Exploring Complex Systems through Games and Computer Models Santa Fe Institute – Project GUTS

What is a complex system? Complex difficult-to-understand or difficult to predict System A group of interacting, interrelated, or interdependent parts forming a whole. So a “Complex System” is collections of simple units or agents interacting in a system. Large-scale behaviors of the system are difficult to understand or difficult to predict and may change, evolve, or adapt. (Also called Complex Adaptive Systems)

Climate change Loss of biodiversity Pollution Civil violence Spread of disease All of these issues are studied as “complex systems” using computer models. Traffic jams Forest fire evacuation These local problems can also be studied as complex systems: Some problems we face

Scientists recreate complex systems in a "virtual world" on a computer where they are able to run many experiments without impacting the real world. How do scientists study complex systems?

The Computational Science Process StarLogo is a tool used to create a Computational Model Begin here

Creating Computer Models with StarLogo TNG Create agents and environment Give agents and environment simple rules to follow No sophisticated mathematics or programming required Explore the behavior of complex systems The Predator, Prey, and Grass Model

Modeling and Computational Science A model is a representation of the interaction of real-world objects in a complex system. The goal is to gain an understanding of how the model’s results relate to real-world phenomena. Random factors built into the model and variables changed by the user cause different results to be generated when the model is run repeatedly.

* Model Classification * Idea Models Idea Models e.g. Model of Predator and Prey e.g. Model of Predator and Prey Minimal Models for Systems Minimal Models for Systems e.g. Model of Wolves and Caribou e.g. Model of Wolves and Caribou Systems Models Systems Models e.g. Model of every Wolf and Caribou in 5 square mile section of Yellowstone e.g. Model of every Wolf and Caribou in 5 square mile section of Yellowstone *This classification scheme was proposed by J. Roughgarden. Increasing complexity and detail Decreasing generality and applicability

Why wouldn’t you want to run these experiments in real-life?

What are Characteristics of Complex Adaptive Systems?

L eaderless (aka decentralized) Characteristics of Complex Adaptive Systems

A classic example Birds Flocking

A classic example flocking - Craig Reynolds Separation: steer to avoid crowding local flockmates Alignment: steer towards the average heading of local flockmates Cohesion: steer to move toward the average position of local flockmates

E mergent patterns develop from the simple interactions of agents Characteristics of Complex Adaptive Systems

A classic example Termites Termites model

N on-linear The sum of the parts is not equal to the whole. Characteristics of Complex Adaptive Systems

In Mathematics N on-linear means: f(a+b)  f(a) + f(b) Ex.) the exponential function is non-linear. f(2 + 3)  f(2) + f(3) f(2 + 3)  f(2) + f(3) f(5)  f(2) + f(3) f(5)  f(2) + f(3) 25   *Non-linear systems are systems that cannot be mathematically described as the sum of their components.

S elf-organization The system organizes itself. Characteristics of Complex Adaptive Systems

A classic example Schelling Segregation Model Developed by Thomas C. Schelling (Micromotives and Macrobehavior, 1978).

1. L eaderless there is no leader (boids) 2. E mergent patterns develop from the simple interactions of agents. (termites) 3. N on-linear The sum of the parts does not equal the whole. 4. S elf-organization The system organizes itself 4 Characteristics of Complex Adaptive Systems

Complex System or just Complicated?

Some examples of Complex Adaptive Systems Global climate patterns Global climate patterns A termite mound A termite mound Highway traffic patterns Highway traffic patterns The spread of a disease in a population The spread of a disease in a population The evolution of ideas in a society The evolution of ideas in a society A food web in an ecosystem A food web in an ecosystem

The End