if closest != nobody [
face closest ; Turn toward closest turtle
]
]Simple Interaction Rules¶
Follow your neighbors:
ask turtles [
let neighbors other turtles in-radius 3
if any? neighbors [
let average-heading mean [heading] of neighbors
set heading average-heading
]
forward 1
]Avoid crowding:
ask turtles [
let too-close other turtles in-radius 1
if any? too-close [
let repel-direction mean [heading] of too-close + 180
set heading repel-direction
]
forward 1
]Collective Behavior from Individual Actions¶
When individual turtles follow simple rules about their neighbors, amazing collective patterns emerge:
- Flocking: Turtles that align with neighbors create flocks
- Segregation: Turtles that prefer similar neighbors create clusters
- Information spread: Turtles that copy neighbors spread information
- Traffic jams: Turtles that slow down when crowded create jams
Activity 3: Color Copying¶
Goal: Turtles change color to match nearby turtles
to setup
clear-all
create-turtles 100 [
setxy random-xcor random-ycor
set color one-of [red green blue]
]
end
to go
ask turtles [
; Look at nearby turtles
let neighbors other turtles in-radius 2
if any? neighbors [
; Find the most common color among neighbors
let red-neighbors neighbors with [color = red]
let green-neighbors neighbors with [color = green]
let blue-neighbors neighbors with [color = blue]
; Change to majority color
if count red-neighbors > count green-neighbors and
count red-neighbors > count blue-neighbors [
set color red
]
if count green-neighbors > count red-neighbors and
count green-neighbors > count blue-neighbors [
set color green
]
if count blue-neighbors > count red-neighbors and
count blue-neighbors > count green-neighbors [
set color blue
]
]
; Move randomly
right random 60 - 30
forward 0.5
]
endRun this model:
- Click “setup” to create mixed-color turtles
- Click “go” repeatedly and watch colors cluster together
- Notice how local copying creates global patterns!