Social Contagion: How Others Secretly Control Your Behavior

Ron Riggio
3 min readSep 26, 2022


Key points

  • Social contagion is the spread of emotions or behaviors from one individual to another, sometimes without awareness.
  • Social contagion processes become problematic when they lead to spates of aggressive or self-injurious behaviors.
  • An example of social contagion is the 1962 June Bug, when workers developed all the same psychologically-induced symptoms.

Co-authored by Clara Riggio

In June of 1962, dozens of workers in a textile factory came down with the same physical symptoms-rashes, numbness in the hands and feet, and episodes of nausea. It was initially believed that the factory had been infested with some sort of toxic insect that had bitten the workers. This became known as the “June Bug Epidemic.”

What happened? It was determined that this was a form of mass hysteria or social contagion. Some workers developed these psychologically-induced symptoms, and others developed the same complaints as the “disease” spread from worker to worker.

Social contagion is the subtle and sometimes unwitting spread of emotions or behaviors from one individual to others.

Emotional contagion is the spread of emotions through crowds and is the reason why a movie seems funnier if we are in a crowded theater as opposed to watching it alone-our mood is influenced by those laughing around us. The same process would cause a stampeding wave of fear if someone were to suddenly yell “Fire!” in the crowded theater.

A study by Friedman and Riggio (1981) found that emotionally expressive individuals-persons who displayed high instances of nonverbal cues of emotion (primarily facial expressions)-were able to “infect” the emotions/moods of others in the room without any verbal interaction. Subsequent research found that certain individuals are more prone to emotional contagion processes (Doherty, 1997).

Behavioral contagion is the process by which others’ behaviors are replicated. This explains fads such as the Rubik’s Cube craze of the 1970s and the ALS Ice Bucket Challenge-where individuals filmed themselves dumping a bucket of ice water on their heads in a campaign to promote awareness of amyotrophic lateral sclerosis (ALS) disease.

Where social contagion processes become problematic is when there is a spread among people of harmful behaviors. Think about how a crowd of protesters might suddenly erupt into violence, as in the January 6th, 2021, attack on the U.S. Capitol. Social contagion may also be blamed for waves of self-injurious behaviors, such as extreme diets, self-cutting, copycat shootings, and even suicide.

One categorization of contagion suggests these categories:

Hysterical Contagion. Such as the June Bug incident or the epidemics of dancing manias in the Middle Ages, as people would spontaneously dance until exhaustion. One such episode, tarantism, was believed to have been caused by tarantula bites.

Deliberate Self-Harm. Such as “epidemics” of self-cutting, eating disorders, and suicides.

Contagions of Aggression. Riots, the recent spate of “smash and grab” robberies, and the like.

Rule Violation Contagions. An example of this is when people observe other drivers speeding on the highway, and they start to speed themselves, or it might explain instances of “doping” that occur in waves among some professional athletes.

Consumer Behavior Contagions. This is responsible for the buying crazes that occur, such as the run on toilet paper that occurred at the beginning of the Covid-19 pandemic, the Beanie Babies craze of the 1990s, and the hula hoops craze of the 1950s.

Financial Contagions. Self-explanatory. This explains the Great Depression and the run on banks that occurred in 1929, as well as economic recessions and financial crises that occur every few years.

So, the next time you find yourself engaging in unexpected behavior, you might look around and try to figure out if you have been a victim of social contagion.

Originally published at



Ron Riggio

Professor of Leadership and Organizational Psychology at Claremont McKenna College; Author; Consultant