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New Insights into Crowd Behavior

Do humans behave differently when they are part of a crowd than they do when they are at home by themselves? There have been theories about this over the years, but now a new study, not by a psychologist or sociologist, but by a physicist, has shed new light on this phenomenon.

According to a study published in the journal Science, hydrodynamic theory can be used to explain the collective, fluid-like behavior of human crowds, which can then predict this behavior. The pioneering study shows how being in a crowd influences people to behave as a crowd and overrides the norms of interaction that occur on an individual level.

“Dynamic Response and Hydrodynamics of Polarized Crowds,” was co-authored by Nicolas Bain and Dennis Bartolo of the Laboratoire de Physique in Lyon, France. Bain, a young Ph.D. student in Physics went to his supervisor, Bartolo, with the idea for the paper and did the study under the supervision of Bartolo. They focus on studying human crowds from an “active matter” physicist’s point of view.

To do the study, Bain and Bartolo studied crowds of marathon runners. They set up cameras high above the crowds so they could film the flow of thousands of marathon runners being sectioned off into different corrals at the starting line of three of the world’s largest marathons in Chicago, Paris, and Atlanta. They focused on the entire crowd as a single unit and applied hydrodynamic theory to collective human movement.
The authors note: “We use tens of thousands of road-race participants in starting corrals to elucidate the flowing behavior of polarized crowds by probing its response to boundary motion. Building on these observations, we lay out a hydrodynamic theory of polarized crowds and demonstrate its predictive power.”

Humans are not inclined to think that they don’t have free will or that their behavior or thinking is influenced by outside forces. Indeed, movies like The Invasion of the Body Snatchers, in which an alien force takes over people’s minds and causes them to behave as automatons, have become a genre of horror film that appears to be singularly offensive to people. The very idea of an outside force taking over our minds sometimes brings about a cold sweat.

And yet this study advances, in a scientific way, the notion that humans, just as swarms of birds or herds of cattle, obey collective laws and behave according to those collective laws when they are part of a group. This theory of the hydrodynamics of polarized crowd behavior has larger implications when one considers historic examples of human behavior not only in crowds but also in groups. Throughout history one can find examples of episodes of group behavior in which individual judgment and reasoning ability fell to the wayside.

While the authors of this study concentrate on marathon racing, studying how crowds of runners obey physical laws as they gather and proceed in their group, I believe their research can be used to understand mass behavior in general.

Mass movements also obey laws. One law might be called the law of authority. This law might be stated thusly: If an authority gives permission for an individual to perform an act which had previous been viewed by the individual as evil, the individual will perform this act. This law was discovered by Stanley Milgram in his famous Obedience to Authority study in the late 1950s. Milgram was interested in studying this topic because he, along with most of the world, was still reeling after the discovery of the Nazi torture and extermination of Jews during World War II.

Milgram’s study had subjects sit in front of a device that had levers for them to push, which allowed them to administer (so they were told) various doses of electric shock going as high as 450 volts to learners in the experiment who gave wrong answers. (The learners were actually actors and did not really receive electric shocks.). Milgram found that all participants in the experiment were willing to administer electric shocks, and 65 percent of them were willing to administer what they thought was 450 volts. Hence the performed an act that they would never have done when left to their own resources and moral code. They did so because an authority told them it was all right to do it.

The United States occasionally sends soldiers overseas to kill people. Theses soldiers willingly kill people because the American government says it is OK to kill people. Other countries do likewise. Throughout history various governments, cultures, cults, religious and political movements have engaged in all kinds of practices because the group sanctioned it.

Once individuals join a group, the become part of a group personality. Just as a herd takes on its own personality and will run down any animal or person in its way, who a human mob will run amok without a trace of guilt. This is just part of what happens in mass movements. There are many other parts that can be explored.

New Insights into Crowd Behavior

Gerald Schoenewolf, Ph.D.

Gerald Schoenewolf, Ph.D. is a licensed psychoanalyst in New York and has been practicing for over 37 years. He works with adults, couples, families, adolescents, and children. He has graduated from three psychotherapy institutes and received a Certificate in Psychoanalysis from the Washington Square Institute in 1981. He has been an Adjunct Assistant Professor of psychology at the Borough of Manhattan Community College since 2002 and has authored thirteen books on psychotherapy and psychoanalysis as well as four novels and a book of poems and drawings. More recently he wrote 20 screenplays (winning four first-place awards at festivals) and produced and directed two feature films.

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APA Reference
Schoenewolf, G. (2019). New Insights into Crowd Behavior. Psych Central. Retrieved on September 30, 2020, from


Last updated: 13 Jan 2019
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