Animation, when done well, is fundamental to great user experiences. Whether it is hinting at what the user should do next or reacting or an action taken, animation has many uses. But how to do you do it right and make it feel natural? This great post from UX Collective has a huge list of super-helpful examples for beginners and experts alike.
Numerous researchers have discovered that optimal speed for interface animation is between 200 and 500 ms. These figures are based on the particular qualities of the human brain. Any animation shorter than 100 ms is instantaneous and won’t be recognized at all, whereas the animation longer than 1 second would convey a sense of delay and thus be boring for the user.
Use proper duration in your animation. Don’t make it too fast and don’t leave the user enough time to yawn (source: uxdesign.cc)