“Interaction design describes what happens in-between states. Unlike other disciplines, it’s focused on the change in state and not the state itself. Since the components of interaction are movement and time, it isn’t inherently suited for static artifacts like sitemaps, mockups, and visual treatments. Adjusting just one of these components has a great affect on what feels right. Today, I’ll explore how time changes user perception.”

Source: Guidelines for Animation Timing | Percolate Studio