Emotions expressed on Facebook are contagious

(Image credit: Flickr CC By: Maria Elena)

last updated 8 January 2015

Emotions expressed on Facebook can be contagious, according to researchers at the University of California. Researchers studied the messages of more than 100 million users, and found that "emotional changes in one person caused emotional changes in another person."

The data, which was first published in the Wall Street Journal, showed that the number of negative posts increased 1.16 percent when it was raining, and positive comments dropped 1.19 percent. And when friends living in other cities where it wasn't raining read a gloomy message, their moods also darkened.

Posts were sorted by whether they contained positive or negative language, such as the word "sad" or "happy." To strip out the effect of topic contagion, the researchers removed any status updates that were actually about the weather. "We wanted posts where it is raining on you and it is making you write negative posts that are not about the weather," Dr. James Fowler said. [Wall Street Journal]

Since more than a billion people use Facebook, it's easy to see how an upbeat or downbeat mood in one place can quickly spread on the social network. "It is going to have implications for financial markets, which have bubbles and busts, and it has implications for political activity," Fowler said.