According to Wikipedia, the spacing efffect means that “ Information is better recalled if exposure to it is repeated over a long span of time rather than a short one.”
Learning information can be easy: exposure is the key. If we’re exposed to information again and again, it will stick. That’s why I still remember those horrible WHAM songs from the eighties but I can’t tell you the plot from the movie that I saw last week, even though I loved it.
UX designers rely on the spacing effect when they work with ‘design patterns’. A design pattern is a re-usable form of a solution to a design problem. Users have learned to use these patterns because they see and use them everywhere online. That’s the spacing effect at work.
Do you always have to use design patterns? No you don’t, innovation wouldn’t exist if we never did anything different. But always ask yourself this question: ‘What’s the point?’. It’s pretty hard to learn new behaviour. Keep it easy for your audience unless you really have a good reason.