• by Erik Sass , Staff Writer @eriksass1, June 16, 2014

If you notice a lot of your Facebook friends are Debbie Downers you might want to give them the boot for the sake of your own mental health: new research published this week presents additional evidence that emotional states are contagious on social media, even in the absence of direct interpersonal interaction, confirming earlier studies of “emotional contagion.”

The latest study, titled “Experimental evidence of massive-scale emotional contagion through social networks” and published in the Proceedings of the National Academy of Sciences, focused entirely on the emotional content of news feeds for 689,003 Facebook users to see if moods can spread through simple exposure, without direct communication (for example through text messages or email).

The researchers tried to determine “whether exposure to verbal affective expressions leads to similar verbal expressions, a form of emotional contagion” -- that is, whether seeing a friend’s mood via the news feed prompted the user to create posts with the same emotional tone. To do this they conducted two separate experiments, one reducing the amount of positive emotional content in the users’ news feeds, the other reducing the amount of negative emotional content (emotional content was analyzed using Linguistic Inquiry and Word Count software). The study covered a total of three million posts containing 122 million words.

The study uncovered definite evidence that emotional contagion occurs on Facebook via news feeds, as “people who had positive content reduced in their News Feed, a larger percentage of words in people’s status updates were negative and a smaller percentage were positive. When negativity was reduced, the opposite pattern occurred.”

The researchers point out that the study also shows that emotional contagion can take place through text alone, without any kind of “non-verbal” communication (e.g. body language).  

As noted this isn’t the first study to examine whether emotional states can spread on social media. Back in March I wrote about another study, titled “Detecting Emotional Contagion in Massive Social Networks” and published in the journal Plos One, which analyzed around a billion Facebook posts by a million users -- then overlaid this sentiment with weather data showing when it was raining in a particular location.

After showing the correlation between bad weather and negative emotional states in rainy cities, they then examined how Facebook posts by users experiencing bad weather affected Facebook posts by friends in places with good weather. On average, a negative post from a person in a rainy area triggered a 1.29% increase in negative posts by Facebook friends living elsewhere, while each positive post triggered a 1.75% increase in positive posts. 

Likeminded people appear to gravitate to each other on social media. Last year, I wrote about a study by researchers at Beihang University, titled “Anger is More Influential Than Joy: Sentiment Correlation on Weibo.” The research team categorized around 70 million posts from 200,000 users on Weibo, a Twitter-like platform, according to sentiment, including anger, joy, sadness and disgust. Their analysis showed that Weibo users who post angry sentiments are more likely to be connected to other Weibo users who post angry sentiments -- making anger an “assortative” factor in the organization of online networks. The researchers also found that angry Weibo users are more likely to propagate angry sentiments via their networks.