In a recent discussion about emergence I wrote the following (somewhat edited).
Emergence is what happens when components of the emergent entity act in such a way as to bring about the existence and persistence of that entity. For example, when "boids" follow their local flying rules, they create (* implement*) a flock. It's not mysterious. We know how it works. That's all emergence is: coordinated or consistent actions among a number of elements that result in the formation and persistence of some aggregate entity or phenomenon. The "coordination" doesn't have to be top-down. In flocking, for example, there is local (or networked) coordination. The flying rules for on each boid depend on that boid seeing neighboring boids. One can even say that there is some overall coordination: all the boids follow the same rules. ** It's worth pointing out that in biological and social emergent entities, the components may come and go while the entity persists. What emerges is a pattern of activities, not a physical thing. That's one of the reasons people get confused. (And that's why subvenience is not particularly useful in these cases.) But if you just think about emergence as a persistent pattern of activities, that pretty much takes care of it. It's the fact that the pattern persists that matters, not the elements that are acting to produce the pattern. One of the more interesting issues in complex systems is the formation of entities --. that "boid attraction" creates flocks is a simple example. With that in mind, it might be interesting to do some experiments. For example, How dense does a collection of boids have to be for a flock to form? Or more to the point, if the boids are confined to a limited, e.g., toroidal, space, how does their initial density determine the rate at which the flock forms? What about the other parameters such as the distance each individual boid can see (that is, which boids become neighbors) and the velocity at which the boids are moving compared to the "attraction" they have on each other? This is like gravity and asking whether two passing bodies will form an orbiting system or simply affect each other's velocities as they pass and separate. What if the environment included obstacles that the boids had to avoid. Some of those obstacles could presumably break up a flock. So how do flock formation and flock disintegration interact? There might be other disintegration forces such as boids moving a bit more randomly. How do these results relate to similar results in networks such as network formation and connectivity, etc.? Do any "self-organized criticality" effects appear? Does anyone know whether experiments of this sort have been done, and if so, what the results were? Having written this down, these feel like questions that should have been asked a decade ago. But perhaps there might still be something there. Entity formation is an open and important issue. Perhaps experiments of this sort might shed some light on it -- Russ
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