Online reviews promise to provide people with immediate access to the wisdom of the crowds. Yet, half of all reviews on Amazon and Yelp provide the most positive rating possible, despite human behaviour being substantially more varied in nature. We term the challenge of discerning success within this sea of positive ratings the 'positivity problem'. Positivity, however, is only one facet of individuals' opinions. We propose that one solution to the positivity problem lies with the emotionality of people's opinions. Using computational linguistics, we predict the box office revenue of nearly 2,400 movies, sales of 1.6 million books, new brand followers across two years of Super Bowl commercials, and real-world reservations at over 1,000 restaurants. Whereas star ratings are an unreliable predictor of success, emotionality from the very same reviews offers a consistent diagnostic signal. More emotional language was associated with more subsequent success.

Here is more from Matthew D. Rocklage, Derek D. Rucker, and Loran F. Nordgren, via the excellent Kevin Lewis.