評論
打印
Science and Technolgy
科技
Social science
社會科學
Wisdom about crowds
關于群體的思考
To model the behaviour of humans en masse, treat them as people, not molecules
在為人類的全體活動建立模型時，要將他們看作是"人"，而不是"分子"。
THE behaviour of crowds is sometimes unpredictable and occasionally deadly, but there is good reason to believe it is governed by simple rules. Presumably, like molecules in a liquid, people in a crowd all behave in more or less the same way. Capture those similarities in a model and it should be possible to predict how a crowd will behave.
群體的行動有時候是不可知的，偶然致使的，不過有充分的理由相信，這種行為符合簡單的規律。簡單說來，這就像液體中的分子，在群體中的人的行動大致是一樣的。在一個模型中捕獲這些相似性可以對于一個群體的行動進行預測。
Existing models of crowd behaviour do just that. They treat moving masses of humanity as though they were fluids. This works, up to a point. But it often fails to predict the changes that happen as a crowd's density increases and its movement becomes chaotic. That is why Mehdi Moussaid of Paul Sabatier University, in Toulouse, and his colleagues have made a radical innovation. Instead of treating the individual human beings in a crowd as if they were molecules, they have treated them as if they were human beings. They have, in other words, given them volition. Of course, the objective of someone in a moving crowd is usually fairly simple-to get somewhere and then stay there. But it is an objective, nevertheless.
現有的大眾行動模型就可以做到這一點。這些模型將變化的人類群體當作是液體。在某種程度（或者條件）下，這個模型非常有效。不過當涉及到群體的密度增加，運行變得混亂時，對于預測發生的變化往往不能奏效。這就是保爾?薩巴蒂大學（Paul Sabatier University，在圖盧茲）的邁赫迪?穆賽德（Mehdi Moussaid）和他的同事已經進行突破性創新的原因。與以往的理論中將群體看作是分子不同，他們將群體看作是"人"。換句話說，就是考慮到了"人的意志"。當然了，在一個活動的群體中的客觀存在的一些人通常比較簡單：到哪里，就待在那。即使這樣，它還是一個客觀存在的事物。
As they describe in the Proceedings of the National Academy of Sciences, Dr Moussaid and his team built a computer model in which, initially, every virtual person in the crowd followed two rules. The first was that each attempted to chart as straight as possible a path to his destination, such as an exit or the end of a corridor, while avoiding obstacles, including other pedestrians. Second, each adjusted his speed, depending on his distance from such obstacles.
就像他們在《美國國家科學院學報》中所描述的那樣，穆賽德博士和他的團隊建立了一個計算機模型，在這個模型里，起先，每個虛擬的在群體中的人都服從兩個規律。第一，當避開包括其他行人在內的障礙時，每個人都試圖盡量以直線的的路線到達目的地，就像一個出口或一個走廊的盡頭。第二，每個人都會調整自己的速度，這個依賴于與障礙物的距離。
These two rules were enough to reproduce in the model the sorts of behaviour seen in real crowds, such as the tendency people have to sort themselves spontaneously into separate lanes of traffic moving in opposite directions and the stop-and-go motion that occurs as crowds become more dense. When Dr Moussaid really put the pressure on, however, by increasing the density of the virtual crowd, the model did not show the extreme turbulence seen in real crowds-the sudden crushes and chaotic changes in direction.
這兩個規則在真實的群體中的各種行為上已經得到了足夠的驗證，例如，在公路上，人們通常會趨向于同時將自己朝相反的方向移動，這種停停走走的行為，讓本來發生的擁擠更加擁擠。當穆賽德博士確實增加壓力時——通過增加虛擬人群的密度，在真實的人群中，這個模型并沒有顯示出的騷亂——驟然的碾壓和方向變化的混亂。
These happen because in extremely dense crowds there is so much shoving and jostling that people's movements are no longer entirely under their own control. In other words, they actually do start behaving like molecules in a fluid, bouncing off one another at random. To mimic that behaviour, Dr Moussaid added a third rule, which made members of his crowd more molecule-like when they were at very close quarters-a lack of volition that will be familiar to anyone who has been in a tight jam of humanity.
因為在極其密集的人群里，有很多人推搡和擁擠，人們自身的行動并不受自己的控制，因此會發生混亂。換句話說，這個時候，他們就像液體中的分子一樣，被任意地反彈。為了模擬這種行為，穆賽德博士又增加了第三條規律，即當群體中的成員之間非常接近的時候，他們就像分子一樣，此時群體中的成員是缺乏意志的，對那些處于擁擠人群里的人來說，這種感覺深有體會。
With this third rule added, the model accurately reproduced the dynamics of dense crowds as well as those of sparser ones. At first, a crowd flows smoothly. Then, as more people are added, it begins to show stop-and-go patterns and sometimes extreme crushing. Finally, it displays the sort of turbulence that can lead to disaster. On one run, for example, the model showed precisely the pattern seen in a video of a catastrophe in Mecca in 2006, when 346 pilgrims there on the haj were crushed to death.
有了這第三條規律的補充，無論在動態密集的人群里還是在稀疏的人群里，這種模型都會精確在得到再現。最初，人群流動順暢。接著，更多的人加入，整個人群開始變成時走時停的模型，有時候還變得極度擁擠。最后，人群變得混亂，并能導致災難。例如，在2006年麥加的朝覲的災難上，根據視頻的顯示內容，這種模型得到了精確的顯示，當時有346名朝圣者在混亂中被踩踏至死。
The practical upshot of all this, Dr Moussaid hopes, will be improvements in the design of public spaces where crowds are likely to gather, especially in the location of evacuation routes. That is an outcome greatly to be desired. And it was made possible by remembering that people are not molecules.
穆賽德博士希望，所以有這種真實的結果會對有助于改善公共場所的設計，尤其是對于疏散通道位置的考慮，在這種場合下，有可能聚集大量的人。這是一個非常值得注意的結果。一定要牢記，人，不是分子。
