The British Medical Journal reported today that happiness was infectious.
(James H Fowler, Nicholas A Christakis, 2008, Dynamic spread of happiness in a large social network:longitudinal analysis over 20 years in the Framingham Heart Study, BMJ 2008;337:a2338 doi:10.1136/bmj.a2338) (How’s that for a serious reference?)

Well, Fowler and Christakis didn’t exactly say that happiness is infectious. That was what the free bus newspaper said in the pop-science report. But it doesn’t seem too far off the mark.

From the abstract:

Objectives To evaluate whether happiness can spread from person to person and whether niches of happiness form within social networks …
Results Clusters of happy and unhappy people are visible in the network, and the relationship between people’s happiness extends up to three degrees of separation (for example, to the friends of one’s friends’ friends). People who are surrounded by many happy people and those who are central in the network are more likely to become happy in the future. Longitudinal statistical models suggest that clusters of happiness result from the spread of happiness and not just a tendency for people to associate with similar individuals.

I’ll sidestep a long debate over their methods and conclusions* and just temporarily assume the conclusions are correct. Some of itheir data supports a standard “common sense” conclusion. If you are generally “happy”, you make people around you feel happier. Unhappy people make other people feel sad. Most people would agree on the basis of their own anecdotal evidence.

You could account for a lot of the effect through the processes of human interaction. We all spend most of our time communicating in one way or another. It would be strange if emotions expressed in our communications didn’t influence other people.

All the same, it’s a fascinating suggestion that emotions are being transmitted as if they were infections. “Memes”, maybe, although I don’t like using the term, except as a metaphor, and it’s far too easy for metaphors to get taken as literal truths. (Universe created in seven days, for instance.)

The BMJ article doesn’t suggest an explanatory transmission mechanism. This is disappointing, given that they have managed to come up with a measurable concept of “happiness”. Sort of sidestepping centuries of philosophical debate, really. Not invalidating it – a few indices can’t account for human consciousness – but approximating emotions in a quantifiable way, so the researchers could do statistical tests and chart their results.

Off the top of my head, I can guess at a few possible mechanisms – admittedly, all are crackpot theories, but they could be tested – such as people tending to synchronise their brainwaves with those of people they are close to; the action of pheremones; subconscious mirroring of others’ physical state, and so on.

Footnotes, even, as well as references.
* E.g Sampling factors that might have influenced the results included genetics (they focused on family groups), environment (living in a spatially limited area and, so, probably in the same social strata) and the tendency of people to associate with people that they identify with (they looked at friends.)