Motivated by past efforts to exploit prior knowledge (Zhao et al., 2010;Lin and He, 2009), we use the OpinionFinder sentiment lexicon 9 (Wilson et al., 2005) to construct η i and η o .
terms w in the lexicon were given parameters η i w = η o w = 0.01, and other terms were given η i w = η o w = 0.001, capturing our prior belief that opinion-expressing terms are likely to be used in expressing positions.