Animation is a great way to provide feedback to users, as
long as it’s both subtle and meaningful. Although animation
pervades iPhone OS, it is used to enhance the user’s
experience, not as the focus of the user’s experience.
- iPhone HIG, June 2008
Conveying a sense of kinetic realism is going to be a key
differentiator in next generation apps.
User Interface Design for iOS 7 Apps / Apple’s iOS 7 Tech Talk
Motion in the world of material design is not only beautiful,
it builds meaning about the spatial relationships,
functionality, and intention of the system.
Google Material Design
Animation> Authentic Motion
NUI - Brave NUI World
The Illusion of Life
Apple Human Interface Guide
Google Android Design Guide