Anger spreads faster and more broadly than joy, say computer scientists who analysed emotions on the Chinese Twitter-like service Weibo.
The research by Rui Fan and colleagues at Beihang University in China compared the way that tweets labelled with specific emotions influence other people on the network.
The results clearly show that anger is more influential than other emotions such as joy or sadness, a finding that could have significant implications for our understanding of the way information spreads through social networks.
In just four years, Weibo has attracted more than 500 million users who post around 100 million messages a day.
During six months in 2010, Rui and co collected some 70 million tweets from 200,000 users and constructed a social network in which users are linked if they mutually interact by sending messages to each other or re-tweeting each other's tweets, 'MIT Technology Review' reported.
To ensure that they only studied people who were strongly connected, Rui and colleagues only included people who had more than 30 interactions during the test period.
They determined the sentiment of each tweet in their database by analysing the emoticons they contained. They divided these into four categories, expressing joy, sadness, anger or disgust.
Finally, they studied the way sentiments spread through the network. For example, if one person sent an angry tweet, how likely was it that a recipient would also send an angry message, and how likely was it that the recipient of this message would pass on the same sentiment and so on.
The results were something of a surprise. When it comes to sadness and disgust, researchers found very little correlation between users. Sadness and disgust do not easily spread through the network in this way. They found a higher correlation among users who tweeted joyful messages.
But the highest correlation by far was among angry users. Researchers say anger strongly influences the neighbourhood in which it appears, spreading on average by about three degrees.
"Anger has a surprisingly higher correlation than other emotions," researchers said.