A study of more than a billion status updates from more than 100 million users of Facebook shows that feelings and moods are contagious.
The University of California, San Diego, research shows that positive posts beget positive posts and negative posts beget negative ones.
Apparently, the positive posts are more influential, or more contagious.
“Our study suggests that people are not just choosing other people like themselves to associate with but actually causing their friends’ emotional expressions to change,” said James Fowler, professor of political science, announcing the results of the study in the journal PLOS ONE.
“We have enough power in this data set to show that emotional expressions spread online and also that positive expressions spread more than negative.”
There is abundant scientific literature on how emotion can spread among people not only among friends but also among strangers or near-strangers.
However, little is known about emotional contagion in online social networks.
The researchers analysed anonymous English-language status updates on Facebook in the top 100 most populous cities in the US over 1,180 days between January 2009 and March 2012.
They relied on automated text analysis, through a software program called the Linguistic Inquiry Word Count, to measure the emotional content of each post.
Rainy weather, it turns out, reliably changes the tenor of posts, increasing the number of negative posts by 1.16% and depressing the number of positive by 1.19%.
To make sure rain was not affecting the friends directly, the researchers restricted analysis to friends who were in different cities where it was not raining.
Overall, according to the study, each additional negative post yields 1.29 more negative posts among one’s friends, while each additional positive post yields an additional 1.75 positive posts.
“It is possible that emotional contagion online is even stronger than we were able to measure,” Fowler said.
“For our analysis, to get away from measuring the effect of the rain itself, we had to exclude the effects of posts on friends who live in the same cities.
“But we have a pretty good sense from other studies that people who live near each other have stronger relationships and influence each other even more. If we could measure those relationships, we would probably find even more contagion.”
The researchers believe their findings have widespread implications.
Emotions, they write, “might ripple through social networks to generate large-scale synchrony that gives rise to clusters of happy and unhappy individuals”.
The researchers say:
“We may see greater spikes in global emotion that could generate increased volatility in everything from political systems to financial markets.”
They also suggest that their findings are significant for public wellbeing.
“If an emotional change in one person spreads and causes a change in many, then we may be dramatically underestimating the effectiveness of efforts to improve mental and physical health,” said Fowler.
“We should be doing everything we can to measure the effects of social networks and to learn how to magnify them so that we can create an epidemic of wellbeing.”
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