Polarity classifications of writing samples are obtained by sentiment analysis operations including embedding each word of a writing sample into a word vector based on surrounding words, extracting one or more features of the writing sample, applying a feature learning function to the one or more features, estimating a polarity of the writing sample based on output from the word learning function and output from the feature learning function, and training the word learning function and the feature learning function based on a loss function relating the estimated polarity to the word vector to produce a model for writing sample polarity classification.