Sentiment

There is a second closely-related term known as sentiment. The terms sentiment and emotion seem to be used in an ad hoc manner, with different writers using them almost interchangeably. Given the difficulty we have found in working out what emotions are, and in deciding exactly how many emotions there are, having yet another ill-defined term is not exactly helpful. To try to clarify the situation, note that when people work on sentiment mining, they generally make use of a simple, limited system of classification using positive, negative, and neutral cases. This is a much simpler scheme to process and ascertain, and yields results that are also easier to understand. In some ways, emotion analysis may be regarded as an upgrade to sentiment analysis; a more complex solution that analyzes much more than the simple positive and negative markers and instead tries to determine specific emotions (anger, joy, sadness). This may be more useful but also involves much more effort, time, and cost. Emotion and sentiment are, thus, not the same. An emotion is a complex psychological state, whereas a sentiment is a mental attitude that is created through the very existence of the emotion.

For us, sentiment refers exclusively to an expressed opinion that is positive, negative, or neutral. There is some degree of overlap here because, for example, emotions such as joy and love could both be considered positive sentiments. It may be that the terms simply have different granularity – in the same way that ecstasy, joy, and contentment provide a fine-grained classification of a single generic emotion class that we might call happiness, happiness and love are a fine-grained classification of the general notion of feeling positive. Alternatively, it may be that sentiment is the name for one of the axes in the dimensional model – for example, the valence axis in Russell’s analysis. Given the range of theories of emotion, it seems best to just avoid having another term for much the same thing. In this book, we will stick to the term emotion; we will take an entirely pragmatic approach by accepting some set of labels from an existing theory such as Plutchik’s or Russell’s as denoting emotions, without worrying too much about what it is that they denote. We can all agree that I hate the people who did that and I wish they were all dead expresses hate and anger, and that it is overall negative, even if we’re not sure what hate and anger are or what the scale from negative to positive actually measures.

Now that we know a bit more about what emotion is and how it is categorized and understood, it is essential to understand why emotion analysis is an important topic.