Starlings, Humans And "Emergent Order"


  • Noah Strycker describes the swarming behavior of starlings in his enjoyable book The Thing with Feathers: The Surprising Lives of Birds and What They Reveal About Being Human.
  • Starling flocks produce intricate flight patterns that seem coordinated, but in fact result from each individual starling following a small set of simple rules.
  • This kind of “emergent order” also occurs in human behavior, such as the operation of free economic markets in which individual agents pursue their own self interest.

A Murmuration Of Starlings

Large flocks (“murmurations”) of starlings produce intricate flight patterns, first all moving in one direction and then suddenly moving in another. It is tempting to think there must be a leader or set of leaders as one observes in the “V formations” that geese produce. But Ed Young’s excellent description of swarming behavior in Wired explains that is not the case:

“If a falcon attacks, all the starlings dodge almost instantaneously, even those on the far side of the flock that haven’t seen the threat. How can this be? Italian physicist Andrea Cavagna discovered their secret by filming thousands of starlings from a chilly museum rooftop with three cameras and using a computer to reconstruct the birds’ movements in three dimensions. In most systems where information gets transferred from individual to individual, the quality of that information degrades, gets corrupted—like in a game of telephone. But Cavagna found that the starlings’ movements are united in a “scale-free” way. If one turns, they all turn. If one speeds up, they all speed up. The rules are simple—do what your half-dozen closest neighbors do without hitting them, essentially. But because the quality of the information the birds perceive about one another decays far more slowly than expected, the perceptions of any individual starling extend to the edges of the murmuration and the entire flock moves.”

A starling by simply minimizing the separation distance between itself and its seven nearest neighbors transmits information observed by the entire flock almost instantaneously.

Greg Reynolds wanted to produce realistic animations of bird flocks in 1986 and found he could do so with a small set of rules that each "individual" follows independently as described in the Wikipedia article on his "Boids" code:

  • separation: steer to avoid crowding local flockmates
  • alignment: steer towards the average heading of local flockmates
  • cohesion: steer to move toward the average position (center of mass) of local flockmates

More complex rules can be added, such as obstacle avoidance and goal seeking.
The basic model has been extended in several different ways since Reynolds proposed it. For instance, Delgado-Mata et al.[3] extended the basic model to incorporate the effects of fear.”

It turns out “intelligent” swarming occurs in many species such as sheep, locusts, honey bees and fish such as shiners. Shiner schools find safety as a group simply because individuals swim more slowly in darker water so the whole school seems to pivot towards darker, more protected areas.

Human Analogies

There are also lots of examples of human behavior in which seemingly complex information is transmitted by simply observing the behavior of others. For example it is easier to observe if your neighbors are putting out their garbage cans, or moving their parked cars from one side of the street to the other than remembering the rules for garbage day or parking yourself.

Terms applied to this kind of “individual behavior” that seems to produce complex coordinated behavior include “emergent order” and “spontaneous order.” An enjoyable hour can be spent listening to Russ Roberts’ podcast “Econtalk” in which he talks with John McWhorter about how even the English language is a good example of “emergent order.”

Turning to economics, “emergent order” was posited by Adam Smith in 1776 in his  Wealth of Nations:

"Every individual necessarily labors to render the annual revenue of the society as great as he can ... He intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention ... By pursuing his own interests, he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good."

While “emergent order” can produce efficient economic outcomes as suggested by Adam Smith, investing booms and busts also arise from individuals being influenced by the greed or fear of their “nearest neighbors.” Defenders of laissez-faire economics would not dispute that, but would also argue that “emergent order” produces better outcomes than those that arise from “central planning.”

In practice, however, no country pursues strictly laissez-faire policies. Like geese, humans seem to have an instinctive belief in the usefulness of “leaders.”


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