1. Jochen Triesch, UC San Diego, http://cogsci.ucsd.edu/~triesch 1 Emergence A system with simple but strongly interacting parts can often exhibit very intricate and unexpected behavior. To understand the system, it is not sufficient to study the parts in isolation, but they must be studied together. Examples: schooling and flocking cellular automata neural networks with feedback social insects: bees, ants, termites gene networks economies …

2. Jochen Triesch, UC San Diego, http://cogsci.ucsd.edu/~triesch 2 Schooling and Flocking Behavior HerringAnchovie But why do they flock and school?

3. Jochen Triesch, UC San Diego, http://cogsci.ucsd.edu/~triesch 3 Advantage of schooling and flocking Richard Dawkins: The Selfish Gene: A simple strategy for a predator animal is to chase the closest prey animal in its vicinity. This is reasonable because it expends the least amount of effort for the predator. If you have buddies all around you, you are pretty save!

4. Jochen Triesch, UC San Diego, http://cogsci.ucsd.edu/~triesch 4 But how? -- Bird Flocking and Boids Craig Reynolds: a few local rules sufficient to produce flocking. Nice and simple example of emergent property. Each individual follows these (informal) rules: 1. fly towards the centre of mass of neighbors 2. keep small distance away from other objects (including other boids). 3. match velocity with near boids. (bird+android = boid) 1. cohesion2. separation3. alignment

5. Jochen Triesch, UC San Diego, http://cogsci.ucsd.edu/~triesch 5 Boids Pics, Movies, Links Boids Movie Conrads’s Boid Page Reynolds’s Boid Page

6. Jochen Triesch, UC San Diego, http://cogsci.ucsd.edu/~triesch 6 Lessons Learned global order can arise from local interactions complex behavior can result from simple rules flocking, termite mounds, etc. can’t be predicted by just studying behavior of one individual, limits of reductionism