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Friday 28th October 2016

Happiness is infectious

9th December 2008

Emotion can ripple infectiously through social groups like a virus, according to US researchers.


A careful examination of data gathered among 5,124 adults suggests that a person's happiness depends upon the happiness (or unhappiness) of people they have never met, including friends of friends of friends.

If a friend living less than a mile away becomes happy, your chance of being happy increases dramatically. If a friend of a friend becomes happy, the probability you will be happy increases by about 6%.

The Harvard Medical School-led study found that happiness spreads within couples by an 8% probability increase, though the mood of work colleagues did not have an effect.

They studied the way happiness can spread among social groups by examining 53,228 social connections. James Fowler, a political scientist at the University of California, San Diego, led the new study along with colleague Nicholas Christakis, of Harvard Medical School.

He compared the findings to research showing that a US$5,000 increase in income would increase the probability of one's happiness by just 2%.

He said that even people we don't know and have never met have bigger effect on our mood than substantial increases in income. The participants had all taken part in the US Framingham Heart Study, which began in 1971 as a study of heart disease risk.

Participants in the study submitted data about their happiness every two to four years, measured by a standard psychological questionnaire.

Over several decades, participants were asked whether they took enjoyment from life, felt hope for the future, and whether or not they had a sense of self-worth.

All participants identified their close friends, relatives, workplace, and home.

Participants also updated researchers on their social contacts and health status.

Since many participants listed other study participants, Fowler and Christakis were able to connect social dots.

Fowler and Christakis used similar methods to document how obesity and cigarette smoking might ripple through the same networks of friends and relatives.

They found that, more than smoking and obesity, happiness is transmissible at close range.

A happy next-door neighbour increases the probability a person will be happy by 34%, and a sibling who lives within 1 mile (1.6 kilometres) by 14%.

The effect falls off through the network, and no effect can be detected beyond three degrees of separation. Professor Nicholas Christakis said the results imply that clusters of happiness occur not just because of a tendency for people to associate with similar individuals.

He said that the most important conclusion reached by the researchers is that peoples' health and wellbeing are inextricable from social networks in which one person affects another. Fowler theorises that beyond three degrees of separation, a kind of social interference pattern stops the transmission of behaviour.

Although the effect is comparable to the ripples created by dropping a pebble into a pond, it is also different. Fowler said that the effect is like having a handful of pebbles and throwing them into the pond at once.

As might be expected, both happiness and unhappiness are contagious by nature. Fowler and Christakis found that each happy contact increases a person's odds of happiness by an average of 9%, while an unhappy contact decreases those odds by 7%.

During the course of the study, they placed a bet over which emotion would spread with more efficacy.

Christakis admits to having lost the bet.


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