Ever noticed that you feel happy around happy people and sad around sad or depressed people, or even agitated around anxious people?
Research shows that if you spend enough time with people, their emotions will actually rub off on you.
The MNS is a bit like a high-definition camera that observes and records every detail of people's facial expressions, body language, pupil movements and even vocal tones. So if you're hanging out with someone who is happy, and their happiness is written all over their face, so to speak, your MNS will record their displays of happiness but it will also signal the same displays in you.
For instance, we know that happy people tend to smile a lot. In their presence, your MNS will record activity in the two major smile muscles: the ones that pull your lips upwards (zygomaticus major) and the ones that crease the sides of your eyes (orbicularis oculi). They will then signal your own smile muscles so that you will find yourself smiling more. But that's not all that happens.
The MNS also contains emotional areas of the brain. Some of these are signaled, too, helping to mirror, in you, the emotional state of the happy person.
What can we take from this? Well, if you want to be happier, you wouldn't go far wrong by hanging out with happy people.
Depression is just as contagious as happiness. Should we then avoid people who are depressed? I don't think so. We should help people who are depressed. Anyone who has ever been depressed, and I am a past member of that club, wants to feel loved and cared for, not avoided like they have the plague.
My personal experience is that there is little risk of "catching" depression if you are compassionate to their feelings and are aware of emotional contagion. The compassion allows you to sense how the person feels, to empathize and appreciate their pain, so that they feel listened to. Then, after a while, you can try to "infect" them with your positive mood.
You don't need to try to feel positive. Just recognize that your body language and facial expressions reflect mood, so use these as tools to raise the mood of both of you. Lift your shoulders back, breathe deeply and easily and smile if you can. With any luck, their MNS will be able to mirror you and, at least a little, move them closer to your emotional state, offering them some momentary relief from the pain they feel.
Emotional contagion has been with the human species for a very long time. It helped our ancestors understand each other in a time before language, where they could recognize fear, for instance, by having the same feelings induced in them, thus helping them survive potential danger.
It is present in us from birth. One crying infant will set off a wave of crying in a hospital ward. Studies also show that infants and children mirror the facial expressions of the primary caregiver, suggesting that they feel the same emotions, too, or at least their nervous system is reacting to the emotions of the caregiver.
So the answer to the question, "Are your emotions contagious?" is almost certainly yes. Spend time with happy people if you want to feel happier, and help to raise the spirits of people who feel sad. And if you do feel happy, spread some good cheer around you.
That's how I see we can apply this new knowledge.
For general information on mirror neurons, see: M. Iacobani, 'Mirroring People,' Farrar, Straus, and Giroux, New York, 2008
For general information on emotional contagion, see: E. Hatfield, J. T. Cacioppo, and R. L. Rapson, 'Emotional Contagion,' Cambridge University Press, Cambridge, 1994
For more info on emotional contagion and the relative contagiousness of happiness and depression, see David R. Hamilton PhD, 'The Contagious Power of Thinking,' Hay House, London, 2011