Happy is as happy tweets. Those grumpy tweets you're sending from work might just be used as research to study American mood patterns. A group of Harvard and Northeastern University scientists have figured out who's happy and who's gloomy at certain times of the day by chronicling keywords used on the social media site, reports the New York Times... Here's what you had to say: Yana commented via Facebook: "Yes, Cali people are happier. The sun and beautiful weather, hello?" Shani wrote Facebook: "I'm very happy and I'm from Chicago. No sadness here at all."