INTRODUCTION WHEN IN DOUBT, TURN TO THE EXPERTS
Not long ago Southwest Airlines was wrestling with a difficult question: Should it abandon its long-standing policy of open seating on planes? Of all the major airlines, Southwest was the only one that let passengers choose where to sit once they got on board. The airline had done it that way for more than thirty-four years, and it took pride in being an industry maverick. The company’s independent attitude had helped make it one of the largest airlines in the world. Southwest, remember, was the first carrier to encourage flight attendants to tell jokes in the air.
Lately, though, some customers, especially business travelers, had complained that the free-for-all to get on a Southwest plane was no fun. To obtain a good seat, travelers had to arrive at the airport hours before their flight to secure a place at the head of the line, or remember to print out a boarding document the day before from the company’s online reservation system. Some said the process made them feel more like cattle than customers, which, in the competitive airline business, was a problem. So Southwest put the issue on the table; if assigned seating would make people happier, the company was willing to consider it.
The question turned out to be more complicated than it seemed. For one thing, no one knew how assigned seating would affect the amount of time it would take for Southwest to board everybody. If assigned seating made the process faster, then switching made sense, of course. But if it slowed things down, it wouldn’t help. Boarding speed depended, in part, on which pattern was used. Should the company start in the back of the plane and work forward? Should it start in the front and move to the back? What about boarding window seats first, then middle seats, and then, finally, aisle seats? How about alternating among various zones? Each strategy offered advantages and disadvantages, and each required a different amount of time. Given such variables, how was the airline supposed to make a decision?
To a Southwest analyst named Doug Lawson, the answer seemed obvious: the best way to determine whether assigned seating would be faster was to create a computer simulation of passengers boarding a plane, and then try out one pattern after the other. Other airlines had done more or less the same thing over the years. But Lawson’s plan had a difference—it was based on the behavior of ants.
“Ants were a good fit for this study, because we had all these individuals pouring into a tight space, interacting with one another,” he says. “Every individual had a task to do—in this case, obtain a seat—while dealing with all the others doing the same thing. In a way, it was a typical biological problem.”
Like real ants, Lawson’s digital ones followed a few simple rules to guide their behavior. “Each ant was allowed to go down the jet ramp and wander onto the plane. If we were simulating open seating in that run, each ant had its own idea of a good place to sit, based on actual passenger data, and it would look over the situation and say, well, I see that seat is open. I’m going to try to get over to that one.” If the path was clear, then the ant moved down the aisle to the appropriate row and took its seat. If the path was blocked by other ants, it either waited a few seconds, or asked them to move aside. (Lawson had to add the waiting rule after a few raucous simulations. “We had all these ants trying to get in through the galley, and they were pushing and shoving and bouncing off each other,” he says. “They were creating chaos on the plane, so we had to tone some of them down.”)
As soon as all the ants were seated, the simulation was finished, and its elapsed time could be compared with those from other runs. Since Southwest flies only Boeing 737s, the physical constraints of the problem were always the same, which made it easier to calibrate Lawson’s simulations with data from actual boardings. In addition, Southwest staged a full day of experiments using employees on a real plane to ground-truth the results. What Lawson determined from all this, after repeating his simulations for every feasible pattern, was that open seating was relatively fast, but that assigned seating, under certain circumstances, could be faster. The difference, though, was only a minute or two—not enough, by itself, to abandon Southwest’s long-standing tradition.
“We have a lot of loyal customers who just like walking onto the plane and sitting with whomever they want to,” Lawson observes. “They saw that as part of our brand, and they didn’t want the brand changed at all.”
So instead of dumping open seating, the airline took another close look at the way passengers were lined up at the gate. If the real problem was that people didn’t like competing for a spot in line, Southwest figured, then why not assign them a spot when they checked in, so they wouldn’t have to worry about it later? Boarding would still be first-come, first-served, but passengers’ places in line would be held as soon as they checked in, whether in person or online. That way, passengers wouldn’t have to show up hours ahead of time and hold their places, and when they got on the plane they could still sit anywhere they wanted, “as long as they didn’t sit on top of somebody else,” Lawson says. Southwest adopted this new system in late 2007.
Why was an ant-based simulation a good idea for Southwest? What do ants and airlines have in common? The answer has to do with the remarkable phenomenon I call a smart swarm. Evolved over millions of years, a smart swarm might be a colony of ants in the desert that has figured out exactly how many workers to assign to various jobs each morning, despite an unpredictable environment. It might be a hive of honeybees in the forest that has worked out a foolproof system to choose just the right tree for a new home, despite conflicting opinions among many individuals. It might be a school of thousands of fish in the Caribbean Sea that knows how to coordinate its behavior so precisely that it can change direction in a flash, as if it were a single silvery creature. Or it might be a vast herd of caribou on an epic migration to an Arctic coastal plain, each animal certain of reaching the calving grounds even though most haven’t got a clue about exactly where they’re going. Simply put, a smart swarm is a group of individuals who respond to one another and to their environment in ways that give them the power, as a group, to cope with uncertainty, complexity, and change.
Inspired by the practical way in which an ant colony splits a big problem into thousands of little ones, for example, Lawson set out to tap into the same kind of swarm intelligence with virtual ants he called “cognitive moving objects.” Although his digital insects were highly simplified simulations, they were designed to capture the fundamental cleverness of real ant colonies. “Down here in Texas we have lots of different types of ants,” says Lawson, who works at Southwest’s headquarters in Dallas. “Take the leaf-cutting ants of central Texas. They have the most amazing social structure you could imagine.” Like their tropical cousins in South America, this ant species (Atta texana) employs an assembly line of workers to farm a symbiotic fungus, which the colony eats. At one end of the assembly line, skillful workers cut pieces of leaves from trees or bushes and carry them back to the nest, as biologists Bert Hölldobler and E. O. Wilson describe in their book The Superorganism. Inside the nest, a second group of workers, slightly smaller in size than the first, snips the leaves into tiny pieces and leaves them for the next group. The third group of even smaller workers chews the pieces into pulp and shapes the pulp into pellets. Then a fourth group of still smaller workers plants strands of fungus inside a pile of pellets in the colony’s subterranean garden. Finally, the smallest workers of all lovingly tend the fungi, removing unwanted spores. “That’s how that shop is run,” Wilson says.
With several million workers per nest, a leaf-cutter colony can harvest a half-ton or so of vegetation a year, which gives you some indication of the incredible power that ants acquire by combining and coordinating their efforts. Such abilities, managed through a sophisticated communication system based on chemicals, has enabled ant colonies to raise their behavior as a group to a level far above that of individual ants. Which is why Wilson and Hölldobler describe such colonies as superorganisms. “The modern insect societies,” they write, “have a vast amount to teach us today.”
To some people, this may come as a surprise. How could ants, bees, or termites know something we don’t? How could such insignificant creatures solve complicated problems better than an $11-billion-a-year airline like Southwest? If ants are so smart, why aren’t they