Analysis of Experimental evidence of massive-scale emotional contagion through social networks

Kramer, A. D., Guillory, J. E., & Hancock, J. T. (2014). Experimental evidence of massive-scale emotional contagion through social networks. Proceedings of the National Academy of Sciences, 111(24), 8788-8790.

Key question

The key question this paper was trying to answer: does exposure to mood expressed in the News Feed on FB change the content people post (that reflects their mood changes)? Or in the authors own words, "whether exposure to verbal affective expressions lead to similar verbal expressions, a form of emotional contagion."

Why do we need this study?

Correlational studies cannot answer this question since it cannot support causality. Controlled experiments can support causality, but they have these problems:

  1. Exposure is not equal to interaction. In a controled experiment, mood change might come from interacting with a happy/sad person, rather than simply being exposed to that person's mood;
  2. Nonverbal cues are unavoidable in a controlled experiment, thus making it impossible for us to disentangle the effect of verbal cues.

Therefore, this study makes unique contributions to answering this question.

Study design


Measurements & Methods


Both H1 and H2 were supported. As can be seen in the figure, when negativity is reduced, people generate more positive words and fewer negative words, compared to the control group. The opposite patter occurred when positivity is reduced. It shows that emotions expressed by our friends through online social networks influenced our own mood status.

Some implications:

  1. Direct interactions were not necessary for emotional contagion.
  2. Seeing fewer friends' positive posts led people to produce fewer positive words in their own posts, rather than the opposite.


My thoughts

  1. It's interesting that in people's own status updates during the experimental period, only 3.6% were positive and 1.6% negative. However, for posts in people's News Feed, 46.8% were positive and 22.4% were negative. Why was it that News Feed posts were so much more emotional than people's own status updates? Is it because Facebook's algorithms likes to show more emotional contents to its users? I guess so.
  2. As the Editorial Expression of Concern and Correction said, it is "a matter of concern" that what we see on social media is to such a large extent manipulated by tech giants. As the study found, the content we see has an effect on our well-being. Even if they don't, users should be able to know what they are going through, rather than becoming a subject in an experiment we are ignorant of.