Flocking is a common demonstration of emergence and emergent behaviour, invented in 1987 by Craig Reynolds with his simulation program, Boids. It is a simulation of simple agents which are allowed to move, with basic rules governing their movement. The result is alike to a flock of birds, a school of fish, or a swarm of insects.

Basic flocking is controlled by three simple rules:

1. Separation - avoid crowding neighbours
2. Alignment - steer towards average heading of neighbours
3. Cohesion - steer towards average position of neighbours

With these three simple rules, the flock moves in an extremely realistic way, creating complex motion and interaction that would be extremely hard to create otherwise.

Flocking is a common technology in screensavers, and has found its use in animation. Flocking has been used in many films. Tim Burton's Batman Returns (1992) featured flocking penguins, and Disney's The Lion King (1994) included a wildebeest stampede.

Lee Spector, Jon Klein, Chris Perry and Mark Feinstein studied the emergence of collective behavior in evolutionary computation systems. In their paper Emergence of Collective Behavior in Evolving Populations of Flying Agents they describe such systems in detail.

External links

• Craig Reynolds' Boids page
• NetLogo, a free software for multi-agent modeling, simulation, and the like, including a flocking simulation.