Imagine you’re having a regular day, feeling neither happy nor sad.

Then you meet up with a friend who is buzzing with excitement about something great that’s just happened to them.

Without even trying, you start to feel a little lighter, a little happier. What if I told you this isn’t just a coincidence, but a well-documented scientific phenomenon? And the further effects are quite astonishing.

Scientists James Fowler and Nicholas Christakis studied data from thousands of people in a large social network and found something incredible: happiness is contagious.

For example, if someone you are friends with becomes happier for some reason, then there’s a fairly decent chance that you will also become happier over the next few weeks or months.

They even put some numbers on it. If it was an immediate social contact who became happier, the chances of you becoming happier were 15%. But this was an average of social contacts in general, people you know and interact with from time to time. If the person who became happier was someone you considered a friend, then the chances of you becoming happier was 25%.

And if this friend was a close mutual friend, and who lived within a mile of you, the chances of you becoming happier if they became happier increased to 63%.

How is this even possible?

Well, there’s two main factors. One is emotional contagion and the other is behavioral contagion. And they both fit under the umbrella of social contagion.

Emotional contagion

Emotional contagion is the phenomena where we ‘catch’ the emotions of people we spend time with, just as you can catch a cold from someone you interact with. It’s facilitated by a network of brain cells known as the Mirror Neuron System (MNS).

When someone you’re with smiles, your MNS picks up their facial muscle movements and automatically triggers the same ones in you.

That’s what the ‘mirror’ bit means. It’s why you tend to smile when someone smiles, frown when someone frowns, even tense when you see someone looking fearful. 

But this is only half of it. At the same time, your MNS pings the emotional regions of your brain that are consistent with the smile, so you not only smile but you also feel a bit better.

In this way, if they’re smiling because they feel happy about something, within seconds you find yourself smiling and feeling happier too.

Behavioral contagion

With behavioral contagion, we become happier when someone’s behaviour around us changes. So if your friend becomes happier and starts behaving differently, their happier behaviour has a knock-on effect on you. 

For example, maybe they want to go out more, share more coffees and conversation, go to the cinema. As you go along, these experiences result in you becoming happier too.

It can also be caused by imitation. For example, say your happier friend tidies their garden and decorates their home because of how they’re feeling, you may well get the urge to do the same yourself, and reap the rewards of satisfaction at the extra cleanliness and colour in your life.

Contagious happiness tends to work through both these pathways.

And it depends on the quality of relationship. It’s much stronger if you are close friends, but less so if a friendship is one-sided. For example, if someone thinks of you as a friend but you don’t see them in the same way, then there’s only a 12% chance of their happiness impacting you.

The ripple effect

Where things get really interesting is that happiness can spread much further than from just one person to another. Happiness actually spreads up to what’s known as 3 degrees of separation.

This means that if you become happier, you will increase the likelihood of your friends becoming happier (1-degree), your friends’ friends (2-degrees), and your friends’ friends’ friends (3-degrees). And most likely you have never met, nor will ever meet, most of the people in this latter group. Yet your change in happiness affects them.

That’s amazing! To put some numbers to it, starting with the 15% average figure I mentioned above, which is the likelihood of your contacts (in general) at 1-degree of separation from you becoming happier if you become happier, Fowler and Christakis found that people at 2-degrees of separation from you stand a 10% chance of becoming happier because you have become happier.

And that’s the fascinating bit: because you became happier. Not for some other seemingly random reason. But because you became happier.

And then it extends farther. People at three degrees of separation from you – remember, these are your friends’ friends’ friends – have a 6% chance of becoming happier because you became happier.

Let’s put this into perspective. Say you have ten friends and each of them have ten friends, so that’s 100 people at two degrees of separation from you, and each of these people also have ten friends, that’s 1,000 people at three degrees of separation from you.

So roughly 60 of these people will find themselves feeling a bit happier over the next few weeks or months because you have become happier, either through emotional or behavioral contagion.

If you ever doubted how deeply connected we all are, just let those number sink in for a second.

So the next time you do something that lifts your mood – a walk in nature, a heartfelt conversation, an act of kindness – remember that the benefits may extend far beyond yourself. Your happiness might just be the spark that ignites a wave of joy for people you’ll never even meet.

Resources

The main reference for the 3-degrees of separation research is: J. H. Fowler and N. A. Christakis (2008), ‘Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study’, British Medical Journal, 337, a2338. Link to study.

If you want to read more about contagious emotions and experiences (happiness, depression, fear, loneliness, weight changes, divorce), how it works, how it happens in the workplace, even how playing violent computer games or watching violent movies can affect us, see my book, ‘The Contagious Power of Thinking’. Ref: David R Hamilton PhD, ‘The Contagious Power of Thinking’. Link to book on Amazon UK Link to Amazon US Amazon Australia Amazon Canada (it is available in some other countries too).

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