Expressive signals in social media languages to improve polarity detection

To capture the sentiment of messages, several expressive forms are investigated.Expressive signals enrich the feature space of baseline and ensemble classifiers.Only adjectives play a fundamental role as expressive signal.Pragmatic particles and expressive lengthening could lead to the de finition of erratic polarity classifiers. Social media represents an emerging challenging sector where the natural language expressions of people can be easily reported through blogs and short text messages. This is rapidly creating unique contents of massive dimensions that need to be efficiently and effectively analyzed to create actionable knowledge for decision making processes. A key information that can be grasped from social environments relates to the polarity of text messages. To better capture the sentiment orientation of the messages, several valuable expressive forms could be taken into account. In this paper, three expressive signals - typically used in microblogs - have been explored: (1) adjectives, (2) emoticon, emphatic and onomatopoeic expressions and (3) expressive lengthening. Once a text message has been normalized to better conform social media posts to a canonical language, the considered expressive signals have been used to enrich the feature space and train several baseline and ensemble classifiers aimed at polarity classification. The experimental results show that adjectives are more discriminative and impacting than the other considered expressive signals.