1

Computational Social Psychology

​

Week 2: Creating your very first model

Jiin Jung, Ph.D.

Lehigh University

jiin.jung@lehigh.edu

Life (1958)

“La plume de ma tante

est sur le bureau de mon oncle”

Objectives

• When you learn a new language, you start with super simple, often idiotic, not very useful, phrases.

​

• The same principle can be applied to learning a new programming language.

​

• Let’s make our ‘la plume de ma tante’ model - a super simple, quite idiotic, not very useful, model.

Open the code tab in NetLogo

Types the code below

Create “command buttons” in Interface

Create “command buttons” in Interface

“step” is go but for just one tick

Let’s run the model

• All agents show exactly same actions.
• They move forward by 1 and turn right by 10.

​

​

​

​

​

​

* If you can track agents actions, use “pen-down”

Let’s bring some randomness�This makes agents heterogeneous

Now agents randomly pick an integer between 0 to 9,

and turn right by that number

Let’s run again

• Each agents shows different trajectories of actions.

You want to parameterize a population

• What would you do if you want to have a different number for an initial population?

Create an interface element

to input a parameter value

You want to parameterize a population

• What would you do if you want to have a different number for an initial population?

Replace 10 with a parameter label, “population”

Let’s run the model with 60 turtles

Let’s get agents interact with other agents�– This brings ‘sociality’ to agents

1. Agents find friends within their reach.
• Agents have imperfect local knowledge.

​

1. If there is any other agents within their reach, they become more social.

​

Programming “social” agents

Agents find friend(s) at each iteration

Each turtle has its own friend(s).

🡪 This is called a turtle variable

Make turtles social – make friends

Let’s make agents' sociality visible to us

• Agents size represents their sociality.

​

Programming “social” agents

If an agent has any friend(s), the agent gets bigger

Let’s run the model with 60 turtles

Program ‘Friends bring more friends’

• More social agents come to have larger reaches when they find friends.

​

Let’s program “social agents become more social”

Sociality

• Sociality increases very very fast.

​

Let’s plot how fast sociality increases?

• Calculate the mean of turtles’ size

Let’s plot how fast sociality increases?

• Calculate the mean of turtles’ size

Global variables

• Global variables are outside of turtle’s view as opposed to turtle variables which are accessible only to self-agent.
• You can make a global variables accessible to all agents if necessary.

Create a plot in interface tab

Plotting the frequency distribution of sociality

Notice the patterns of sociality increases

“La plume de ma tante” model

Resources

​

NetLogo User Manual. Version 7.0.0. (2025)

• https://docs.netlogo.org/

​

​

​

​