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Tuesday, 27 November 2007

From ants to collective sentinence

Americans spend a 3.7 billion hours a year in congested traffic. But you will never see ants stuck in gridlock.

Army ants, which Dr. Couzin has spent much time observing in Panama, are particularly good at moving in swarms. If they have to travel over a depression in the ground, they erect bridges so that they can proceed as quickly as possible.

“They build the bridges with their living bodies,” said Dr. Couzin, a mathematical biologist at Princeton University and the University of Oxford. “They build them up if they’re required, and they dissolve if they’re not being used.”

The reason may be that the ants have had a lot more time to adapt to living in big groups. “We haven’t evolved in the societies we currently live in,” Dr. Couzin said.

By studying army ants — as well as birds, fish, locusts and other swarming animals — Dr. Couzin and his colleagues are starting to discover simple rules that allow swarms to work so well. Those rules allow thousands of relatively simple animals to form a collective brain able to make decisions and move like a single organism.

Dr. Couzin has discovered some of those rules in the ways that locusts begin to form their devastating swarms. The insects typically crawl around on their own, but sometimes young locusts come together in huge bands that march across the land, devouring everything in their path.

The scientists found that when the density of locusts rose beyond a threshold, the insects suddenly began to move together. Each locust always tried to align its own movements with any neighbor. When the locusts were widely spaced, however, this rule did not have much effect on them. Only when they had enough neighbors did they spontaneously form huge bands.

Swarms, regardless of the forces that bring them together, have a remarkable ability to act like a collective mind. A swarm navigates as a unit, making decisions about where to go and how to escape predators together.

“There’s a swarm intelligence,” Dr. Couzin said. “You can see how people thought there was some sort of telekinesis involved.”

What makes this collective decision-making all the more puzzling is that each individual can behave only based on its own experience.

Dr. Couzin and his colleagues have built a model of the flow of information through swarms. Each individual has to balance two instincts: to stay with the group and to move in a desired direction. The scientists found that just a few leaders can guide a swarm effectively. They do not even need to send any special signals to the animals around them. They create a bias in the swarm’s movement that steers it in a particular direction.

Dr. Couzin and his colleagues have been finding support for this model in real groups of animals. They have even found support in studies on mediocre swarmers — humans.

As Dr. Couzin’s model predicted, the human swarm made a quick, unconscious decision about which way to go. People tended to follow the largest group of leaders, even if it contained only

The rules of the swarm may also apply to the cells inside our bodies. Dr. Couzin is working with cancer biologists to discover the rules by which cancer cells work together to build tumors or migrate through tissues. Even brain cells may follow the same rules for collective behavior seen in locusts or fish.one additional person.

“How does your brain take this information and come to a collective decision about what you’re seeing?” Dr. Couzin said. The answer, he suspects, may lie in our inner swarm.
(source-NY Times)

My comment: I'm completely overwhelmed by this article. It makes so much sense to me on so much levels, I'm just beginning to comprehend it little by little. I'm gonna post something on it in After The Pink Goat so make sure you check it. It's gonna be big, you can be sure on this! I just want to urge you to read the whole article in NY Times as it's very very interesting and has so much in it, I barely managed to paste some key moments. Just a little comment on it: What really impressed me is that no matter of the motives behind being in a swarm, the swarm acts like a different entity. And that you need very simply mathematical model to describe that behaviour or to simulate it. Isn't it magnificent we can't optimize the traffic with the brute force of complex models but we can with very simple ones? I think it is!

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