Being able to decode a person's emotional state--just by glancing at his or her face--would be a big boon to marketers. Now researchers think they've cracked the code, training computers to recognize not only facial expressions but also body language and other subtle cues. Here's a quick look at such research:
Can social media further this research? In the words of one researcher, "If you do an experiment on Facebook, you've got half a billion people in your sample."