"Animation in software can serve a lot of important purposes. Animation can draw the user's attention, help the user build a mental model of navigation events, and indicate changes in state. But beyond all of those very functional ways that UX designers can employ animation in their work, it can also impact users on an emotional level: it can make your product seem happy, and ever so slightly alive."
http://uxmag.com/design/biological-motion-and-happy-interfaces
