Much of human behavior is a product of social influences resulting from both types of conformity. Consider some examples:

Employees are far more likely to file suit if members of the same workgroup have also done so.19

Teenage girls who see that other teenagers are having children are more likely to become pregnant themselves.20

Broadcasters mimic one another, producing otherwise inexplicable fads in programming.21

The level of violent crime is greatly influenced by the perceived behavior of others in the community.22

Members of Congress pay close attention to the cues set by their colleagues, often following the consensus position or those whom they trust, especially on issues outside of their own areas of expertise.23

Whether and how people plan for retirement is much affected by the behavior of others in their workgroup.24

The academic effort of college students in New England is affected by their peers, so much so that random assignments of first-year students to dormitories have significant consequences.25

In deciding whether to adopt new technologies, including high-yielding methods to produce rice, farmers are greatly influenced by the decisions of their peers.26

Lower courts follow one another, especially in highly technical areas, and hence judicial mistakes may be self-perpetuating.27

By emphasizing informational and reputational influences, I attempt to provide a unified account of three distinct phenomena: conformity, social cascades, and group polarization. Indeed, one of my central purposes is to show that these three phenomena result from the same two influences. The idea of conformity is straightforward. Social cascades occur over time. They begin as one or a few people initially engage in certain acts-participating in a political


protest, buying a distinctive pair of shoes, converting to a new religion, investing in particular stocks, seeking a certain kind of education. Others then follow them, thinking that these initial movers are probably right or wanting to gain social approval. Still others, influenced by the decisions of their increasingly numerous predecessors, follow too. Advertisers dream about creating cascade effects, which are common for restaurants, toys, books, movies, and clothing. But cascades also benefit, or harm, political candidates, job applicants, medical treatments, colleges, financial opportunities, and even points of view. Sometimes doctors follow one another to the great detriment of patients. If a number of states, or even nations, enact the same law within a short period, cascades are likely to be involved. When cascades occur, the key problem is that the followers are failing to disclose or to rely on their private information. Because society does not receive that information, serious trouble and indeed catastrophe can result.

Group polarization occurs when group members, engaged in deliberation with one another, end up taking a more extreme position in line with their predeliberation tendencies. The jury study mentioned above is a simple example: High levels of outrage grow even higher as a result of deliberation, while low levels of outrage fall. Because outrage is a strong motivating force, the jury study helps explain many forms of extremism. Individuals who are outraged become more outraged still as a result of speaking with one another. The phenomenon occurs on talk radio and on the Internet, among sports fans, within political parties, even within nations. When like-minded judges go to extremes, the same phenomenon is involved. So too when people in a company or a government end up taking a risk that most of those involved would be unwilling to take on their own. Political correctness, in all its forms, develops through group polarization. And when group polarization occurs, it is usually because of simultaneous informational and reputational cascades. Violence is sometimes produced in this way.