  Recent studies suggest that human emotions diffuse in not only real-world
communities but also online social media. More and more mechanisms beyond
emotion contagion are revealed, including emotion correlations which indicate
their influence and the coupling of emotion diffusion and network structure
such as tie strength. Besides, different emotions might even compete in shaping
the public opinion. However, a comprehensive model that considers up-to-date
findings to replicate the patterns of emotion contagion in online social media
is still missing. In this paper, to bridge this vital gap, we propose an
agent-based emotion contagion model which combines features of emotion
influence and tie strength preference in the dissemination process. The
simulation results indicate that anger-dominated users have higher vitality
than joy-dominated ones, and anger prefers weaker ties than joy in diffusion,
which could make it easier to spread between online groups. Moreover, anger's
high influence makes it competitive and easily to dominate the community,
especially when negative public events occur. It is also surprisingly revealed
that as the ratio of anger approaches joy with a gap less than 10%, angry
tweets and users will eventually dominate the online social media and arrives
the collective outrage in the cyber space. The critical gap disclosed here can
be indeed warning signals at early stages for outrage controlling in online
social media. All the parameters of the presented model can be easily estimated
from the empirical observations and their values from historical data could
help reproduce the emotion contagion of different circumstances. Our model
would shed lights on the study of multiple issues like forecasting of emotion
contagion in terms of computer simulations.
