This quick TED talk entry is courtesy of TED.com. When are humans most happy? To gather data on this question, Matt Killingsworth built an app, Track Your Happiness, that let people report their feelings in real time. Among the surprising results: We’re often happiest when we’re lost in the moment. And the flip side: The more our mind wanders, the less happy we can be. (Filmed at TEDxCambridge.)