The spacing effect is one of many bits of science that Memrise uses to make learning as effortless as possible.
Here’s a quick explanation of what it is.
What is the spacing effect? Let’s compare two ways of learning. The first, massed repetition, is when you are repeatedly presented with an item to learn, in a short space of time. The second, spaced repetition, is when you are repeatedly presented with an item, but the repetitions are spaced out. As it turns out, spaced repetition leads to significantly better learning than massed repetition. This is called the spacing effect. The point is that the timing of your reviews makes a substantial difference to the payoff that you get from each review. Spaced out is better than massed.
How was it discovered? This effect was originally discovered by the German psychologist Hermann Ebbinghaus (1850 – 1909). Ebbinghaus created 2300 nonsense syllables and spent six years memorising random strings of them. He diligently tracked all aspects of his learning, and the spacing effect was one of the things that he discovered. The effect has since been replicated a number of times across a number of domains.
Why is the spacing effect the case? That the spacing effect is true is well established, but explaining why it is the case is still an open question.
One proposed explanation is that you are more likely to pay attention in spaced repetition than in massed repetition. If you are shown an item that you saw very recently (massed repetition), you are more likely to see it as familiar, redundant and boring, and so you’re not likely to give it your full attention. On the other hand, if you are shown an item that you last saw a while ago (spaced repetition), your memory of it will be weaker, and so your interest will likely be higher and you’re more likely to pay attention. Given that failure to pay attention is one of the main causes of forgetting, this seems like a plausible explanation of why spaced repetition is more effective than massed repetition.
A second proposed explanation of the spacing effect has to do with context. When talking about memories, context is the huge number of external and internal factors which are present when you form and when you subsequently review a memory. For example, your location when you review an item, the last time you ate, how anxious you feel — these are all part of your context. It’s been found that when you try to remember something, it is easier if your context is similar to what it was when you learned or reviewed it.
Now there is likely to be more fluctuation in context across reviews in spaced repetition than in massed repetition. This means that by using spaced repetition you associate more contexts with a memory and thus create more pathways from which to subsequently access it. The memory becomes robust because it is not tied to a particular context and so you can access it more easily.
Summary The spacing effect is the finding that spaced repetition generally leads to stronger memories than massed repetition. One explanation of this effect is that we pay more attention to material that we haven’t seen for some time, and a second explanation is that spaced repetition embeds an item in our minds across a larger number of contexts. The spacing effect is just one small part of the science behind how Memrise tries to make learning as easy as possible!
For a thorough literature review on the spacing effect and related issues see here.