Imagine, if you will, a flock of birds. There are thousands of them scattered in a field resting, until, suddenly in one glorious motion they lift off at once. The entire flock rises into the sky, flips back and forth, as if it were a single organism with a single purpose, and comes to rest at once on some power lines. It’s an amazing sight, especially with larger flocks of birds, and it’s an example of emergent behavior.
Flocking birds do not deliberately coordinate their actions. The do not plan out ahead of time who goes where or in what direction they will go, yet they regularly and spontaneously pull off complex areal maneuvers that daring human pilots would only attempt after years of practice. The trick is that each bird follows the bird next to it. If that bird starts off in a new direction, then the first one follows. They continually maintain a safe distance from each other, each going with the flow so that they all end up going in the same direction at once. When a few birds start off in a different direction, the others follow. This is called flocking (or herding when sheep do it,) and it’s the result of simple behaviors on the part of individuals in a group resulting in more complex behaviors on the part of the whole of the group. This is emergent behavior.
Emergent behavior is present throughout nature. Ants are another good example. Ants build enormous nests, cooperatively raise food for colonies with millions of individuals, ford rivers using their own bodies as bridge parts, and fight elaborate wars with other colonies and even other species. Some species of ants are even capable of migrating an entire colony at once. Yet no one ant plans out the actions of the colony. No group of ants either. In fact, ants are not clever enough to understand the entirety of the colonies endeavors anyway. Instead, instinct guides the ant. One ant discovers food and leaves a scent trail all the way back to the nest; other ants follow the scent trail and soon enough there is an entire column of ants rapidly disassembling a piece of food and transporting it back to the nest. The harvest is so orderly and cooperative that the ants don’t even have traffic jams.
One interesting thing about emergent behavior is that the behavior is often more complex that what would have been possible through a planned approach. The rules that an individual member of a flock follow are simple compared to a hypothetical attempt to plan the location of every single bird as part of a large movement. In such systems you not only have to consider the location, speed, direction, and acceleration of each individual bird, but you have to consider the same for each bird, in relation to every single other bird as well. When you have problems like that, solutions don’t “scale,” that is, the solution stops working as the problem size grows larger. In computer science, the complexity of a problem is often expressed in terms of something called “Big-O” notation, or for example: O(n^2). “n” being the number of birds, this means that the complexity of this problem is the number of birds squared, because each bird needs to be considered in terms of each of the other birds. So when there are only five birds, we need only consider 25 relationships, but with there are 50 birds, 2500 relationships need to be handled. So, as the number of birds grows, the difficulty of planning their movements grows at an unmanageable rate.
Yet, if we use the emergent behavior approach, each bird need only consider those immediately around it, shrinking the problem to at most O(n), or more often to O(k), where n is the number of birds in a flock and k is the number of birds able to be near each other bird. So if there are at most 10 birds near each other bird, the problem will always 10 in size no matter how many birds their are. In this approach, the problem scales trivially, which shows the power of emergent behavior.
My favorite example of emergent behavior is that of the human economy. The task of successfully predicting and fulfilling the needs and wants of billions of humans every day is a monumental one. Not only do completely unpredictable events, natural disasters and wars complicate the task, but people’s wants and needs change and interact in completely unpredictable ways. As people move into an area for example, the number of automobiles sold there will increase, but after a certain threshold, this will change because increasing traffic and population density makes cars less useful and more of a hassle. As certain needs are met, other needs rear their heads and become prominent. Planning, producing, and distributing the worlds goods is a nearly impossible task, yet it mostly gets done consistently year after year.
This principle of individual action leading to results which are beneficial to the whole is something on which our species depends for survival. If it did not exist, humanity would not have been able to form the economies on which early civilizations and their learning and governance depended. In all of human history, there has never been a body capable of planning, or even enforcing a plan for a whole civilization.
Historically, attempts at centrally planned economies have generally been failures. Soviet Russia had to abandon it’s original collectivism for the New Economic Policy for example. But, remove the task of arranging society from a select few and give it to the multitude and the problem suddenly becomes tractable. Individuals acting only in response to their own circumstances inadvertently contribute to the feeding and clothing of the planet. Markets are an intrinsic part of human nature that arise whenever a large enough civilization forms and they remain in place regardless of the official economic system put in place by any government. Even North Korea has an underground market which staves of starvation for many in that economy.
Markets are an amazing principle that underpins much of human behavior. The are an excellent example of emergent behavior and it’s a shame that they are sometimes under-appreciated.