Definition
Emotional contagion is a psychological phenomenon in which you unconsciously mimic another person's facial expressions, voice, way of speaking, and gestures, and end up feeling something similar to what they feel. As we talk and connect with others, we naturally soak up not only their joy and energy but also negative feelings like anxiety, sadness, and irritation.
You Copy the Face Next to You Without Realizing
Maybe a friend walked up to you with a big smile, and the corners of your mouth lifted before you could think. On the other hand, sitting across from someone who is furious can make your heart pound and your body tense up. Just by seeing someone's emotional state, we feel its energy right away.
In experiments, when people are shown photos of smiling or frowning faces, their own facial muscles move slightly in the same direction in under a second. Some researchers point to mirror neurons, first found in monkeys, as a basis for this. But how big a role they play in human emotional contagion is still debated.
There is also an explanation that when your facial muscles move like the other person's, that movement feeds back and affects your own emotions. This is called the facial feedback hypothesis, and how strong the effect is varies from study to study.
So through unconscious imitation, people read each other's feelings fast. The brain does this on its own, with no special effort, which makes it hard to notice yourself taking on the mood of the person beside you.
To Be a Little More Precise
Emotional contagion is a bit different from deep caring or reasoned empathy. There is no step-by-step thinking like "That friend must be so sad because of this and that." In a flash, in under a second, the feeling spreads through an unconscious bodily reaction.
Think back to when humans lived in the wild in prehistoric times, and the reason becomes easy to see. When a fierce beast suddenly burst out of the bushes, and a companion's face filled with fear, it would already be too late if you stopped to wonder, "Why is that person making that face?"
The moment you saw a companion's fear, your own heart had to race and your own fear had to kick in, so everyone could flee without delay. That is why there is an evolutionary explanation that emotional contagion helped a group notice danger quickly and stick together, which gave it a survival advantage.
The same principle still works today. Tens of thousands of fans getting fired up together in a stadium, or laughter rippling through a concert hall, is often explained by emotional contagion.
You Can Catch It Just by Reading Words on a Screen
Emotional contagion doesn't only happen when you're face to face in the same room. If you read angry posts or sharp comments on social media or in online communities for a long time, you may find your own mind getting heavy and edgy before you know it.
Our brains quickly pick up emotional cues from the words, context, and tone in text and video on a screen. When you keep being exposed to information that is thick with one particular emotion, you can get tinted by it without noticing, and you may even start using the same sharp language online.
On the other hand, a warm, kind post or a funny video can lift your mood a lot. A large Facebook experiment (2014) also found a tendency for the emotions in posts to carry over into what readers wrote, though the effect on each individual was very small. But with so many users, even a small effect can add up and spread widely.
That is why some researchers think the information and relationships you are exposed to for long stretches can shape your mood that day. If you feel weighed down after reading something full of negative emotion for a long time, emotional contagion may have played a part.
Common misconceptions
Emotional contagion only happens to people who are weak-minded or emotional.
It's a natural phenomenon that everyone experiences to some degree, without realizing it. How easily it spreads does differ from person to person.
Where you meet it
You walk into a meeting room, and just from your boss's stiff expression, the whole team's mood freezes in an instant.
When a friend is crying in sorrow, your eyes well up before you've even heard the whole story.
In one sentence
It is the brain's natural reaction of unconsciously copying other people's expressions and moods, and feeling their emotions as if they were your own.