  Behavioral economics show us that emotions play an important role in
individual behavior and decision-making. Does this also affect collective
decision making in a community? Here we investigate whether the community
sentiment energy of a topic is related to the spreading popularity of the
topic. To compute the community sentiment energy of a topic, we first analyze
the sentiment of a user on the key phrases of the topic based on the recent
tweets of the user. Then we compute the total sentiment energy of all users in
the community on the topic based on the Markov Random Field (MRF) model and
graph entropy model. Experiments on two communities find the linear correlation
between the community sentiment energy and the real spreading popularity of
topics. Based on the finding, we proposed two models to predict the popularity
of topics. Experimental results show the effectiveness of the two models and
the helpful of sentiment in predicting the popularity of topics. Experiments
also show that community sentiment affects collective decision making of
spreading a topic or not in the community.
