In our second experiment, we investigate the correlation between sentiment and optimism / pessimism, and argue that sentiment analyzers, that are trained to predict sentiment (Liu, 2012;Pang and Lee, 2008), fail to detect optimism and pessimism.
we train several sentiment classifiers on the large SST and TSA sentiment datasets (described in Section 2) and evaluate the performance of these classifiers on the optimism/pessimism categories from the OPT dataset.