  Most people consider their friends to be more positive than themselves,
exhibiting a Sentiment Paradox. Psychology research attributes this paradox to
human cognition bias. With the goal to understand this phenomenon, we study
sentiment paradoxes in social networks. Our work shows that social connections
(friends, followees, or followers) of users are indeed (not just illusively)
more positive than the users themselves. This is mostly due to positive users
having more friends. We identify five sentiment paradoxes at different network
levels ranging from triads to large-scale communities. Empirical and
theoretical evidence are provided to validate the existence of such sentiment
paradoxes. By investigating the relationships between the sentiment paradox and
other well-developed network paradoxes, i.e., friendship paradox and activity
paradox, we find that user sentiments are positively correlated to their number
of friends but rarely to their social activity. Finally, we demonstrate how
sentiment paradoxes can be used to predict user sentiments.
