They relied on automated text analysis, through a software programme 'Linguistic Inquiry Word Count' to measure the emotional content of each post.
According to them, 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 among friends.
“It is possible that emotional contagion online is even stronger than we were able to measure,” Fowler noted.
The findings are also significant for public well being, said the study published in the journal PLOS ONE.
“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,” Fowler explained.
