Computers may be good at crunching numbers, but can they crunch feelings?

The rise of blogs and social networks has fueled a bull market in personal opinion: reviews, ratings, recommendations and other forms of online expression. For computer scientists, this fast-growing mountain of data is opening a tantalizing window onto the collective consciousness of Internet users.

An emerging field known as sentiment analysis is taking shape around one of the computer world’s unexplored frontiers: translating the vagaries of human emotion into hard data.

This is more than just an interesting programming exercise. For many businesses, online opinion has turned into a kind of virtual currency that can make or break a product in the marketplace.

Yet many companies struggle to make sense of the caterwaul of complaints and compliments that now swirl around their products online. As sentiment analysis tools begin to take shape, they could not only help businesses improve their bottom lines, but also eventually transform the experience of searching for information online.

Several new sentiment analysis companies are trying to tap into the growing business interest in what is being said online.

Scout Labs, which is backed by the venture capital firm started by the CNet founder Halsey Minor, recently introduced a subscription service that allows customers to monitor blogs, news articles, online forums and social networking sites for trends in opinions about products, services or topics in the news.

In early May, the ticket marketplace StubHub used Scout Labs’ monitoring tool to identify a sudden surge of negative blog sentiment after rain delayed a Yankees-Red Sox game.

Stadium officials mistakenly told hundreds of fans that the game had been canceled, and StubHub denied fans’ requests for refunds, on the grounds that the game had actually been played.

But after spotting trouble brewing online, the company offered discounts and credits to the affected fans. It is now re-evaluating its bad weather policy.

“This is a canary in a coal mine for us,” said John Whelan, StubHub’s director of customer service.

Jodange, based in Yonkers, offers a service geared toward online publishers that lets them incorporate opinion data drawn from over 450,000 sources, including mainstream news sources, blogs and Twitter.

Based on research by Claire Cardie, a former Cornell computer science professor, and Jan Wiebe of the University of Pittsburgh, the service uses a sophisticated algorithm that not only evaluates sentiments about particular topics, but also identifies the most influential opinion holders.

Jodange, whose early investors include the National Science Foundation, is currently working on a new algorithm that could use opinion data to predict future developments, like forecasting the impact of newspaper editorials on a company’s stock price. (NYT)