Well outside my field, but I believe this is a reasonably well-established problem in text processing/NLP, known as "Sentiment Analysis" - http://en.wikipedia.

Well outside my field, but I believe this is a reasonably well-established problem in text processing/NLP, known as "Sentiment Analysis" - http://en.wikipedia.org/wiki/Sentiment_analysis http://en.wikipedia.org/wiki/Sentiment_analysis My very brief google scholar search on that key phrase turned up a whole lot of results that look like they may provide fairly concrete algorithms and techniques for doing what you describe.