Contagion is good.  At least, in an emotional sense, in audiences, and most of the time.  As public speakers, we want to infect the audience with excitement, with humor, with pathos – with all the emotions a speech can evoke.  The reason that’s important is that we humans are a communal species, possessing mirror neurons that spread our feelings from one brain to another like a bee colony finding flowers or a susurration of anxiety amongst meerkats sensing danger.  We love the communal moments that we get at sporting events, or concerts, or political rallies, because they allow us to feel connected through passion with our fellow human beings.

For the speaker, to hear a laugh roll across the auditorium, or a collective gasp of surprise, or to simply feel a visceral moment of shared empathy – these are the moments that let us know our message has been received and that, however briefly, we humans can reach across the gulf of individual consciousness and join together as one.

We all know that laughter is contagious because we’ve experienced the difference between watching a comic alone on Netflix, and in an audience live.  We may find the comedian funny on our own, but we’re far less likely to laugh aloud.  Get us together in a group, however, and hear the laughter roll down like a mighty stream.  Yawning, the opposite on the speaker’s spectrum of desirable outcomes, is similarly infectious.

But what else is particularly sharable?  We know that emotions are generally infectious, and the stronger they are, the more so, but what does specific research tell us?

Contrary to the popular understanding, thanks to all the negative media on the subject, happiness is more sharable online than negative emotions.  In person, parents share anxiety most readily with their children, alas, though steps can be taken (and probably should be) to minimize that particular sharing of emotion.  Parents share most emotions with their children, however, so no need to be anxious about anxiety in particular.

In the workplace, you will not be surprised to learn, rudeness is contagious.  If you experience rude behavior, you are likely to expect it to continue, and you are more likely to pass it on to others.  (Insert passive-aggressive sigh here.)

But, probably for the better, risk-taking is also contagious – a phenomenon that has been well-studied in the financial markets.  A sell-off can easily turn into a rout, and the opposite is also true.  And since overall, at least, the U.S. stock market has been up over the last 100 years, it seems that the positive trend is here to stay.

I remember vividly the first Psych course I took in college.  The professor gave us the assignment of walking down the street in the town where the university was located and smiling at everyone we made eye contact with.  We were supposed to keep track of the total number of people we smiled at, and the number who smiled back.  My memory is that it was roughly 50-50, and indeed research from the 90s found a similar ratio.  I wonder what the percentage would be today, in our famously negative era?  Has social media made trolls of us all?  Who will attempt the experiment in some city where pedestrians are back, and the masks are off?

These simple studies demonstrate the contagion of human emotional states.  Understanding the contagion of our feelings is essential for successful public speaking.  How will you bring your audience together in shared emotion?