Positive Contagion

And how you can use it to improve productivity

Jonathan Adrian, MD
5 min readFeb 27, 2020


In the year 1518, a major plague stirred up the French region of Alsace. It all started when a young woman, Frau Troffea, started dancing fervently in a street in rural Strasbourg. Inexplicably, people started to dance along with her, only they did it for days on end and they couldn’t stop.

Within one week, 34 other people had joined, and within one month, this number had rose to over 400 people. At this point, people started dying from exhaustion, heart attacks, and strokes. One source even indicated that for a short period of time within the month, this plague killed 15 people in a single day.

I did not make this up. The story above was quoted from an event called the dancing plague of 1518, and is now thought to be one of the earliest documentations of mass hysteria. Sociologist Robert Bartholomew, in his peculiar little book titled Little Green Men, Meowing Nuns and Head-Hunting Panics, defines it as “a phenomenon that transmits collective illusions of threats, whether real or imaginary, through a population in society as a result of rumours and fear.”

This event of mania began to spread all over Europe, and people started coming up with theories as to what may have caused this event. Among the most popular theories at that time were sacrilegious demonic possessions and overheated blood. Much later in the 20th century, scientists suggest that those afflicted may have consumed bread made of rye flour that was contaminated with ergot, which is a type of fungus.

American medical historian John Waller then began looking into psychogenic disorders as the culprit behind this outbreak, which were events that took place under circumstances of extreme stress and generally take form based on local cultures and tradition.

In the case of the dancing plague of 1518, John Waller cited a series of famines and the presence of debilitating diseases such as smallpox and syphilis as the overwhelming stressors affecting residents of Strasbourg.

He further maintained that there was a local belief that those who failed to appease St. Vitus, the patron saint of epileptics and dancers, would be cursed by being forced to dance.

In other words, an incessant sense of fear and anxiety disseminated upon the citizens of Strasbourg in 1518, transmitted through the vector of relentless dancing. This was emotional contagion at the dawn of human knowledge in the field of psychology.

Many centuries later, we are still seeing sporadic reports of mass hysteria consuming small populations in different parts of the earth. Last year, this event resurfaced in 58 girls in Kenya who were isolated with an unknown disease that manifested as high-pitch coughs, sneezing, and fever.

It was later found that out of the 58 students, only 2 tested positive for a viral infection. It was for a common strain of rhinovirus that is responsible for causing the common cold. After performing mental assessments on the students, the Kenyan Ministry of Health later concluded that this “mysterious disease” was a case of mass hysteria.

But emotional contagion does not always lead to the negative extremes. Whereas profound emotional and physical stress may lead to events of hysteria, studies have shown that positive triggers, such as laughter and joy can be contagious as well.

Can you remember the last time you stumbled upon a funny meme or video while scrolling through your social media feed? You probably laughed along, let a little smile sneak up on your face, and perhaps even shared it with a friend to get them to laugh as well.

In just the same way, a video of a human being inappropriately harassing an animal can make us feel sad, or even angry. Emotions, both positive and negative, actually spread among people, just like 1518’s deadly dance.

A study by Elaine Hatfield and her colleagues in 1994 demonstrated that emotional contagion most often occurs at a significantly less conscious level, based on automatic processes and physiological responses. And while older studies focused on contagion between two people, I notice that they are just as equally prevalent in group settings.

Sigal Barsade, who is a Management Professor at Wharton, ran an experiment in 2014 where she divided business school students into small groups for a management class exercise. Each student had to play the role of a department head advocating for an employee to get a merit-based increase, but at the same time, had to play with a limited pot of funds, so they had to balance between getting the most for their own candidate with maximising the overall benefit to the company.

Each group was seeded with a confederate trained to convey one of four different mood conditions: cheerful enthusiasm, serene warmth, hostile irritability, and depressed sluggishness.

The findings demonstrated a significant effect of emotional contagion. Groups in which the confederate had ‘spread’ positive emotions similarly reported an increase in positive mood. But the emotional contagion did not stop there, and Barsade observed that these groups also displayed more cooperation and less interpersonal conflict.

In terms of performance of the task at hand, Barsade noticed that the group that was seeded by the ‘positive’ confederate did significantly better than groups that were affected by negative emotions from the variable group.

“When the students were asked why they allocated the funds the way they did, and why they thought their group performed the way it did, they pointed to factors such as their own negotiating acumen, or the qualities of the “candidates” they had been assigned,” says Barsade. “They had no inkling that their behaviour and decisions, and that of their group, had been directed by the displayed emotion of the confederate.”

This can be particularly useful in an office setting, especially if you’re overseeing management of a team, but individuals can also commission benefits from this phenomenon. The information you come across with on a daily basis, the people you surround yourself with, and the environment that you’re in play a vital role in determining how you feel and act in every day life.

By being mindful about the information you consume and the social circle of friends you surround yourself with, you are psychologically-speaking, hacking your way into finding your best form.

Can you recall that one time you received a flowery text from your crush and that boosted your mood for the entire day? Or been a part of the pay-it-forward chain? Or became extremely motivated to pay back your debts after successfully clearing up your first one?

Positive contagion is the puppeteer behind these seemingly addicting emotional transfers. Kindness begets kindness. Evil begets evil. Emotions are the currency of mood setting. The trading medium you use, be it positive or negative, lies fully within your control.

We’ve probably seen social media posters about one’s work attitude being “catchy”. Barsade’s research shows that it’s even more catching than one might think — and in fact has profound consequences for a company’s productive output. But armed with an awareness of emotional contagion, managers and individuals have the potential to create more productive teams, companies, and entrepreneurial ecosystems.



Jonathan Adrian, MD

Doctor, writer, photographer, and part-time social media strategist.