When people herd together, they instinctively behave as other herd animals.
In most animal groups, the crowd is known to act as one unit. Humans, being animals too, adopt the same kind of herd mentality. The group will act differently than each member would behave individually. When acting as one unit, some dangers can easily arise. People lose control of their usual inhibitions. Their “mentality” becomes of the group. If a car is rocked over after a soccer riot, for instance, enthusiasm for the destructive act is greatly increased due to sheer number of people, and a much stronger determination being born by the bolstered group confidence. All of the adrenaline of the group is exaggerated and acted upon.
People are not just destructive when grouped, however. Defensive or protective circles spontaneously form, and against an adversary people are alert and protective. Such as herds of cows, sheep, deer, gazelles, even elephants do, the animals circle around the weak and the young. If you have ever seen collected animals together, you have likely witnessed that all heads and eyes are generally facing outward, in the direction to be patrolled for possible attacks. When humans do this it is known as “circling the wagons,” in reference to how frontier days covered wagons were grouped in a circle for the defense of the unit.
Contagion theory tells us that the crowd causes people to behave as if a contagion has infected all members. Another theory, called Convergence Theory is almost an inversion of this view. Conversion theory says that individual strengths of powerfully influential members converge into the whole crowd acting as one. Whether it is the influence of powerful individuals, or of each member emphasis and multiplied to more than a sum of its parts, Sociologists are fascinated by crowds.
When a group of people come together and are ignited by extreme emotions, especially when they are emotions of rage over perceived injustice, it is not unusual for beating, lynching, destruction of property, and more mayhem to ensue, even though innocent bystanders are not in any way the figure at which the original violence is aimed. Many riots over civil rights erupted in ugly ways where the public servants became the public abusers.
Over the globe we witness crowds go mad with bull running, sports events, political demonstrations, animal killings, religious frenzy, and more. We must also state that hormones, especially male hormones, play a huge part in these kind of rabbles. If is sounds sexist, perhaps it is. Nature is very sexist when it comes to young males being the greatest perpetrator of out of control violence in riots, flag burnings, protests, and so on. This does not in any way say that females never get involved, a classic example of this is the Manson Family murders that killed the idealism of the 1960’s in graphic and disturbing ways. It must also be pointed out that some crowd behavior is often laudable; When Gandhi roused people to stand up with peaceful Ahimsa it gave birth to democracy. Martin Lutheran King led many an exemplary demonstrations, and one may also remember one brave Chinese student standing down an entire column of tanks, for example.
Mass sociogenic illness:
Another mob mentality phenomenon that occurs is that people, even when not physically in a group, begin to behave with hysteria. In western culture the witch burning craze is noted, that many young women nearly starved, or fasted, or joined strict and brutal religious orders is not as well known. When nuns in the 1490's, in France, began to mew like cats, they were punished, and many cats cited as being familiars to Satan were tortured, hung, and burned. Humans have been known to prompt all kinds of fads that led to out of control runs on markets, inflation's that quickly rise beyond containment, investments such as the one over tulip bulbs in the early 1600;s. Europe, or "animal" magnetism over a period between late 1790-1800’s.
In more recent times, the advent of John Lennon's birthday reminds us how real Beatlemania was, Elvis before that, and every new generation launches its own little hysteria, such as the rave, the YouTube phenomonona, and the popularity of things such as Jack Ass, and World of War craft, cyber bullying, too, is a kind of Groupthink mentality that can be destructive. Anonymity allows people the same covert coverage as does being in an out of control crowd.
Lest you think these hysteria are a thing of the past, realize that every “bubble” that grows and bursts such as the tech bubble in 1999, the housing bubble in early 2,000s, and the credit and finance bubble to which we are still paying heavy costs and consequences are all in part due to crowd mentality.