The Wisdom of Crowds
Excerpt from the book “The Wisdom of Crowds” by James Surowiecki, one of the most interesting book I’ve ever read.
Imagine that you are French. You are walking along a busy pavement in Paris and another pedestrian is approaching from the opposite direction. A collision will occur unless you each move out of the other’s way. Which way do you step?
The answer is almost certainly to the right. Replay the same scene in many parts of Asia, however, and you would probably move to the left. It is not obvious why. There is no instruction to head in a specific direction (South Korea, where there is a campaign to get people to walk on the right, is an exception). There is no simple correlation with the side of the road on which people drive: Londoners funnel to the right on pavements, for example.
Instead, says Mehdi Moussaid of the Max Planck Institute in Berlin, this is a behaviour brought about by probabilities. If two opposing people guess each other’s intentions correctly, each moving to one side and allowing the other past, then they are likely to choose to move the same way the next time they need to avoid a collision. The probability of a successful manoeuvre increases as more and more people adopt a bias in one direction, until the tendency sticks. Whether it’s right or left does not matter; what does is that it is the unspoken will of the majority.
That is at odds with most people’s idea of being a pedestrian. More than any other way of getting around—such as being crushed into a train or stuck in a traffic jam—walking appears to offer freedom of choice. Reality is more complicated. Whether stepping aside to avoid a collision, following the person in front through a crowd or navigating busy streets, pedestrians are autonomous yet constrained by others. They are both highly mobile and very predictable. “These are particles with a will,” says Dirk Helbing of ETH Zurich, a technology-focused university.
Messrs Helbing and Moussaid are at the cutting edge of a youngish field: understanding and modelling how pedestrians behave. Its purpose is not mere curiosity. Understanding pedestrian flows makes crowd events safer: knowing about the propensity of different nationalities to step in different directions could, for instance, matter to organisers of an event such as a football World Cup, where fans from various countries mingle. The odds of collisions go up if they do not share a reflex to move to one side. In a packed crowd, that could slow down lots of people.
In 1995 Mr Helbing and Peter Molnar, both physicists, came up with a “social force” computer model that used insights from the way that particles in fluids and gases behave to describe pedestrian movement. The model assumed that people are attracted by some things, such as the destination they are heading for, and repelled by others, such as another pedestrian in their path. It proved its worth by predicting several self-organising effects among crowds that are visible in real life.
One is the propensity of dense crowds spontaneously to break into lanes that allow people to move more efficiently in opposing directions. Individuals do not have to negotiate their way through a series of encounters with oncoming people; they can just follow the person in front. That works better than trying to overtake. Research by Mr Moussaid suggests that the effect of one person trying to walk faster than the people around them in a dense crowd is to force an opposing lane of pedestrians to split in two, which has the effect of breaking up the lane next door, and so on. Everyone moves slower as a result.
Up close and personal
Another self-organising behaviour comes when opposing flows of people meet at a single intersection: think of parents trying to shepherd their children into school as other parents, their sprogs already dropped off, try to leave. As people stream through in one direction, the pressure on their side of the intersection drops. That gives those waiting on the other side more opportunity to go through, until pressure on their side is relieved. The result is a series of alternating bursts of traffic through the gates.
This oscillation in flows is clever enough to have got Mr Helbing wondering about its application to cars. Traffic-light systems currently operate on fixed cycles, with lights staying green on the basis of past traffic patterns. If those patterns are not repeated, drivers are left to idle their engines for too long at red signals, raising emissions and tempers. Mr Helbing thinks it is better to have decentralised, local systems, which—like parents at the school gates—can respond to a build-up of traffic and keep the lights on green for longer if need be. City authorities agree: Mr Helbing’s ideas will soon be implemented in Dresden and Zurich.
Trying to capture every element of pedestrian movement in an equation is horribly complex, however. One problem is allowing for cultural biases, such as whether people step to the left or the right, or their willingness to get close to fellow pedestrians. An experiment in 2009 tested the walking speeds of Germans and Indians by getting volunteers in each country to walk in single file around an elliptical, makeshift corridor of ropes and chairs. At low densities the speeds of each nationality are similar; but once the numbers increase, Indians walk faster than Germans. This won’t be news to anyone familiar with Munich and Mumbai, but Indians are just less bothered about bumping into other people.
Another problem with assuming people act like particles is that up to 70% of people in a crowd are actually in groups. That matters, as anyone trying to get past shuffling tourists knows. It also leads to some lovely fine-scale choreography when small groups are squeezed. Observations of pavement crowds in Toulouse in France show that clusters of three and four people naturally organise themselves into concave “V” and “U” shapes, with middle members falling back slightly. If a group of three people cared about moving quickly, they would behave like geese and form a convex “V”, with the middle member slightly in front to forge a path. Instead, they adopt a formation that enables them to keep communicating with each other; talking trumps walking.
Mr Moussaid’s solution to such complexity has been to build a model based less on the analogy between humans and particles and more on cognitive science. Agents in this new model are allowed to “see” what’s in front of them; they then try to carve a free path through the masses to get to their destination. This approach produces the same effects of lane-formation in crowds as the physics-based models, but with some added advantages.
In particular, boffins think it could help make emergency evacuations safer. Simulating evacuations is a big part of what pedestrian modellers do—the King’s Cross underground fire in London in 1987 gave the field one of its starting shoves. One big danger in an emergency is that people will follow the crowd and all herd towards a single exit. That in turn means that the crowd may jam as too many people try to force their way through a single doorway.
The physics-based models do have an answer to this problem of “arching” (so called for the shape of the crowd that builds up around the exit). Their simulations suggest the flow of pedestrians through a narrow doorway can be smoothed by plonking an obstacle such as a pillar just in front of the exit. In theory, that should have the effect of splitting people into more efficient lanes. In practice, however, the idea of putting a barrier in front of an emergency exit is too counter-intuitive for planners to have tried.
The cognitive-science model offers a more palatable option, that of experimenting with the effects of changes in people’s visual fields. Mr Moussaid speculates that adaptable lighting systems, which use darkness to repel people and light to attract them, could be used to direct them in emergencies, for example.
Where the cognitive approach falls down is in the most packed environments. “At low densities, behaviour is cognitive and strategic,” says Mr Moussaid. “At high density, it’s about mass movement and physical pressures.” At a certain point crowds can shift from a controlled flow to a stop-and-go pattern, as people are forced to shorten their stride length and occasionally halt to avoid collisions. This kind of movement can develop into something much more frightening, known as crowd turbulence, when people can no longer keep a space between themselves and others. The physical forces that are imparted from one body to another when that happens are both chaotic and powerful: if someone falls over, others will be unable to avoid them.
Science meets religion
Working out precisely how and when these transitions happen is tough. Bringing a real-life situation under control once a stop-and-go pattern has started is equally hard. So the trick is to ensure that serious crowding is avoided in the first place. From big events such as the London Olympics to the design of new railway stations, engineering firms now routinely simulate the movement of people to try to spot areas where crowding is likely to occur.
A typical project involves using off-the-shelf software programs to identify potential bottlenecks in a particular environment, such as a stadium or a Tube station. These models specify the entry and exit points at a location and then use “routing algorithms” that send people to their destinations. Even a one-off event like the Olympics has plenty of data on pedestrian movement to draw on, from past games to other set-piece gatherings such as, say, city-centre carnivals, which enable some basic assumptions about how people will flow.
Once potential points of congestion are identified, more sophisticated models can then be used to go down to a finer level of detail. This second stage allows planners to change architectural designs for new locations and identify when to intervene in existing ones. “There should be many fewer crowd disasters given what we now know and can simulate,” says Mr Helbing.
The biggest test possible of these tools and techniques is the haj, the annual pilgrimage to Mecca in Saudi Arabia that Muslims are expected to carry out at least once in their lives if they can. With as many as 3m pilgrims making the journey each year, the haj has a long history of crowd stampedes and deaths. Indeed, video footage of a haj stampede is used by lots of modellers to validate their simulations of crowd turbulence.
The Saudi authorities have brought in consultants in recent years, focusing in particular on the layout of the Jamarat Bridge, where pilgrims perform a ritual in which they throw stones at three pillars. By making the crossing one-way, and changing the shape of the pillars so that people can stone them from a number of locations, they have improved the bridge’s safety.
But according to Paul Townsend of Crowd Dynamics, a consultancy that has worked on the pilgrimage, the risks remain significant. He thinks that the use of gates that could be opened and shut would help to manage the flow. Yet the haj presents some very specific difficulties beyond its sheer scale. Part of the problem is not having a clear idea of how many pilgrims will turn up, which makes planning difficult. Another issue is the nature of the crowd.
“Pilgrims on the haj have the attitude that, if I die there it is God’s will,” says Mr Townsend. “There is a willingness to get more and more dense in the space.” Scientists can model many aspects of pedestrian behaviour, but religious fervour is a step too far.
Source: The Economist
“We become what we behold. We shape our tools and then our tools shape us.”
Musician Bobby McFerrin shows a wonderful example of how well people and the crowd quickly and naturally adapt to situations.
Great series of videos from Red Wing Shoes, explaining their passion even for small details such as a stitch, and their pride on making durable and strength shoes.
Source: Red Wing Shoes
“Life is like riding a bicycle. To keep your balance, you must keep moving.”
A Scientific Fable
“But a Watch in the Night”
A Scientific Fable by James C. Rettie
Out beyond our solar system there is a planet called Copernicus. It came into existence some four or five billion years before the birth of our earth. In due course of time it became inhabited by a race of intelligent men.
About 750 million years ago the Copernicans had developed the motion picture machine to a point well in advance of the stage that we have reached. Most of the cameras that we now use in motion picture work are geared to take twenty-four pictures per second on a continuous strip of film. When such film is run through a projector, it throws a series of images on the screen and these change with a rapidity that gives the impression of normal movement. If a motion is too swift for the human eye to see it in detail, it can be captured and artificially slowed down by means of the slow-motion camera. This one is geared to take many more shots per second — ninety-six, or even more than that. When the slow motion film is projected at the normal speed of twenty-four pictures per second, we can see just how the jumping horse goes over the hurdle.
What about motion that is too slow to be seen by the human eye? That problem has been solved by the use of time-lapse camera. In this one, the shutter is geared to take only one shot per second, or one per minute, or even one per hour — depending on the kind of movement that is being photographed. When time-lapse film is projected at the normal speed of twenty-four pictures per second, it is possible to see a bean sprout growing up out of the ground. Time-lapse films are useful in the study of many types of motion too slow to be observed by the unaided, human eye.
The Copernicans, it seems, had time-lapse cameras some 757 million years ago and they also had super-powered telescopes that gave them a clear view of what was happening upon this earth. They decided to make a film record of the life history of earth and to make it on the scale of one picture per year. The photography has been in progress during the last 757 million years.
In the near future, a Copernican interstellar expedition will arrive upon our earth and bring with it a copy of the time-lapse film. Arrangements will be made for showing the entire film in one continuous run. This will begin at midnight of New Year’s Eve and continue day and night without a single stop until midnight of December 31st. The rate of projection will be twenty-four pictures per second. Time on the screen will thus seem to move at the rate of twenty-four years per second; 1440 years per minute; 86,400 years per hour; approximately two million years per day; and sixty two million years per month. The normal life span of individual man will occupy about 3 seconds. The full period of earth history that will be unfolded on the screen (some 757 billion years) will extend from what geologists call the Pre-Cambrian times, up to the present. This will, by no means, cover the full time-span of the earth’s geological history, but it will embrace the period since the advent of living organisms.
During the months of January, February and March, the picture will be desolate and dreary. The shape of the land masses and the oceans will bear little resemblance to those that we know. The violence of geological erosion will be much in evidence. Rains will pour down on the land and promptly go booming down to the seas. There will be no clear streams anywhere except where the rains fall upon hard rock. Everywhere on the steeper ground the stream channels will be filled with boulders hurled down by rushing waters. Raging torrents and dry stream beds will keep alternating in quick succession. High mountains will seem to melt like so much butter in the sun. The shifting of land into the seas, later to be thrust up as new mountains, will be going on at a grand scale.
Early in April there will be some indication of the presence of single-celled living organisms in some of the warmer and sheltered coastal waters. By the end of the month it will be noticed that some of these organisms have become multicellular. A few of them, including the Trilobites, will be encased in hard shells.
Toward the end of May, the first vertebrates will appear, but they will still be aquatic creatures. In June about 60 percent of the land area that we know as North America will be under water. One broad channel will occupy the space where the Rocky Mountains now stand. Great deposits of limestone will be forming under some of the shallower seas. Oil and gas deposits will be in process of formation —also under shallow seas. On land there will be still no sign of vegetation. Erosion will be rampant, tearing loose particles and chunks of rock and grinding them into bays and estuaries.
About the middle of July the first land plants will appear and take up the tremendous job of soil building. Slowly, very slowly, the mat of vegetation will spread, always battling for its life against the power of erosion. Almost foot by foot, the plant life will advance, lacing down with its root structures whatever pulverized rock material it can find. Leaves and stems will be giving added protection against the loss of the soil foothold. The increasing vegetation will pave the way for the land animals that will live upon it.
Early in August the seas will be teeming with fish. This will be what geologists call the Devonian period. Some of the races of these fish will be breathing by means of lung tissue instead of through gill tissues. Before the month is over, some of the lung fish will go ashore and take on a crude lizard-like appearance. Here are the first amphibians.
In early September, the insects will put in their appearance. Some will look like huge dragonflies and will have a wing spread of 24 inches. Large portions of the land masses will now be covered with heavy vegetation that will include the primitive spore-propagating trees. Layer upon layer of this plant growth will build up, later to appear as the coal deposits. About the middle of this month, there will be evidence of the first seed-bearing plants and the first reptiles. Heretofore, the land animals will have been amphibians that could reproduce their kind only by depositing a soft egg mass in quiet waters. The reptiles will be shown to be freed from the aquatic bond because they can reproduce by means of a shelled egg in which the embryo and its nurturing liquids are sealed and thus protected from destructive evaporation. Before September is over, the first dinosaurs will be seen — creatures destined to dominate the animal realm for about 140 million years, and then to disappear.
In October, there will be a series of mountain uplifts along what is now the eastern coast of the United States. A creature with feathered limbs - half bird and half reptile in appearance, will take itself into the air. Some small and rather unpretentious animals will be seen to bring forth their young in a form that is a miniature replica of the parents and to feed these young on milk secreted by mammary glands in the female parent. The emergence of this mammalian form of animal life will be recognized as one of the great events in geologic time. October will also witness the high water mark of the dinosaurs — creatures ranging in size from that of the modern goat to monsters like Brontosaurus that weighed some 40 tons. Most of them will be placid vegetarians, but a few will be hideous looking carnivores, like Allosaurus and Tyrannosaurus. Some of the herbivorous dinosaurs will be clad in bony armor for protection against their flesh-eating comrades.
November will bring pictures of the sea extending from the Gulf of Mexico to the Arctic in space now occupied by the Rocky Mountains. A few of the reptiles will take to the air on bat-like wings. One of these, called the Pteranodon, will have a wingspread of 15 feet. There will be a rapid development if the modern flowering plants, modern trees, and modern insects. The dinosaurs will disappear. Toward the end of the month, there will be a tremendous disturbance in which the Rocky Mountains will rise out of the sea to assume a dominating place in the North American landscape.
As the picture runs into December it will show the mammals in command of the animal life. Seed-bearing trees and grasses will have covered most of the land with a heavy mantle of vegetation. Only the areas newly thrust up from the sea will be barren. Most of the streams will be crystal clear. The turmoil if geologic erosion will be confined to localized areas. About December 25 will begin the cutting of the Grand Canyon by the Colorado River. Grinding down layer after layer of sedimentary strata, this stream will finally expose deposits laid down in Pre-Cambrian times. Thus in the walls of that canyon will appear geological formations dating from recent times to the period when the earth had no living organisms upon it.
The picture will run on through the latter days of December and even up to its final day with still no sign of mankind. The spectators will become alarmed in the fear that man has somehow been left out. But not so; sometime about noon on December 31 (one million years ago) will appear a stooped, massive creature of man-like proportions. This will be Pithecanthropus, the Java ape man. For tools and weapons he will have nothing but crude stone and wooden clubs. His children will live a precarious existence threatened on one side by hostile animals and on the other by tremendous climactic changes. Ice sheets — in places 4000 feet deep — will form in the northern parts of North America and Eurasia. Four times this glacial ice will push southward to cover half the continents. With each advance the plant and animal life will be swept under or pushed southward. With each recession of ice, life will struggle to re-establish itself in the wake of the retreating glaciers. The woolly mammoth, the musk ox and the caribou will all fight to maintain themselves near the ice-line. Sometimes they will be caught and put into cold storage — skin, flesh, blood, bones and all.
The picture will run on through supper time with still very little evidence of man’s presence on the earth. It will be about 11 o’clock when Neanderthal man appears. Another half hour will go by before the appearance of Cro-Magnon man, living in caves and painting crude animal pictures on the walls of his dwelling. Fifteen minutes more will bring Neolithic man, knowing how to chip stone and thus produce sharp cutting edges for spears and tools. In a few minutes more it will appear that man has domesticated the dog, the sheep and, possibly, other animals. He will then begin the use of milk. He will also learn the arts of basket weaving, and the making of pottery and dugout canoes.
The dawn of civilization will not come until about five or six minutes before the end of the picture. The story of Egyptians, the Babylonians, the Greeks and the Romans will unroll during the fourth, the third and second minute before the end. At 58 minutes and 43 seconds past 11:00 pm (just 1 minute and 17 seconds before the end) will come the beginning of the Christian era. Columbus will discover the new world 20 seconds before the end. The Declaration of Independence will be signed just 7 seconds before the final curtain comes down.
In those few, fleeting moments of geologic time will be the story of all that has happened since we became a nation. And what a story it will be! A human swarm will sweep across the face of the continent and take it away from the [Native Americans]. They will change it far more radically than it has ever been changed before in a comparable time. The great virgin forests will be seen going down before axe and fire. The soil, covered for eons by its protective mantle of trees and grasses, will be laid bare to the ravages of water and wind erosion. Streams that had been flowing clear will, once again, take up a load of silt and push it toward the seas. Humus and mineral salts, both vital elements of productive soil, will be seen to vanish at a terrifying rate. The railroads and highways and cities that will spring up may divert attention, but they cannot cover up the blight of man’s recent activities.
In great sections of Asia, it will be seen that man must utilize cow dung and every scrap of available straw or grass for fuel to cook his food. The forests that once provided wood for this purpose will be gone without a trace. The use of these agricultural wastes for fuel, in place of returning them to the land, will be leading to increasing soil impoverishment. Here and there will be seen a dust storm darkening the landscape over an area thousands of miles across.
Man-creatures will be shown counting their wealth in terms of bits of printed paper representing other bits of a scarce but comparatively useless yellow metal that is kept buried in strong vaults. Meanwhile, the soil, the only real wealth that can keep mankind alive on the face of this earth is savagely being cut loose from its ancient moorings and washed into the seven seas.
We have just arrived upon this earth. How long will we stay?
James C[ardno] Rettie (1904-1969) was an economist with the United States Forest Service at the time this essay was written in 1948. He later served as economic advisor from 1963 to 1969 to Secretary of the Interior Stewart L. Udall. The essay has appeared in numerous anthologies and books about the skills of writing since it was originally published in The Land, Vol. VII, No. 3, Fall 1948 (New York: Harper & Brothers), including:
The cover story in the March 1951 issue of Coronet Magazine under the title “The Most Amazing Movie Ever Made” and it was used in A Psychiatrist’s World: The Selected Papers of Karl Menninger, M.D., Edited by Bernard M. Hall, M.D., (New York: The Viking Press, 1959); and it is also in A Writer=s Reader, Third Ed., by Donald Hall and D.L. Emblem, (Boston: Little Brown and Co., 1979); and The Bedford Reader, edited by X.J. Kennedy and Dorothy M. Kennedy (New York: St. Martin=s Press, 1982); in Purpose and Pattern: A Rhetoric Reader, edited by Elizabeth Penfield, University of New Orleans (Glenview, Ill., Scott Foresman & Co., 1982); in Patterns of Exposition 10 edited by Randall E. Decker with assistance of Robert A Schwegler, 4th Ed. (Boston: Little Brown & Co, 1986; , and
Also: The Norton Reader: An Anthology of Expository Prose, Sixth Ed., Arthur M. Eastman, et al (New York: W.W. Norton & Company); The Riverside Reader, Third Ed., by Joseph F. Trimmer and Maxine Hairston (Boston: Houghton Mifflin Co., 1990); Prentiss Hall Literature Gold, Paramount Edition, compiled by The Master Teacher Editorial Board (Englewood Cliffs, N.J.: Prentiss Hall, 1994); and it is in Of Bunsen Burners, Bones, and Belles Lettres: Classic Essays across the Curriculum by James D. Lester (Chicago: NTC Publishing Group, 1996); and
It is reprinted as the Introduction to The Nature of Alaska: An Introduction to Familiar Plants and Animals and Natural Attractions by James Kavanagh (Blaine, Wash.: Waterford Press, 1997); and 75 Readings Plus, Fourth Ed., by Santi V. Buscemi and Charlotte Smith (Boston: McGraw-Hill, 1998); and in three “The Nature of . . .” books by James Kavanagh for Arizona, California, and Florida, all having the same title as the one covering the State of Alaska cited above (Guildford, Conn.: Globe Pequot Press, 2006.)
“Here’s to the Crazy Ones”
Steve Jobs narrates the first Think different commercial “Here’s to the Crazy Ones”. It never aired. Richard Dreyfuss did the voiceover for the original spot that aired. However Steve’s is much better 1997
Inspired by how whirlpools and hurricanes works in nature, inventor Jay Harmon uses the spiral shape to stir 10 million gallons of water with a couple of light bulbs worth of power, keeping in this way hundreds of water storage tanks clean without the use of chlorine or other chemicals.